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Report Information

Participants

Juan Manuel Alvarez, University of Idaho;
Steven Marquardt, North Dakota State Seed Department;
Rob Davidson, Colorado State University;
Jeff McMorran, Oregon Seed Certification;
Gary D. Franc, University of Wyoming;
Dan Hane Oregon State University;
Emmanuel Jacquot, INRA, Rennes, France;
Stacy Gieck, Oregon State University;
David Ragsdale, University of Minnesota;
Jonathan Whitworth, USDA-ARS, Aberdeen, Idaho;
Mike Thornton, University of Idaho;
Gary Secor, North Dakota State University;
Mark Pavek, Washington State University, Pullman;
Dallas Batchelor, Washington;
Phillip Nolte, University of Idaho;
Rajagepalbabu Srinivasan, University of Idaho;
Felix Cervantes, University of Idaho;
Hanu Pappu, Washington State University;
Jason Cavatorta, Cornell University;
Stewart Gray, USDA-ARS, Cornell University;
Cindy Nolte, University of Idaho;
Allan French, J.R. Simplot Food Group;
Alex Karasev, University of Idaho;
Rue Snell, Colorado Potato Certification Service;
Jim Crosslin, USDA-ARS, Prosser;
Phil Hamm, Oregon State University, Hermiston;
Andy Jensen, Washington Potato Commission;
Peter van Hest, Bejo Seeds, Inc.;
Luis F. Salazar, Agdia, Inc.

Brief Summary of Minutes

WERA-089 Potato Virus Disease Control Committee
Annual Meeting
14-15 March 2007
San Diego, CA

Chair: Juan Manuel Alvarez, University of Idaho, Aberdeen
Vice-Chair: James Crosslin, USDA-ARS, Prosser, WA
Secretary: Steven Marquardt, North Dakota State Seed Department

Chair Juan Manuel Alvarez welcomed everyone to the meeting and presented opening remarks regarding the format for the meeting and began the meeting with special introductions.

Greg Bohach (CSREES Administrator for our group) presented information regarding the reapproval of the committee and encouragement regarding the status of the organization and its continued recognition. The WERA-089 was approved almost immediately after last years meeting (one of 3 was rejected last year). The approbation process went through with no suggested changes where most that go through are with suggested changes. The impact statements were well received by CSREES.


Attendees represent the states of Colorado, Idaho, Minnesota, Oregon, New York, North Dakota, Washington, and Wyoming/Nebraska.

Certification Agencies Presentations and Reports

Rob Davidson (Colorado) talked about current and recent virus disease levels occurring in Colorado seed over the past several years and included several studies. Rob illustrated the dramatic increase of virus in seedlots when replanted for one and two years out from certification and the corresponding yield decreases with that rising virus level. He explained that in Colorado Certification, the first rejections for mosaic occurred in 1991, three years after the introduction of Russet Norkotah. There were no rejections for mosaic in the post harvest test until 2003, with the most acres rejected for the year and for the winter test in the 2006 crop. Russet Norkotah is by far the leading cause for rejections for certification in both summer and winter inspections. Until recently, rejections in other varieties had remained at a very low level but now they are starting an upward trend as well. Additionally, earlier generations are increasing in size in recent years and PVY has begun to become a problem there as well. The Russet Norkotah variety and selections represent 60% of the acres in the San Luis Valley, and about 45 to 50% of the seed acres. The aphid trapping data presented indicates rising numbers compounding with drought and cultural trends in other crops leading to increased numbers of aphids moving to potatoes. With the continued increase in inoculum, vectoring and seed demand, growers need the seed to fill contracts. This is where a seed law is needed. It will be difficult, but he believes that over the next two or three years they can get control over this. The difficulty has to do with the strains maturing later, and a roguer's ability to detect PVY anytime in a plant. It's not the vectors, it's the inoculum. Summary: The Russet Norkotah variety is problematic at best but most of the other varieties were pretty clean, although they are concerned about seeing the virus moving into the non- Russet Norkotah -type varieties. They have over 150 varieties. The only real problems are the mosaics and they are seeing more TRV in commercial acres (not seed). They may be reduced in acreage next year due to water availability. The certification system has been able to hold in check the various diseases afflicting seed potatoes. However, with a 'symptomless expresser' like Russet Norkotah, commercial demand and / or interference can pull the disease situation out of control if the hands of certification are tied.

Phil Nolte (Idaho) presented current year Idaho datasets provided by Doug Boze (ICIA Area Manager) regarding virus pressure and rejection rates and explained the changes taking place in Idaho regarding their post harvest test. The virus levels in the 1990s were PLRV until acreages of Shepody and Russet Norkotah increased. Then PVY levels began to ramp up and are currently a problem. The worst years were probably 2000 and 2001. The current year winter test is not complete. According to Alvarezs suction trap data, mid-July to 1st of August is usually when a spike of Bird Cherry Oat Aphids occurs. Leafroll is very minimal. In 2006, they had the highest aphid activity in the last four years and the virus level may increase consequently.

Steve Marquardt (North Dakota) presented various data sets from ND, WI and ME ranging from 1968 including summer and post harvest test inspections. Rising and falling rejection levels in line graphs were noted for several diseases, virus and non-virus. They rose and fell with time. All of the inspections are done on a visual basis with laboratory testing for support information, especially for 'symptomless expressers'. In general, PVY levels are rising and becoming more difficult with the new strains and milder symptoms on many varieties, but it is manageable.

Discussion ensued regarding the importance of the PVY problem. Consensus seemed to be that there is an increase of PVY infection rates. Several other topics in the discussion included whether the PVY epidemic is a problem of varieties that do not express symptoms adequately and / or a problem that the newer PVY strains do not seem to express visually for as long in the season (narrowing visual window), and that the yields are not always dramatically affected. It was not a problem until the commercial growers found that they could not get seed. As long as seed is available and there are no apparent symptoms, the perspective of the commercial grower of Russet Norkotah seems to be that, PVY is not a problem to them. They will have taken the cap off the virus. This is another problem that needs to be addressed. Clearly, PVY is a problem. But the strains are another issue as they may present different outcomes when infecting different cultivars. It was especially noted the case of Russet Norkotah selections, presenting milder infection symptoms with not major yield reductions. There is still a lot to learn about the new virus strains. As was acknowledged by many, earlier generations of seedlots are increasing in size in recent years, which makes not them practical to rogue. It is necessary to look for virus management / control strategies that we can take back to our grower / board / commission meetings for further consideration as they get final say in rulemaking on the state level. Are there levels of virus that our current standards or techniques cannot manage? One of the problems is the varieties, but we do not have the ability to control that. There is a limitation to what growers and certification can do. We cannot spend a fortune testing for every combination of variety and strain and end up with nothing meaningful. It's a visual based system and the ability of roguers is variable, but we have studies showing that a good roguing crew can stay on top of it. Additionally, other non- Russet Norkotah varieties out there have PVY problems. So it's more problematic than a laboratory can resolve without the insight of the people in the field.

Dave Ragsdale (Minnesota) presented some data indicating the current situation in Minnesota. PVY strain information illustrated a complicated picture in Minnesota. Fungicide use for late blight exacerbates green peach aphid flights in the field. Fungicide and pyrethroid sprays in combination balloon huge populations. He has seen circles killed by green peach aphid. Minnesota had suction traps and pan traps for the past three years in Hawaii. It may be 12 aphids for the six week period. Aphis gossypii and Aphis glycines, in the field can mate. They are very closely related. Although soybean aphids (A. glycines) do not colonize potato, they do feed on the phloem for as long as 10 to 12 minutes. Minnesota had a very mild winter translating into early aphid movement. They are watching movement of virus strains. Virus levels seem to be high. The rejection rates did increase.

Jeff McMorran (Oregon State University). Very low levels of PVY were observed this year in winter grow-outs relative to 2 or 3 years ago. This is attributed to a couple of different factors: 1) growers are replacing seed with clean seed and it stayed clean 2) they are growing some Russet Norkotahs, but not a lot of acres of the varieties that cause them a lot of problems in the past. Growers are moving away from some of the problematic varieties. They are seeing more mild-type symptoms.

Gary Franc (University of Wyoming, Wyoming / Nebraska). 5700 acres certified last year, no rejections for PVY. About 500 of those acres are in WY and all acres in WY are certified, even though a portion of those acres are just for the commercial market. No real problems the last couple of years.

Dallas Batchelor, Andy Jensen (Washington). Most of the seed is confined to the west side of the state. The east side has a few growers in the northeast, but most of that is consumed internally. Commercially, it has been quite a few years since leafroll has been of any consequence, however, the last 2 years have seen a steady increase of leafroll plants observed. They believe that they will see a resurgence in leafroll in the very near future. Spraying for leafhoppers has been stepped up. Andy Jensen put out the yellow cards for monitoring leafhoppers. Jensen indicates that they do not colonize (in terms of reproducing) potato plants, but they are consistently found on potato fields for quite some time. There is data that says that in the lab they feed on the plants for weeks. So, presumably, you can spray with some residual activity, you can knock them out for some time. It takes several minutes to hours to spread the phytoplasmas. So if the insects feed for anytime, they will probably spread the phytoplasmas that cause the disease. It appears leafhoppers are not afraid to stay for days on the crop. They think the insects have 3 generations per season. Question: Do you spray 3 times, only in spring or only when they move from weeds to potatoes? Some growers spray once, some all season. There are some that think the insects produce damage all through the season. But, from a grower's meeting, they put down almost anything from mid-May to almost the 3rd week in June and get good control but there are those who continue to see additional infection beyond that and how important that is no one seems to know. If you look at the symptomology, its about 3 weeks from infestation to symptoms. Jim Crosslin: The data that exists (Munyaneza) with row cover in Moxie and uncovered at various times definitely indicates that it is the early crop exposure to the phytoplasma vectors is when the plants are most susceptible to infection. The older plants are less susceptible. So, control of leafhopper in early May to possibly early June is fairly good to control purple top. The early leafhopper invaders are the ones that transmit early in the life of the potato plants causing the disease problems. It is now also known from leafhopper colonies that the insects overwinter as adults with the phytoplasma in them. So as soon as it warms up in March, they will move into whatever plants happen to be available and will have phytoplasmas in them ready to be vectored. They find phytoplasma in tumble mustard, wild radish, but never found it in Russian thistle until last year. Russian thistle is a great host for the leafhopper. They have infected kochia in the greenhouse, but have never had a wild kochia test positive for phytoplasmas.

Discussion: Growers mostly use pyrethroids and the carbamate Vydate. Vydate is used in furrow in the growers nematode program but it is much more expensive than pyrethroids. Someone may have seen some effectiveness of this insecticide reducing phytoplasma infection by accident. It was noted that: the earlier the phytoplasma infection, the more devastating the disease. After plants reach maturity, you may or may not see signs of infection. It all depends on the physiological stage of the crop. The processing quality does not seem to deteriorate at that point in time. There is a yield loss. The most efficacious control of phytoplasma vectors is about 4 weeks after plant emergence. [Crosslin: The phytoplasma does infect the daughter tubers at a fairly high rate (looks like about 35% on controlled, unsprayed plots) and fairly high rate (20%) of those tubers will produce a phytoplasma-affected plant with no symptoms, esp. in the potato variety Katahdin].

Other Disease-Related Presentations

Emmanuel Jacquot (INRA). Reported on the Detection and Characterization of the Potato virus Y using FRITN (Fast Reliable Innovative Tools for Necrotic Potato Virus Y) Assay
and Potato virus Y: A variable pathogen with numerous not yet described variants. The invited speaker presented an overview of the current PVY detection tools, indicating that the serological tools are not reliable for detection of the virus and that they fail to characterize the different strains. Then he also presented some biological and molecular tools for PVY detection and characterization. Biological tools, he argued, are reliable for characterization of strains but inappropriate for large scale testing. Recombination events that occur in molecular targets used by molecular assays may make these tools inefficient for strain characterization. Then he presented some molecular markers that are related to the necrotic ability of the different PVY strains. A new set of detection tools based on these markers have been patented by his lab in France. There are qualitative, quantitative and multiplex versions available. The FRITN PVY assay targets a single nucleotide polymorphism linked to the necrosis property of PVY isolates. FRITN assay allows accurate assignment of the 46 tested PVY isolates in their corresponding YN or YO groups. Samples containing PVYN or PVYO RNA copies are efficiently detected by the developed FRITN assay. Detection of PVYN and PVYO isolates in mixed fractions is reliable using the FRITN assay. The quantitative FRITN assays are 10 to 1000 times more sensitive than available molecular and serological assays and allow detection and quantification of PVY in fractions containing from 103 to 107 copies of PVYN or PVYO RNA. The quantitative FRITN assays quantify PVY isolates according to the specificity of the probe. In mixed samples, the specific quantitative FRITN assays quantify the target copy number whatever the YN/YO ratio. From GH to diagnostic you can perform 200 tests in 1/2 day on leaf tissue. Add 1 to 2 hours for tubers. These are detections from total RNA extractions. They have not checked these assays against isolates from our hemisphere. Cost is approximately 4 to 10 times that of ELISA. He would like to coordinate a worldwide project to characterize all isolates with the assay and confirm the necrosis-causing gene. As with most tests, it is not as reliable before dormancy is broken. The extraction method is not yet developed to use this technique to test plants a week before kill date.

Luis Salazar (Agdia, Inc.) presented some new information from Agdia, Inc. regarding the availability of a new lateral flow test. With emphasis on the Immunostrip tests, Luis Salazar was placing focus on accuracy rather than sensitivity. They are working to include all the common potato viruses. Future plans are in this area. They are also developing rapid detection technology for TRV without coat protein. The NASH technique is also being developed for commercial use at Agdia. This may be more accurate than PCR. PCR requires an extraction which may be given to lose some of the target.

Stewart Gray (USDA-ARS, Cornell U.) gave an update on the 3-year national PVY survey. There is data for 2 years completed. There are 4 PVY groups now: PVYO, PVYN:O, PVYN, and now PVYO5. PVYO seem to be the predominant isolate in most states. PVYN:O is widely distributed and seems to be spreading. In some of the states they are seeing a shift of strains but the PVYNTN seem to be localized and stable. Most lots have low or undetectable levels of PVY infection but with the very low number of tubers per acre (2), more data are needed. The Canadians are finding the same things in Canada. PVYN:O is being seen more now locally than nationally. Theories were that 1) perhaps that more of the tubers are infected per plant, and that 2) aphids transmit the new PVY recombinant strains more easily, but neither of the theories have been proven. He does not know whether the mild symptoms produced by some strains allow more infection in the system. The high level of virus infection seems to him to be more environment- than cultivar- dependant. Perhaps some kind of competitive advantage, but it is not clear what it is. Rangers now live longer, and aphids seem to be unable to transmit PVYO after acquiring PVYN:O, and the reverse is not true. Science Panel recommendations included: dropping the P1 sequence information, and simply going with the multiplex information; discontinuing the Year 2 testing, managing PVY as a species not as strains, making post harvest lab-testing mandatory, developing national standards for PVY tolerances, and sharing more information between the US and Canada.

Jason Cavatorta (Cornell University) talked on the lack of availability of PVY-resistant varieties to growers, even though there are some known sources of PVY resistance. A number of resistance genes have been introgressed into varieties. There are a number of tolerant (Shepody) and resistant varieties (e.g. Eva, Cornell University, bred for GN resistance). In addition to conventional resistance, there is also transgenic resistance that includes pathogen-derived resistance such as coat, replicase, and other resistance such as antiviral proteins from pokeweed, plantibodies targeting protease in the plant. Transgenic resistance, however, has a strong consumer rejection at this time. He presented an approach that for transgenic resistance using only potato DNA (intragenic) which may be more accepted for consumers and could be more durable.

Babu Srinivasan (University of Idaho) talked about an alternate host and possibly a different biotype of potato aphid (PA) which may influence the epidemiology of PVY. Hairy nightshade (HNS, annual solanaceous weed) is found everywhere in Idaho and the Pacific Northwest. Studies to evaluate the performance of the PA on different host plants were undertaken. Host plants included HNS, potato, ground cherry, Chinese cabbage and wild rose and it was found that the aphid does very well only on HNS. HNS outperformed any other host plant. This finding was not expected considering that this aphid is a highly polyphageous. Field experiments also demonstrated the preference of PA for HNS. Virus transmission experiments found that HNS and can be infected with PLRV and PVY. Additional experiments were conducted to determine the effect of plant host and viral infections on the biology of PA. Longevity of PA was longer on HNS when compared to potato and even longer on infected plants when compared to non infected plants of both species. Fecundity was higher on PLRV infected plants of both species than on healthy plants. In fact, PA did not survive to reproduce at all on potato plants. Summary: The PA lives longer and produces more nymphs on HNS than on potato. PA lives longer and produces more nymphs on PLRV-infected plants than on healthy plants. Virus infection alter the physiology of the plant making it more conducive for the PA survival. Andrew Jensen confirmed species identity of this colony as PA. However, since PA did not survive on potato plants, it is believed that this is a new PA biotype exclusively adapted to HNS. 80% of the nymphs turn into adult winged aphids making PA a more effective virus vector. PA is also more active than GPA. Survives less on potato plant, but probes more. PA transmits several strains of PVY. HNS could be one of the causes that we see so much inoculum at the end of the season. Since HNS is an excellent plant host for green peach aphid and PA, and also harbors potato viruses, it should be considered in the management plan of potato viruses. Luis Salazar commented that phloem parenchyma cells are infected by leafroll when co-infected by PVY or PVX.
Jonathan Whitworth (USDA-ARS, Idaho) provided information on the Canadian Quality Assurance Survey (CQAS). This survey was developed from discussions held during the negotiations of the Virus Management Plan. Due to the change in Canada of shipping point inspections being done under an audit system instead of a direct federal inspection on every load, USDA-APHIS made plans to randomly check incoming seed loads for the presence of PVYN strains. This work was initiated last April after the WERA89 meeting using some year-end money from APHIS with support from the National Potato Council. Jim Crosslin, Jonathan Whitworth (both USDA-ARS) and John Rascoe (Agdia) developed a check set of PVYN tubers that were tested in all three labs. Results were used by Crosslin and Jim Lorenzen (Univ. of Idaho) to make adjustments to the S6 Singh primer for RT-PCR. A modified S6m primer was subsequently used by Agdia this year on a new check set of tubers. The new primer was able to detect PVYN in the check tubers and is now being used by Agdia (Elkhart, IN) and STA labs (Gilroy, CA). Whitworth provided results of the testing process and made available a list of labs and people for each state that would be involved in the CQAS. This program provides money for testing imported Canadian seed lots with a receiving point inspection that evaluates tubers for internal necrosis and collects a sample of tuber stem ends for a bacterial ring rot test. The money comes from APHIS through a TASC (specialty crop) grant. The work that has been done now provides seed growers and agencies with commercial labs (AGDIA and STA) that can test tubers for PVYN strains as well as Tobacco Rattle Virus, Alfalfa Mosaic Virus and other tuber-necrosing viruses.
Hanu Pappu (Washington State University) reported on the continuation of a study of a necrotic reaction of Defender to PVS. Originally found in 2003 in Othello in potatoes in the Washington State seedlot trials from MT in 2003. Some plants exhibited a very severe necrotic type of response on potato and these symptoms persisted in 2004, 2005, and 2006. Symptoms also included severe stunting, necrotic lines, some necrosis on the leaves and sometimes severe malformation. It was interesting that these symptoms are only in one cultivar, Defender, which is one cultivar fully resistant to late blight. For a number of reasons, it is not a popular commercial variety. ELISA and PCR were employed to find out what viruses were involved. Jonathan Whitworth contributed some work to this project in 2003 and 2004. The samples were positive for Potato Virus S and no other common viruses were detected. Interestingly, nearly 80% of the Defender lots and 50% of the Ranger Russet, Russet Burbank and Shepody were positive for PVS. While Defender displayed severe reaction to PVS infection, all other cultivars showed very mild or no symptoms at all. Most were asymptomatic. The tubers were collected thanks to Mark Pavek in the seedlot trial and then grown in the greenhouse to confirm tuber infection. The symptoms persisted, most were symptomless, some with symptoms, but again all plants tested positive for PVS with PCR. Defender symptoms could be described as a hypersensitive response. The analyzed virus is a typical carlavirus. The sequence data achieved so far will be used to generate new RNA and reinfect Defender plants to prove that it is the sequence causing the necrotic symptoms. Hopefully changes can be made in the RNA genome and determinants that are responsible for this differential host response in Defender can be found. Sequences related to the Defender isolate in the Genbank, show that the closest one is reported from Germany. Purification of the virus is in progress and, of course, the ultimate test would be to make an infectious clone. It was noted that parentage of Defender involves a Polish cultivar. These symptoms are reminiscent of Colletotrichum spp. PVS is usually benign. 50% of all Norkotahs and Shepodys are positive for PVS, with very few symptoms.
Stacey Gieck (Oregon State University). PMTV and powdery scab (Sss) survey. PMTV is vectored by Spongospora subterranea f. sp. subterranea, the causal agent of powdery scab, and was 1st reported in the United States in 2003 by Lambert et al. (Plant Disease 87:872) from samples collected in Maine. Since then PMTV has been reported by Xu et al. (Plant Disease 88:363-367) from tubers entering Canada from the US but the states were not identified. However reports from APHIS identified nine states. Given the way the Canadian samples were taken, PMTV likely is widespread but obviously not causing symptoms. The objectives of the study were to confirm the occurrence of PMTV, determine similarities /differences in isolates from different geographical areas that might help explain, if the virus is widespread as suggested why internal tuber symptoms have not been widely found. The methods to determine the presence of PMTV were two-fold; one, test tubers with internal symptoms and or powdery scab sent to the laboratory for diagnostic services and, two, bait soil using tobacco where the roots become infected with powdery scab and then PMTV if present. Samples were tested by RT-PCR for PMTV using Crosslin primers targeting the coat protein region of the RNA3 and powdery scab. Tubers positive for PMTV have been confirmed from 4 states. Soil samples have confirmed PMTV from most of those states. Jim Crosslin will look at sequence comparisons of different isolates. Jonathan asserts that PMTV is A2: regulated quarantine pest: present, but under official control. NAPPO: non regulated pest. Purpose is to study and understand the pathogen. Not seeing symptoms of any consequence.
Gary Secor (North Dakota State University) reported on Zebra Chip (ZC). 3 different synonyms: US=Zebra Chip, Mexico=papa manchada (stained), Guatemala=papa rayada (striped). Update: 20-30 scientists involving plant pathologists and entomologists are now working on this project. Almost $500,000 from many sources: FritoLay, Sabritas, growers, USPB, NPC, USDA-ARS.. Some of this work has been done by Joe Munyaneza. Scientists are looking at the cause, spread, source, and control. It appears to be spreading not only in the US (CA, NM, TX, CO, KS, southwestern states) but in Mexico, and Central America. It is not in the seed-producing states, neither in Florida or Missouri. The disease is detected based just on symptoms. This is the leading cause for rejection of potatoes for processing into chips and tablestock because of the impact on quality. The disease has been seen since 1995 but really in earnest since 2000. Foliar symptoms are similar to purple top wilt symptoms and include: twisted stems, stunted plants bushy in appearance with a little yellow or purple in the top growth, severe wilt of stems, broken nodes and axillary buds, swollen nodes, and the zigzag appearance. Wilting, often scorching on the leaf edges. There may be brown vascular discoloration and plants could be killed by infection. Underground symptoms include collapsed stolons, lenticel proliferation of the underground stem (indicating some water relations problems), a remarkable pink, sunken stolon attachment like a pink belly button, brown discoloration of the medullary rays throughout the entire length of the tuber (this symptom differentiates the disease from all the other diseases), and affected plants are susceptible to secondary infections by Fusarium and/or Erwinia. The infection causes browning of chips when potatoes are processed. Sugars accumulate and caramelize at high temperatures. We call it zebra chip because of the light and dark streaks. Stems are discolored internally (vascular elements). All the processing and tablestock varieties we have looked at in Mexico, Guatemala and Texas are susceptible. Occurrence has been as high as 70% of affected plants in the field in Mexico and Guatemala. In the US (TX) we usually see from 2 to 5 % in the field. We have not seen an immune variety yet. European varieties, Alpha, Yukon Gold, Red LaSoda, Russet Norkotah, all Frito-Lay (FL) varieties, public chipping varieties all are susceptible. ZC has become the leading cause for rejection of chipping potatoes not only for FL but for the local chippers as well. It is the leading cause for tablestock rejection in Mexico. Experiments in Guatemala covering rows with insect proof cloth seem to prevent infection. This probably indicates an airborne vector. Insect scouting has been extensive. We usually see symptoms by 75 days after planting. 30 to 45 days after planting is probably the time of infection. But we think infection occurs early in the season. The only insect associated with ZC at this time is the psyllid, Bactericera cockerelli (Sulc). Psyllids have been recorded from Guatemala all the way up to Alberta Canada and back as far as the 1920s. We don't know if it's toxin or not. Reversion of symptoms was seen in Guatemala spraying tetracycline in fields. When they stop spraying, the symptoms come back. They did find it in the seed production area of Baja California for the first time in 2006. It appears to be independent of seed source. Affected eyes produce really weak plants. We don't know the epidemiological importance of affected seed. It was seen in 2005 in volunteer Red LaSodas in Texas. Eliminated: all the soilborne pathogens (rhizoc., nematodes, etc.), and viruses (PCR tests all negative). All tubers from affected plants show symptoms, but occasionally a plant where a few tubers don't have symptoms can be found. It is graft-transmissible producing typical symptoms in the greenhouse for multiple generations. Therefore, toxin and physiological disorders can be eliminated as the cause. Xyllela is not a cause of this disease even though it may be present. Many phytoplasmas have been found associated with this disease. We do not have a control in the field except insecticides. Admire at planting and Oberon (new insecticide for psyllid nymphs and whiteflies from Bayer) in the field: this is a new push from growers. We have not found psyllid yellows with this ZC tuber symptom. Scanning and transmission EM reveals good populations of bacteria in phloem. It looks a lot like a proteobacteria present in a disease on sugar beets or strawberries. They have now cut back on the cause to focus on control. ZC is limited to the SW possibly because that is the range of the vector. Solke deBoer tested for viroids and it's negative. Some testing of psyllids and sharpshooters was done but nothing definitive.

Jim Crosslin (USDA-ARS, Prosser) presented more Zebra Chip information gathered last year with Joe Munyaneza covering trials. Sequentially grafting experiments (transmitted 3 times into potatoes from plants from Pearsall, TX) were conducted. He saw symptoms consistent with psyllid yellows or ZC with the severe scorch. However, after 3 transmissions he had contamination and had to throw out. Psyllids were originating from Dalhart, TX. All psyllid colonies identified in Beltsville. After slicing, the tuber necrosis appears before your eyes. The symptoms can be reversed if the psyllids are killed before a certain point. On tomatoes in CA, their economic threshold for psyllids is 3 nymphs feeding for a week. Frito first saw this in 1994 in Mexico. Hoba production is new in that McAllen TX area. They have found that an overwintering host is wolfberry (solanaceous tree). The psyllids are all positive for Carsonella (endosymbiont), but they don't think that's a factor. Wolfberry is in Pearsall, Weslaco and McAllen, unknown if its in Dalhart. It is still unknown if we're looking at toxemia or some unknown pathogen. The grafting experiments suggest that there may be a pathogen present. It has been reported that there are fields full of psyllids without ZC and fields with no psyllids that have ZC. There may be some other factors involved. No inclusion body data. IM Lee has done a fair amount of EM work but inconclusive. Two psyllid biotypes are known in the US and 1 more in Guatemala.

Phil Hamm (Oregon State University) talked about the further understanding of the Corky Ringspot Disease. The symptomatic tuber arcs are diagnostic but smaller spots can be confused with AMV, TSWV, PMTV, PVYNTN or N:O and Internal Brown Spot (IBS). Aerial field infrared photos show open areas with bare soil, and some not well populated with plants. The plants are not dead but poor growth. Distortion on these plants, irregular sprouting, and multiple stems before emerging, were the symptoms observed. Herbicide damage was suspected. The plants with yellowed leaves were thought to be AMV but tested negative, then noticed chevrons. In another field in Pasco WA: areas very poorly populated with plants. There were distorted plants but no foliar symptoms. Grower used a Vydate program and got him by. Symptomology will give a little bit of an impression it might be rhizoc. Tested nematodes and did find them viruliferous. TRV typically has 2 particles. In potato leaves, they found both particles only once. In roots both particles were found most of the time. Confirming virus presence is not practical with ELISA as it loses its coat protein. Now we use the PCR technique. Roots have both RNA1 and 2 but leaves with RNA1 only. In greenhouse studies, only one was ELISA positive. Tubers usually only have RNA 1, too. (Crosslin: in about ten years, approximately 50% of TRV-positive tubers have only RNA1s.) Methamsodium and Telone II is the program to use at present. TRV and the nematodes have wide host ranges, but the 2 don't mix with weed-free alfalfa. Controls for CRS: don't grow potatoes, rotate with weed-free alfalfa, preplant Telone II the fall before, and in-furrow Vydate at planting to control TRV in potatoes. The nematode spreads TRV so early in the season that you can't control it if you don't have Vydate in furrow. Symptom only reported in Colorado about 10 years ago by Pete Thomas. Need to relate nematodes to early feeding symptoms and number of the viruliferous nematodes related to those early symptoms. Incidence seems to be increasing. Actually, it looks like PMTV with nice chevrons but when they were sent to us they were TRV.

Accomplishments

Title: Identifying the components of the tuber necrotic complex.<br /> <br /> Issue: Identifying the various components of the tuber necrotic complex and developing new molecular diagnostic tools for diagnosis and separation methods and protocols have been accomplished for detection and diagnosis of a heterogeneous group of viruses with overlapping symptoms; 3 different vectors require 3 different control strategies. Diagnostics are limited to scope of the diagnostician's experience without being able to definitively identify pathogen/s. Improperly diagnosed diseases probably have been allowed to be in the system without knowledge. Improved diagnostic tools should help growers make better informed decision leaving less risk to an unknown factor.<br /> <br /> What has been done: The Canadian quality assurance program uses recommendations from the WERA089 group and also modified primers for detection of PVY strains allowing commercial labs to reliably detect these pathogens, without which the program could not exist. Labs are now able to check for these pathogens providing assurance of quality seed to and empowering the industry receiving this seed to effectively take the appropriate control measures if a pathogen is present.<br /> <br /> Impact: Improved diagnostic tools will allow heightened confidence in the diagnoses of viruses when high seed volumes move interstate for recertification and for commercial planting as well. Internal necrosis due to PVY cannot be used for planting commercial potatoes, the PVY survey and the Canadian quality assurance survey will provide information about the health status of the seed. New patented tools presented at the meeting (FRITN assay) may be useful to reliably identify necrosis factors of the PVY strains and perhaps levels of infection in seedlots, regions or environments associated with specific cultivar/virus strain combinations in a given environment.<br /> <br /> Funding sources: State potato commissions, Hatch, National Potato Council (NPC), National Potato Board (NPB), numerous potato growers. <br /> <br /> Title: Effect of vectors and alternate inoculum sources in the epidemiology of viruses and the PVY complex. <br /> <br /> Issue: Identifying the various components of the potato viral pathosystem and studying complex intricate interactions between the components with special emphasis on alternate vector reservoirs and inoculum sources and their role in the epidemiology of viruses. The objective of this work is to identify the additional inoculum sources and determine the role of these sources in the epidemiology of the viral diseases. Preferences of vectors for infected plants and weed hosts suggest a possible enhancement of pathogen spread in field. Laboratory studies show that the fecundity of the potato and green peach aphids may be significantly higher on mixed-infected plants than on singly-infected plants or non-infected plants. <br /> <br /> What has been done: Numerous alternate hosts that serve as vector and virus reservoirs have been identified. The importance of the involvement of the alternate host, hairy nightshade in aphid vector epidemiology of PLRV and PVY is becoming apparent.<br /> <br /> Impact: The importance of managing the alternate hosts is strictly recommended to be a part of any devised virus management plan primarily by collaborating with state commodity commissions, agricultural departments and seed certification agencies. Recommendations for nightshade control have been developed and published. <br /> <br /> Funding sources: State potato commissions, Hatch, National Potato Council (NPC), National Potato Board (NPB), numerous potato growers.<br />

Publications

Agindotan, B.O., P.J. Sheil, P.H. Berger. 2006. Simultaneous detection of potato viruses, PLRV, PVA, PVX and PVY from dormant potato tubers by TaqManÒ real-time RT-PCR. Journal of Virological Methods, (In Press). <br /> <br /> Alvarez, J.M., F. Menalled, and M.A. Hoy. 2006. Molecular tools in biological control. (in Spanish). Forum article in Revista Manejo Integrado de plagas y Agroecología, 74: 4-11. <br /> <br /> Alvarez, J.M. and P.J.S. Hutchinson, 2005. Managing hairy nightshade to reduce potato viruses and insect vectors. Outlooks on Pest Management Journal, 16 (6): 249-252.<br /> <br /> Alvarez, J.M. and R. Srinivasan. 2005. Evaluation of hairy nightshade as an inoculum source for the aphid-mediated transmission of potato leafroll virus. Journal of Economic Entomology. 98: 1101-1108. <br /> <br /> Crosslin, J.M., P.B. Hamm, D.C. Hane, J. Jaeger, C.R. Brown, P.J. Shiel, P.H. Berger, and R.E. Thornton. 2006. The occurrence of PVYO, PVYN, and PVYN:O strains of Potato virus Y in certified potato seed lot trials in Washington and Oregon. Plant Dis., 90:1102-1105.<br /> <br /> Crosslin, J.M., G.J. Vandemark, and J.E. Munyaneza. 2006. Development of a real-time, quantitative PCR for detection of the Columbia Basin potato purple top phytoplasma in plants and beet leafhoppers. Plant Dis., 90:663-667.<br /> <br /> Goolsby, J.A., B. Bextine, J.E. Munyaneza, M. Setamou, J. Adamczyk, and G. Bester. 2007. Seasonal abundance of sharpshooters, leafhoppers, and psyllids associated with potatoes affected by Zebra Chip disorder. Subtropical Plant Science (in press).<br /> <br /> Lee, I.-M., K.D. Bottner, J.E. Munyaneza, R.E. Davis, J.M. Crosslin, L.J. du Toit, and T. Crosby. 2006. Carrot purple leaf: a new spiroplasmal disease associated with carrots in Washington State. Plant Dis. , 90:989-993.<br /> <br /> Lee, IM, KD Bottner, GA Secor and VV Rivera-Varas. 2006. Candidatus Phytoplasma americanum, a phytoplasma associated with a potato purple top wilt disease complex. Int. J. Syst. Evol. Microbiol., 56:1593-1597. <br /> <br /> Lorenzen, J.H., T. Meacham, P.H. Berger, P.J. Shiel, J.M. Crosslin, P.B. Hamm, and H. Kopp. 2006. Whole genome characterization of Potato virus Y isolates collected in the western USA and their comparison to isolates from Europe and Canada. Arch. Virol., 151:1055-1074.<br /> <br /> Munyaneza, J.E., J.M. Crosslin, and J.E. Upton. 2007. Association of Bactericera cockerelli (Homoptera: Psyllidae) with Zebra Chip, a new potato disease in southwestern United States and Mexico. Journal of Economic Entomology 100(3): in press.<br /> <br /> Pappu, H.R., K.B. Druffel, J. Whitworth and M.J. Pavek. 2007. Incidence, transmission and molecular characterization of Potato virus S in selected potato cultivars. Phytopathology 97, In press (abstract).<br /> <br /> Salazar, L. F. 2006. Emerging and Re-emerging Potato Diseases in the Andes. Potato Research, 49: 43-47.<br /> <br /> Secor, GA, IM Lee, KD Bottner, VV Rivera-Varas, and NC Gudmestad. 2006. First report of a defect of processing potatoes in Texas and Nebraska associated with a new Phytoplasma. Plant Disease, 90:377.<br /> <br /> Tenorio, J, Y. Franco, C. Chuquillanqui, R. A. Owens and L. F. Salazar. 2006. Reaction of potato varieties to Potato mop-top virus infection in the Andes. Amer. J. of Potato Res., 83: 423-431.<br /> <br /> Thompson, AL, Novy, RG, Farnsworth, BL, Secor, GA, Gudmestad, NC, Sowokinos, JR, Holm, ET, Lorenzen, JH and Preston, DA. 2005. Dakota Pearl: An attractive, bright white-skinned cold chipping cultivar with tablestock potential. Am. J. Potato Res., 82:481-488.<br /> <br /> Thompson, AL, GA Secor, JH Lorenzen, BL Farnsworth, RG Novy, NC Gudmestad, ET Holm and DA Preston. 2006. Dakota Rose: A bright red tablestock potato cultivar that retains its skin color in storage. Am. J. Potato Res., 83:317-323.<br /> <br /> Thompson, AL, BL Farnsworth, GA Secor, NC Gudmestad, DA Preston and H Hatterman-Valenti. 2006. Dakota Jewel: An attractive, new, bright red-skinned, fresh market potato cultivar with improved storage characteristics. Am. J. Potato Res., 83:373-379.<br /> <br /> Srinivasan, R., J.M. Alvarez, S. Eigenbrode, and N. Bosque-Perez. 2006. Influence of hairy nightshade Solanum sarrachoides (Sendtner) and Potato leafroll virus (Luteoviridae: Polerovirus) on the preference of Myzus persicae (Sulzer) (Homoptera: Aphididae). Environmental Entomology. 35: 546-553.<br /> <br />

Impact Statements

1. Through identifying the components of the tuber necrotic complex and development of new diagnostic tools, this will allow heightened confidence in the diagnoses of viruses when high seed volumes move interstate for recertification and for commercial planting. Internal necrosis due to PVY cannot be used for planting commercial potatoes, the PVY survey and the Canadian quality assurance survey will provide information about the health status of seed.
2. The importance of managing the alternate hosts is strictly recommended to be a part of any devised virus management plan primarily by collaborating with state commodity commissions, agricultural departments and seed certification agencies. Recommendations for nightshade control have been developed and published.

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Report Information

Participants

Mathieu, Rolland (mathieu.rolland@rennes.inra.fa)-INRA (France); Srinivasan, Rajagobalbabu (babu@uidaho.edu) - University of Idaho; Corvantes, Felix (cerv1467@vandals.uidaho.edu) - University of Idaho; Alvarez, Juan Manuel (jalvarez@uidaho.edu)-University of Idaho; Barker, Ian (i.barker@cgiar.org)- CIP; McMorran, Jeff (jeff.mcmorran@oscs.crst.edu) - Oregon State University; Hane, Dan (dan.hane@oregonstate.edu) - Oregon State University; Pavek, Mark (mjpavek@wsu.edu)- Washington State University; Pasche, Julie (julie.pasche@ndsu.edu)-North Dakota State University; Unruh, Tom (thomas.unruh@ars.usda.gov)-USDA-ARS, Wapato, WA; Munyaneza, Joe (joseph.munyaneza@ars.usda.gov)- USDA-ARS, Wapato, WA; Karasev, Alex (akarasev@uidaho.edu) - University of Idaho; Gray, Stewart (smg3@cornell.edu)- ARS-Cornell; Bestes, Gerhard (gerhard.bester@fritolay.com)-Frito Lay; Salazar, Luis F. (lsalazar@agdia.com) -Agdia Inc.; Jensen, Andy (ajensen@potatoes.com)-Washington Potato Commission; Snell, Rue (rues@lamar.colostate.edu) - Colorado Potato Certification Service; Marquardt, Steven (skmarquardt@earthlink.net) -NE Potato Certification; Davidson, Robert (rddavid@ext.colostate.edu) - Colorado State University; Whitworth, Jonathan (jonathan.whitworth@ars.usda.gov)-ARS-USDA, Aberdeen, Idaho; Boze, Doug (dboze@idahocrop.com) - Idaho Crop Improvement Association; Bohach, Greg (gbohach@uidaho.edu) -University of Idaho; Guzman, Pablo (pguzman@ucdavis.edu)-CCIA; Nolte, Phillip (pnolte@vidaho.edu) - University of Idaho; Crosslin, Jim (jim.crosslin@ars.usda.gov) - USDA-ARS

Brief Summary of Minutes

WERA089 minutes - March 12-13 2008. San Antonio, TX

Chair Jim Crosslin opened the meeting by welcoming all attendees.

Introductions were made.

Administrative Advisor Greg Bohach made a few comments about the FY09 budget, we now know there will be no FY09 budget signed by the President and we will be on a Continuing Resolution until the next administration goes to D.C. The new Farm Bill and its provision for big new money for Specialty Crops (which includes potatoes) was discussed. Greg also mentioned a new program was established by State Exp. Station Directors; an Excellence Award for Multistate Projects. Greg and Jim Crosslin did submit a nomination packet for this award. All participants should formally register in NIMSS.

State Seed Certification Reports Followed:

Pablo Guzman described a new on-line application system that growers use to register fields for inspection and certification. The program is on the California Crop Improvement website and will be available for purchase at some point in the future. If interested contact the Director of CA Crop Improvement. Pablo provided a demonstration of the program which is password protected (Pablo would not share his password so we could not play with the system). Growers supply information on the crop, including variety, generation, seed origin, winter test results, other testing data if available, field information (location, history, date planted). The grower also provides a copy of the Certification Tag. Inspectors carry a laptop with wireless capability to the field and can upload data on site. A most interesting benefit, beyond ease of record keeping, was to provide spatial and temporal information on all fields so that maps can be easily generated showing the geographic distribution of disease and pest problems, crop locations, etc.

Jeff McMorran (OR) had a normal season overall in 2007. PVY symptoms were more mild, especially noticeable in Ranger. Some anecdotal evidence that milder symptoms were attributable to the recombinant stain of PVY (PVYN:O or PVYN-Wi as the European's like to call it). Mild symptoms were also noticed in the greenhouse winter trials. Commented that symptoms were more variable in the field than greenhouse.

Rob Davidson commented that over the past decade symptoms overall are more mild in the field. There was no major rebuttal to this comment.

Andy Jensen did not provide a WA state report, but did offer the comment that commercial growers were applying for exemptions from seed certification law that currently requires all seed entering the state be certified. Seed from within the state can be exempted from certification requirements.

Greg Boze reported that the Idaho growers had voted to assay all winter test material using ELISA. The growout was done in Southern CA (Central Valley). There was a slight decrease in incidence and rejected lots in 2007 compared to 2006, but he also commented that 2006 was an odd year. The winter test was not set up to allow a comparison of ELISA and visual symptom comparisons. Anecdotally, there was an increase in mild symptoms observed in the field, and much of this was not related to symptoms within the typical latent varieties-similar to the comment by Jeff McMorran. There were no hard numbers on the cost of ELISA testing vs traditional visual assessment of the winter test. Increase costs included sampling, shipping samples to the lab and lab testing. Greg still felt this was cheaper than doing the winter test in a greenhouse. Using 5 leaves per sample for a 400 tuber sample per lot as a standard he tossed out the cost estimates of ~$260 for greenhouse testing of the material vs ~$75 for field testing. PLRV incidence was on the rise and R. Norkota was the cultivar of choice for rejected lots.

A brief discussion ensued regarding the origins of the 400 tuber/lot sample. Phil Nolte indicated that Mike Sun et al. published a paper about this in the Am Pot Journal. SAMPLE-SIZE DETERMINATION FOR SEED POTATO CERTIFICATION
Author(s): LUND RE, SUN MKC, AMERICAN POTATO JOURNAL 62: 347-353 1985.
Tom Unruh indicated the number of samples is less important than how the samples are collected.

Rob Davidson indicated that Colorado had a typical year. 6K acres of R. Norkota did not pass inspection; 50% of these acres were decertified on the basis of the summer inspections and another 30-40% in the PHT. R. Norkota acreage is down in CO this year, and CO farmers are growing another 150 varieties that have few virus problems. Growers are beginning to admit to seeing yield loss due to virus.

Gerhard Bestes commented that some Atlantic lots out of CO had some PVY issues this year.

Rob also mentioned that CO is working on a Seed Law that will require all potatoes moving into the state be winter tested and certified. Also in-state material will need to meet standards in order to be replanted. Currently any in-state lot can be replanted.

Steve Marquardt reported that NE had no rejections last summer and only a handful in the PHT, less than last year. PVY was in R. Norkota. The winter test sample rate in NE is 500 tubers/40 acres. A NE seed law was passed early in March; imported seed must be tested and certified to meet NE tolerance limits (0.5%). NE also tried to conduct winter tests in Puerto Rico this year, the inspections were decidedly more festive than in southern Florida.

A series of research updates were provided by the following: Joe Munyaneza, Luis Salazar, Jim Crosslin, Ian Barker, Mathieu Rolland, Babu Srinivansan, Felix Cervantes, Jonathan Whitworth, Alex Karasev, Stewart Gray, Phil Nolte, and Julie Pasche.

There was a discussion on revisions to the Necrotic Virus Management Plan based on the information that Stewart Gray had sent out to participants prior to the meeting. There was strong support for the management of PVY strains rather than just managing PVY. This was based on the information from the 3 yr survey that strains are not distributed uniformly around the US and some states would like to keep the necrotic strains out if possible. Since no single test will identify all PVY strain or variant groups each state will have to identify what test they want to be conducted to determine strain/variant identification. Growers will be given the option of asking for more detailed information than just PVY levels, but they will have to have information on the various attributes and shortcomings of the various tests they may request. Perhaps some of this information can be provided in the Management Plan appendices. Discussions on tolerance limits and mandatory PHT did not identify consensus proposals although most agreed that PHT were necessary for recertification and for lots shipped out of state. Also tolerance limits should be defined and are defined for seed shipped between states. The issues are how the PVY incidence is determined and what the appropriate levels are for seed and ware potatoes. The NPC has developed a group of people that represents all aspects of the industry, seed certification and scientific advisors to develop and agree upon a strawman proposal that can be presented to the entire US industry. Once the US industry has agreed upon revisions to the plan then discussions will begin with Canada.

Jeff McMorran was elected Secretary

The rest of the meeting was devoted to identifying key impacts for NIMSS reporting.

Next meeting - Back in San Antonio? Send suggestions to Steve Marquardt

Meeting adjourned.

Accomplishments

Joe Munyaneza discussed the latest on Zebra Chip and its association with potato psyllids. Some symptoms of ZC are similar to Purple Top, but no phytoplasmas have been associated with ZC. The causal agent of ZC is still unknown, it is graft transmissible and ZC distribution is similar to potato psyllid distribution. When psyllids collected from infected fields or psyllids from a lab colony that were reared on ZC infected plants were introduced into field cages with uninfected potato, those plants did become infected. Joe is continuing cage studies with additional populations of psyllids. Joe commented that insecticides have some promise to reduce psyllid populations and ZC incidence, but application technologies are important since the psyllids reside on the undersides of leaves and are not effectively exposed to insecticide sprayed on the tops of plants. <br /> <br /> Luis Salazar commented that there is a disease in Bolivia called Saq'O that has similar symptoms to ZC and tubers harvested from these plants do not taste good. Also there is a new disease in California tomatoes that has been associated with psyllids might these diseases have a common or similar cause?<br /> <br /> Jim Crosslin commented on a series of grafting experiments he has done with ZC-infected plants. He is currently on the 10th graft transmission. The plants do not survive well, all tubers show symptoms. These tubers do not usually sprout and the few that do (~2-3%) produce healthy plants. It was generally thought that seed transmission was of little consequence. <br /> <br /> Ian Barker, CIP, Peru discussed emerging potato viruses. Potato yellow vein virus (PYVV) is spreading quickly through the Andes. It is a crinivirus transmitted by the common greenhouse whitefly in a semi-persistent manner. Believed to have originated in Ecuador, it is now in Peru and Venezuela. It has been responsible for yield losses up to 50% and it is also being spread in seed stocks. The vector, Trialeurodes vaporariorum, is increasing in geographic range and also in elevation. CIP is conducting a GIS spatial study to correlate vector, virus and environment (esp. rainfall and temp) to begin to develop predictive models of where the virus and vector are likely to spread together in SA and elsewhere in the world. Currently the disease is moving south at ~ 100km per year and there is concern the disease will move into the main potato production areas in Peru, Bolivia and Chile. Ian also mentioned SB29, an uncharacterized 29 nm diameter spherical virus that may be associated with psyllids and that appeared about the same time as ZC. <br /> <br /> Mathieu Rolland, a PhD student with Emmanuel Jacquot, INRA, Rennes, France was visiting Juan Manuel Alvarez's lab and gave a presentation on his investigations on the relationship of the PVY tobacco vein necrosis phenotype and sequences within the HC-Pro viral protein. Two amino acids were previously identified as being important in the tobacco vein necrosis phenotype <br /> (Tribodet, et al. 2005. J Gen Virol 86:2101), Mathieu was investigating the fitness of various viruses that contained different combinations of these amino acids in a PVYN background in single and mixed infections. To make a long story short, there is a fitness advantage for the necrotic background, but this is somewhat host dependent. This work should be published shortly. More info at http://www.apsnet.org/meetings/2007/abstracts/a07ma618.htm.<br /> <br /> Babu Srinivansan reported on his studies of Potato Aphid and Hairy Nightshade interactions. HNS is a reservoir of both PVY and the PA. PA has a preference for HNS over potato and this was true for multiple clones of the aphid collected from various field sites. PA transmitted PVYO and PVYNTN more efficiently from HNS than potato. A comparison of PA and Myzus persicae revealed that PA is more active, probes more, produces more alates than Mp. Also PA lives longer and has a high fecundity than Mp on HNS. There is no evidence that PVY is seed transmitted in HNS, but some HNS will overwinter. <br /> <br /> Felix Cervantes reported on investigations on the influence of HNS as a PVY inoculum source. HNS and PA were the best combination for efficient transmission of PVY. To determine why necrotic strains of PVY are detected more frequently he was investigating the differences in virus titer among various PVY strains in various potato cultivars (Yukon Gold, Ranger Russett, and 6LS). There were considerable differences in titer among cultivars and strains and these did influence the transmission efficiency of the viruses. See also http://www.apsnet.org/meetings/2008/abstracts/s08ma48.htm<br /> <br /> Jonathan Whitworth reported on two isolates of PVYO collected in Idaho that are capable of causing PTNRD in multiple cultivars including Atlantic, Cal White, Yukon Gold, Yukon Gem and Chipewa. Both of these isolates have been sequenced and both are most similar to isolates within the PVYO strain. Also both are identified as PVYO by the Lorenzen multiplex RT-PCR assay and by serology. <br /> Ian Barker commented that PTNRD expression is environmentally sensitive. In Europe the more North and West you move the more cultivars that express PTNRD.<br /> <br /> Alex Karasev reported on the 2007 PVY outbreak in Idaho commercial potato fields. A number of Russet Burbank tubers were collected that showed a high degree of internal necrosis. Many of these tubers tested positive for PVYNTN, one sample contained PVYN+O. A comparison of ELISA and Multiplex RT-PCR results indicated that 3-5% of the PVY isolates were not detected by the Multiplex assay suggesting significant sequence differences in the regions of multiple recombination junctions. When these isolates were inoculated to tobacco, symptoms did develop and virus could be detected using the Multiplex assay. It is unclear if there was a mixture of isolates in the potato, the predominant one that does not infect or do not multiple well in tobacco or if something else prevented amplification from potato tissue extracts. <br /> <br /> Stewart Gray provided an update of the PVY survey in the seed potato crop. The numbers of PVY positive tubers increased in 2006 (~8%) relative to 2004-2005 (~3%) and the number of PVYN serotypes also increased (~13%) relative to past years (~5%). Based on serological, tobacco bioassay and molecular data the relative proportions of PVY strains remained consistent overall (60% PVYO, 25% PVYN:O, 10% PVYO5, 5%PVYNTN). Just under 40% of the lots tested had detectible levels of PVY. There are also a number of isolates detected in small numbers that do not fit neatly into any of the currently define strain groups. None of the diagnostic tests are able to distinguish all of the PVY variants that are present in the US PVY population. Stewart also reported on research on the PVYO5 isolates. Their ability to be detected by the PVYN-specific antibody is due to a single amino acid change in the coat protein. There is no other indication that this isolate is different that typical PVYO isolates in virulence or pathogenic properties. <br /> <br /> Phil Nolte reported on experiments to investigate yield impacts of PVA. Work done in Hermiston and Parma using Russet Norkotah and Russet Burbank, started with various levels of initial inoculum by mixing healthy and infected tubers at the time of planting. Disease incidence was measured throughout the season and yield data was collected following harvest. In Russet Burbank a 10% virus incidence translated into a 8cwt/acre yield reduction. There was no significant effect on R. Norkotah.<br /> <br /> Julie Pasche reported on recent finds of TRV and PMTV in the upper Midwest. TRV was isolated from R. Burbank and Umatilla tubers grown in WI and MN. Typical necrotic arc symptoms were observed. RT-PCR analysis using RNA1 primers revealed that the virus in R. Burbank tubers was similar to described isolates, but the virus in Umatilla was different. Both viruses are mechanically transmissible to tobacco and are detected by TRV antiserum. Also both viruses are transmitted to tubers and infected tubers give rise to infected plants, albeit the Umatilla isolate is slightly less efficiently transmitted to progeny tubers than the R. Burbank isolates. PMTV was identified in one ND field and the virus has now been confirmed from 7 states. Ian Barker commented that in the UK symptoms of TRV and PMTV will vary from necrotic spots, rings and arcs and can be internal and external on tubers. Cannot distinguish these viruses by symptoms and tuber transmission is higher than reported. Also many varieties are asymptomatic.

Publications

Kaplan, I. B., Lee, L., Ripoll, D. R., Palukaitis, P., Gildow, F. E., and Gray, S. M. 2007. Point mutations in the potato leafroll virus major capsid protein alter virion stability and aphid transmission. J. Gen. Virol. 88:1821-1830.<br /> <br /> Singh, R.P., Valkonen, J. P. T., Gray, S. M., Boonham, N., Jones, R. A. C., Kerlan, C. and Schubert, J. 2008. The naming of Potato virus Y strains infecting potato. Arch. Virol. 153(1): 1-13.<br /> <br /> Gudmestad, N.C., I. Mallik, J.S. Pasche, and J.M. Crosslin. 2008. First report of tobacco rattle virus causing corky ringspot in potatoes in Minnesota and Wisconsin. Plant Dis. (in press).<br /> <br /> Kirk, W.W., S.L. Gieck, J.M. Crosslin, and P.B. Hamm. 2008. First report of corky ringspot caused by Tobacco rattle virus on potatoes (Solanum tuberosum) in Michigan. Plant Dis. 92:485.<br /> <br /> Boydston, R.A., H. Mojtahedi, J.M. Crosslin, C.R. Brown, and T. Anderson. 2008. Effect of hairy nightshade (Solanum sarrachoides) presence on potato nematodes, diseases, and insect pests. Weed Science 56:151-154.<br /> <br /> Mojtahedi, H., R.A. Boydston, J.M. Crosslin, C.R. Brown, E. Riga, T.L. Anderson, and D. Spellman. 2007. Establishing a corky ringspot disease plot for research purposes. J. Nematology 39:313-316.<br /> <br /> Crosslin, J.M., P.B. Hamm, K.S. Pike, T.M. Mowry, P. Nolte, and H. Mojtahedi. 2007. Managing diseases caused by viruses, viroids, and phytoplasmas. Pages 161-169 in: Potato Health Management, 2nd edition. D.A. Johnson, editor. APS Press.<br /> <br /> J. Lorenzen, P. Nolte, D. Martin, J.S. Pasche and N.C. Gudmestad. 2008. NE-11 represents a new strain variant class of Potato virus Y<br /> Arch Virol. 153:517-525.<br /> <br /> N.C. Gudmestad, I. Mallik, J.S. Pasche and J.M. Crosslin. 2008. First Report of Tobacco rattle virus causing Corky Ring Spot in Potatoes Grown in Minnesota and Wisconsin. Plant Dis. 92: (in press).<br /> <br /> Munyaneza, J.E., J.M. Crosslin, and I.-M. Lee. 2007. Phytoplasma diseases and insect vectors in potatoes of the Pacific Northwest of the United States. Bulletin of Insectology 60:181-182.<br /> <br /> Munyaneza, J.E., J.M. Crosslin, and J.E. Upton. 2007. Association of Bactericera cockerelli (Homoptera: Psyllidae) with zebra chip, a new potato disease in southwestern United States and Mexico. Journal of Economic Entomology 100:656-663.<br /> <br /> Munyaneza, J.E., J.A. Goolsby, J.M. Crosslin, and J.E. Upton. 2007. Further evidence that zebra chip potato disease in the lower Rio Grande Valley of Texas is associated with Bactericera cockerelli. Subtropical Plant Science 59:30-37.<br /> <br /> Munyaneza, J.E., A.S. Jensen, P.B. Hamm, and J.E. Upton. 2008. Seasonal occurrence and abundance of beet leafhopper in the potato growing region of Washington and Oregon Columbia Basin and Yakima Valley. American Journal of Potato Research 85:77-84.<br /> <br /> Goolsby, J.A., B. Bextine, J.E. Munyaneza, M. Sétamou, J. Adamczyk, and G. Bester. 2007. Seasonal abundance of sharpshooters, leafhoppers, and psyllids associated with potatoes affected by zebra chip disorder. Subtropical Plant Science 59:15-23.<br /> <br /> Goolsby, J.A., J. Adamczyk, B. Bextine, D. Lin, J.E. Munyaneza, and G. Bester. 2008. Development of an IPM program for management of the potato psyllid to reduce incidence of zebra chip disorder in potatoes. Subtropical Plant Science (in press). <br /> <br /> Srinivasan, R., and J.M. Alvarez, 2008. Hairy nightshade as a potential Potato leafroll virus (Luteoviridae: Polerovirus) inoculum source in <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Pacific Northwest potato ecosystems. Phytopathology. (in press). <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><br /> <br /> Srinivasan, R., J.M. Alvarez, N. Bosque-Perez, S. Eigenbrode, and.R. Novy. 2008. Effect of an alternate weed host, hairy nightshade, Solanum sarrachoides (Sendtner), on the biology of the two most important Potato leafroll virus (Luteoviridae: Polerovirus) vectors, Myzus persicae (Sulzer) and Macrosiphum euphorbiae (Thomas) (Aphididae: Homoptera). Environmental Entomology. 37: 592-600. :http//docserver.ingentaconnect.com/deliver/connect/esa/0046225x/v37n2/s36.pdf?expires=1214841950&id=0000&titleid=10265&checksum=75D55D321D778836A66535C16B25792E <?xml:namespace prefix = v ns = "urn:schemas-microsoft-com:vml" /><br /> <br /> Hoy, C.W., G. Boiteau, A. Alyokhin, G. Dively, and J.M. Alvarez. 2007. Managing insect and mite pests. In Potato Health Management D.A. Johnson ed. The American Phytopathological Society, St. Paul, MN. pp. 133-147.<br /> <br /> Srinivasan, R., and J.M. Alvarez, 2007. Effect of mixed-viral infections (Potato virus Y-Potato leafroll virus) on the biology and preference of vectors, Myzus persicae (Sulzer) and Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae). Journal of Economic Entomology. 100: 646-655. Available at: http://docserver.esa.catchword.org/deliver/cw/pdf/esa/freepdfs/00220493/v100n3s2.pdf<br /> <br /> Novy, R.G., Gillen, A.M., Whitworth, J.L. 2007. Characterization of the expression and inheritance of potato leafroll virus (PLRV) and Potato virus Y (PVY) resistance in three generations of germplasm derived from Solanum etuberosum. Theor Appl Genetics 114:1161-1172.<br /> <br /> Novy, R. G., Whitworth, J. L., Stark J. C., Love S. L., Corsini, D. L., Pavek, J. J., Vales, M. I., James, S. R., Hane, D. C., Shock, C. C., Charlton, B. A., Brown, C. R., Knowles, N. R., Pavek, M. J., Brandt, T. L., Olsen, N. 2008. Premier Russet: A Dual-Purpose, Potato Cultivar with Significant Resistance to Low Temperature Sweetening During Long-Term Storage. Am J Potato Res. 85 (in press).

Impact Statements

1. Aphid - PVY interactions: Demonstrated that there is a PVY strain - aphid vector species interaction and that transmission efficiency and transmission properties will differ among different strain-aphid combinations. Also demonstrated that Hairy Nightshade is a significant source of both virus and aphids. Management of nightshade is necessary for PVY control and appropriate recommendations will be a component of Regional Best Management Practices for PVY as they are developed.
2. Early response and prevention of emerging diseases: The WERA089 network responds to reports and findings of new viruses and vector transmitted diseases that are detected in potato fields. Activities include diagnosis and characterization of new or uncommon disease agents, identification of potential vectors, description of disease etiology and epidemiology, and development of appropriate management or control strategies and practices. Some of the recent diseases that WERA89 participants have been involved with are PVYNTN, PMTV, TRV, TSWV, AMV and ZC.

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Report Information

Participants

Abad, Jorge (Jorge.A.Abad@aphis.usda.gov) - USDA;
Alvarez, Juan Manuel (jalvarez@uidaho.edu) - University of Idaho;
Bohach, Greg (gbohach@uidaho.edu) - University of Idaho;
Boze, Doug (dboze@idahocrop.com) - Idaho Crop Improvement Association;
Crosslin, Jim (jim.crosslin@ars.usda.gov) - USDA-ARS;
David, Nick (nicholas.david@ndsu.edu)-Northern - Plains Potato Growers
Association;
Davidson, Robert (rddavid@ext.colostate.edu) - Colorado State University;
Eggers, Jorden (Jorden.Eggers@oregonstate.edu) - Oregon State University;
Franc, Gary (francg@uwyo.edu) - University of Wyoming;
Hall, Daren (Darren.Hall@ARS.USDA.GOV) - USDA;
Hamm, Phil (philip.b.hamm@oregonstate.edu) - Oregon State University;
Hane, Dan (dan.hane@oregonstate.edu) - Oregon State University;
Jensen, Andy (ajensen@potatoes.com) - Washington Potato Commission;
Karasev, Alex (akarasev@uidaho.edu) - University of Idaho;
Marquerdt, Steve (skmarquardt@earthlink.net) - North Dakota State Seed
Department;
McMorran, Jeff (jeff.mcmorran@oscs.orst.edu) - NE Potato Certification;
Munyaneza, Joe (joseph.munyaneza@ars.usda.gov) - USDA-ARS, Wapato, WA;
Nolte, Phillip (pnolte@vidaho.edu) - University of Idaho;
Pavek, Mark (mjpavek@wsu.edu) - Washington State University;
Sather, Kent (ksather@lamar.colostate.edu) - Colorado State University;
Siemsen, Susie (uplss@montana.edu) - Montana State University;
Thornton, Mike (miket@uidaho.edu) - University of Idaho;
Whitworth, Jonathan (jonathan.whitworth@ars.usda.gov) - ARS-USDA, Aberdeen, ID;
Zidack, Nina (nzidack@montana.edu) - Montana State University;

Brief Summary of Minutes

1) Call to Order-8:10 AM. Jeff M. passed around a printout of the roster, noting that the contact for several of those listed was out-of-date. Roster at: http://nimss.umd.edu/homepages/member.cfm?trackID=7516. Members should check & update this information.

2) Introductions

3) Approval of Agenda-No formal additions.

4) Correction/Approval of 2008 Minutes-one correction, for Idaho Report, Doug Boze should replace Greg Boze. Approved (I/II - Dan Hane/Doug Boze).

5) Report of the Western Association of Ag Experiment Station Directors (WAAESD) Administrative Advisor (Dr. Greg Bohach)- Mid-term Impact Statement will need to be prepared. This year is of special significance because it is a WAAESD review year. A fairly routine procedure, but of importance because it ensures the continued existence & funding for the project. Awards for the committee in 2008 included the regional WAAESD Outstanding Multidisciplinary Research Award. Certificates given to each member listed on the official roster (NIMSS System). Group did not get the national award but Greg encourages the group to apply again this year & feels the group stands a good chance to achieve this award. It includes national recognition, attendance at the national award meeting, & financial incentives to the group to fund guest speakers, etc. There is a very short turn around time to get this going.

6) Report of Seed Certification Personnel

Oregon-Jeff M. reported it was a relatively 'average' year for Oregon in terms of acreage & disease levels observed in field & winter grow-outs. Growers struggled to find a replacement for the Alberta seed sources they had planned to plant but were not available due to the nematode situation. Alberta seed has become an increasingly important source of clean seed for Oregon growers. Varieties grown continued to diversify away from Russet Norkotah & Russet Burbank into several of the PVMI & Colorado varieties, but no replacement for Shepody was available.

Idaho-Doug B. passed out a handout entitled 'Summary of Winter Test Plots 2002-2008'. Mosaic was stable in 2009 with a decrease in the number of ineligible lots. Rob Davidson felt the ID data showed that the seed programs were, by & large, working to keep virus down, though some failures still occur (as with R. Norkotah). Q:(Rob D.)Was the decrease in ineligible lots related to reduction in R. Norkotah lots? In Colorado they found that growers of R. Norkotah lots (and other latent varieties) had virus problems in all their varieties & when they quit growing R. Norkotah, PVY issues slowly went down, thus showing that these types of varieties should not be in the system! A:D. Boze)RN definitely a factor in management of mosaic in Idaho, PVY/PVA ELISA testing of all WGO lots is likely helping. No visual assessment is made of the lots, so any strains not giving +ELISA reaction would be missed. Q: Is PVA a problem? A:(Phil N.)Essentially all Mosaics were PVY not PVA, there are a few 'pockets' of PVA in Idaho but PVA does not seem to spread like PVY. Jonathan W. noted that basically 'you have to buy PVA' in the seed to get it.

A discussion on the differences between PVY & PVA followed. Data has shown that infection rates for PVY & PVA were 80% vs. 20% in similar field environments. Thus reduced plant-to-plant transmission may be involved. Steve M. pointed out that some PVA strains can be very virulent, as described in Slack's paper in the 1990s. It was noted that if PVA kills the host plants, that may actually reduce plant-to-plant spread in the field. The host range of PVA is also narrower than PVY, thus reducing the amount of over-wintering host plant sources of PVA. Jorge A. pointed out that the aphid vectors are also different for these two viruses as well as their preferred host plants.

Q:(Phil H.)Is Shepody was still considered a problem in regards to PVY management? A:yes. He noted cases in Oregon where Russet Burbank & Shepody fields with the same virus levels in the beginning of the season (and similar aphid exposure), were radically different at the end of the season, with mosaic levels in Shepody much greater than in RB. This has lead him to believe that the virus actually increases faster in Shepody than in RB plants.

Q:(Mike T.)Do you follow the ineligible lots to see how they perform relative to eligible lots then next season? A:(Doug B.)No. Mike noted that anything over 0.5% should not be planted as seed. Q:(Phil H.)Are there areas in Idaho with more mosaic problems than others? A:(Doug)Yes, there are seed control districts & most of the 'problem areas' are outside these control districts. Q:(Phil H.)Have there been any PLRV issues in the seed lots in general? A: No, little PLRV was observed by any of the Agency present in 2008.

Q:(Nina Z.) Was Idaho's ELISA program for summer lots? A: No just the WGO, where leaves from all 400 emerged plants (Idaho's standard lot size) are bulked by 5 & tested. In the summer program, all plants scored for mosaic are flagged, sampled, & tested for PVY & PVA also. Initially Idaho did a comparative test between visual & ELISA testing of the WGO and based on the results, switched over to an ELISA only system. Overall Idaho has been pleased with the ELISA only system for PVY/PVA in the WGO.

Q:(Steve M.)What is the basis of the 400-tuber standard sample size in Idaho? A:(Doug B/Phil N.)The switch was somewhat imposed as a cost saving measure but was also based on work done by RE Lund & Mike Sun in 1985 ('Sample size determination for seed potato certification' Am. Pot. J. (62) 347:353) that showed little benefit in determining the accuracy of the % virus in the lots above the 400 tuber level. Steve M. pointed out that this conclusion assumed a truly random sample, which may not be the case for very large acreage lots if only 400 tubers are taken. Larger WGO lot sizes may better represent the entire lot (i.e. be more 'random'). In Idaho, they felt the cost saving of the 400-tuber standard lots size outweighed the potential drawbacks of not having a larger sample size. The concept of A & B samples for the WGO as also discussed (A=primary sample, B=backup sample in case of challenges on the results of the A sample). Kent S. pointed out that this system has worked well in solving grower challenge issues in Colorado, & that in general the B sample results confirmed the results of the A samples.

Colorado-Kent S. presented slides showing the acreage change of several states from 1995 to 2008. Most were down (ND, WI, MI, ID) some were up (CO) some about the same (MT). Q:(Gary Franc)Does this downward trend means supply is down (short) or need is down; are adjustments needed? A:(Rob D.)Part of the reason acreage is down is that many of the 'poor growers' who produced rejected lots are no longer in the system, thus meaning that more of the acreages entered are accepted. (less 'lost lots'). In Colorado anyway, they have fewer growers & less acreage, but more 'serious/better growers'. An increase in seed yields over time has also helped offset acreage loss. Colorado, Nebraska, & Wisconsin are in the process of implementing a state seed law (i.e. requiring all potato acreage to be planted with certified seed). All other potato seed states have seed laws in place. Phil N. noted that Idaho has a seed law, but it is not well enforced, & some folks still 'get burned' planting uncertified seed. Although the initial seed laws were put in place to help control Bacterial Ring Rot, it was felt by the group that such 'certified seed only' requirements also help keep PVY under control (albeit to a lesser degree than BRR). Phil N. noted that no system is perfect but the primary issue is that 'what is sold needs to be controlled', not necessarily what is kept on the farm & not sold..

Kent also showed a slide on acres entered vs acres accepted 1975-2005. There was a steady increase in acres entered. Three periods of high rejections were noted: (1) late 1970 where PLRV rejections predominated; (2) early 1980 where Bacterial Ring Rot was a problem; (3) 2000-08 with rejections rising due to PVY. He also pointed out the years Russet Norkotah was introduced was not the year PVY issues stated, it took several years for the PVY inoculum to build up & cause general wide-spread problems. The BRR problem was caused when a commercial warehouse was used to store seed & exposed several seed lots to BRR, resulting in a very aggressive push by certification & the industry to control this disease in seed lots (many stars in the book). Development of good & fast test methods for this disease, implementation of the flush through system, & use of tissue culture, has created the overall control of BRR in Colorado (as else where). The move from many small farms to fewer & larger operations has also helped.

Q:(Jeff Mc)What are the Russet Norkotah acreages being replaced with? A:(Kent/Rob D.)Many of the new PVMI varieties (Canela Russet, Classic Russet, Blazer Russet). Any early variety with good grade out & that have PVY resistance (but showing good PVY symptom expression) are potentials. Kent was particularly impressed with Classic Russet noting a case where a late-planted, late-harvested lot (which made it prone to getting PVY) ended up with very little mosaic in the WGO. Jonathan W. noted that Classic Russet is the perfect variety for PVY control because it has good resistance & good symptom expression allowing PVY to be rogued when present. Dan H. noted that Shepody is still an issue in PVY management because, as of yet, there is no good replacement for this very early processor.

Colorado is still only a PVYo state, though PVYo5 strain (that gives a positive to PVYn antisera) is causing problems with shipments to Mexico(Alex talks about this more, see accompishments). PVYn may be present but is not at all widespread. Alex noted that any program that only uses monoclonals for PVY-ELISA detection could select for this problem. Q:(Phil H.)Are certification agencies routinely doing PVY strain surveys? A: No, because this PVY strain identification is not part of states standards, & most programs are based on visual mosaic (i.e. they only need to be sure the mosaic is viral caused, not which strain causes it). Above all, there is not yet available & affordable diagnostic test that differentiates all occurring strains.

Q:(Mike T.)Has the Late Blight quarantine in CO has worked to limit this disease in CO? A:Yes, it seems to have worked. There are a few incidences but no blowups. Organic growers in areas of commercial potato sprayed for LB have seen less LB in their tomato crops, which Rob Davidson felt was due to a reduction of LB spores in the area.

Montana-Nina Z. reported that her official year began in October, but she had spent part of the summer visiting growers in Montana. No PLRV was observed in 2008. The Winter Grow-out results pretty much mirrored the summer readings, with just a few downgrades or rejections. Russet Norkotah is still a problem for some growers in regards to PVY. Keeping levels below 2% can be challenging for these growers (no surprises). They do have one grower who has never had a +PVY in his Norkotah lots, he lives in an area with very severe winter weather, so this might help. Q: What is the tolerance for PVY in the Montana WGO. A: The WGO levels are for the grower's information only, they can advise the grower, but not reject lots based on the WGO level. They do have a 0.5% Mosaic limit for re-certification.

Nebraska-Steve M. reported this was a good year for Nebraska lots, with few rejected. Nothing new to report. They note that mosaic occurred in previously 'clean' seed lots while grown near wild plum & chokecherry trees that occurs in hedgerows.

Washington-Andy Jensen was present but had nothing to report.

North Dakota-(this was given by Nick David on Thursday)N. Dakota & Minn. had a very wet spring & summer, resulting in much of the crop not being harvested this year. WGO results of 373 lots from ND & MN showed 80% of lots entered were eligible for recertification, 60% had no detectable virus. ND has very few Russet Norkotah so PVY is not as big of an issue in this state as other areas. PMTV is present, but not a problem. MN has not had a major problem with TRV. It is in 4 regions of the state but low volume applications of Vydate 4 times in the early season 3 weeks apart are effective in controlling the nematode vector. Discussion on how the depth of penetration affects the efficacy of Oxamyl in control of stubby-root nematode followed. It was noted that the nematodes follow the roots, so if the previous crop was a deep-rooted crop like corn, the Oxamyl would only be effective if it reached fairly deep into the soil.

Othello & Hermiston Commercial Seed Lot Plots-Phil Hamm reported on strains studies done at the Othello & Hermiston Commercial Seed Lot Plots that showed most mosaic found were PVYo, though some PVYno, PVYn, & PVYntn was also present. Owners of these lots were notified. Incidence of PVYno was down. Alex pointed out that in France the reverse is true, that there was more PVYn than PVYo. Another report on the Othello Seed lot trials was given by Mark Pavek (see Accompishments).

A Series of research updates were provided by the following(see accomplishments): Phil Nolte, Alex Karasev, Jonathan Whitworth, Darrin Hall, Phillip Hamm, Mark Pavek, Juan Alvarez, & Steve Marquerdt.

Needed Research should include: 'Work on vectors & alternative host known to transmit/harbor PVY' & 'Improvement in practical detection methods for PVY & PVY strains'.

9) Additional Business
Greg Bohach addressed the group about (1) the need to prepare the report for this year; (2)the need to have the 2008 publications related to WERA089 of each participant included in the minutes (see publications); (3) Update individual member profile information on the NIMSS web site. (both the 'Appendix E: Participation' & 'Participants Directory') (http://nimss.umd.edu/homepages/home.cfm?trackID=7516).
Jeff had circulated a printout of the current 'Participants Directory' information on the NIMSS site so members could see who & what was posted. Q: Should the NVMP be included in the list of publications? A: Probably not, it would be listed under impacts. It is important that these are updated, & the Impact & Accomplishment of the group be documented, because this is the 5 year project review & it will either be extended or disbanded based on this review.

a) Impact & Accomplishment Statements - What is noted below refers to the items for the 'Submission Form for WAAESD Impact Statements' form that was handed out.

Impact Nugget: The research & extension work done by this dynamic multidisciplinary committee has resulted in the characterization of critical emerging virus & virus-like problems that are threatening to impact potato production, exports, & global competitiveness of the United States.

Issue: Stakeholders, consumers, & producers of the 4th ranked food crop in the US production & the most widely consumed vegetable. Specifically those benefited from the groups actions include: federal agencies, state & commodity commissions concerned with potato crops, Potato Association of America & the US Potato Board, potato grower associations, potato producers & consumers, potato marketing & trade groups.

What has the project done so far?: Facilitating collaboration & maintaining dialog in the use & development of an array of state-of-the-art techniques used to address the problems associated with potato viruses, including scoping surveys, vector management, serological techniques, symptom identification, grower education, & fostering conferences.

Impact Statements:
1. BLTVA: Role of psyllids in transmission of BLTVA & development of control strategies for the disease caused by this pathogen.
2. PVY Characterization: Identification of a new 1F5 antibody for accurate characterization of the 'O5' strain of PVY & refinement of the interactions between potato variety, PVY strains, & methods of inoculation.
3. Necrotic Virus Management Plan: Revised & updated, based on data obtained through the bi-lateral Scoping Survey work, thereby allowing trade between US & Canada to continue uninterrupted.
4. TRV/CRS work: Detection of the presence of TRV in states outside the Pacific Northwest, recognition of new symptoms, & recommending Vydate based control measures for this nematode-virus complex.

Research Needs for Future Impacts:
1. Survey of virus strains & work on how they impact management of viruses.
2. Descriptions of foliage & tuber symptom expression of various viruses & virus strains in the potato cultivars grown in the US.
3. Improvement to the detection & characterization tools used for new strains of virus, & the development of practical, applied, large scare, tests for potato plants & tubers.

b) Grant submissions-Greg went on to say the group neededs to rewrite the proposal for WERA089. It is due in 2010. Juan asked why it was important to get USDA approval for this group. A: States receive Hatch Act money, of which 25% must be used for activities like this group (i.e. to help defray travel expenses, etc.). In addition, having a recognized WERA title helps to 'legitimize' the group & makes it easier for those traveling on non-Hatch Act funds to get travel approvals for attending it's meetings, as well as receiving University recognition for their involvement.

Other Items: Greg asked if the group wanted to try for the 'Outstanding Multidisciplinary Resource Award' in 2010. Details & the criteria for this award are listed on the ESCOP web site: http://escop.ncsu.edu/. The answer was 'yes' & a committee made up of Phil N., Phil H., Rob D., Gary F., Alex K., & Steve M. was formed to move the process along. Greg also mentioned that the minutes for this meeting must be approved & posted within 60 days, & should include publication reference citations of group members for 2008. Lastly, Greg asked what to do with the plaque received for the regional 'Outstanding Multidisciplinary Resource Award' last year. A: It should be kept with the 2010 Chair (Stewart Grey). It will help remind him to organize the 2010 meeting!

Tuber testing for tuber necrosing viruses: Kent Sather asked the group about where they were sending samples (of tubers) to test for Necrotic Virus as mandated in the NVMP. He knew that Jim C. had been doing this but needed to back off the routine testing work. Currently Western Labs & Agdia are offering this service. Kent noted that they had had some unacceptable delays when they asked Western Labs to run this test (truck waiting at the border). Phil H. mentioned that they could run a limited number of these tests quickly if it was an emergency situation.

10) Election of Secretary
Joseph Munyanza was unanimously elected Secretary (I/II Gary F./Juan A.)

11) 2010 Meeting Location & Date - after several suggestions, consensus was that the 2010 meetings be held in Tucson. The same hotel would be fine (though not required, the Best Western across the street was suggested as another option). Juan suggested that the chair negotiate with the hotel to see if we can get the meeting room for free, or at a reduced rate, in 2010.

Appreciations: Juan wanted to give official appreciation to Greg B. for his efforts in nominating the group for the regional & national award in 2008. Thanks were also given to Steve M. for organizing this year's meeting.

USDA Commodity Based Reference Guide-Gary F. (for Richard Zinc who was not able to attend this year due to weather related issues) presented a request to the group to help with a new guide that was being put together to produce a series of fact sheets on new & exotic export pests that would help inspectors when/if they encounter what might be a new exotic pest. They are looking for experts who could provide good images, descriptive text, & be listed as resource people on the publications. Gary showed several slides that listed many of these pests/disease that included: Old World Bollworm, Black Maize Bettle, Silver Y Moth, Rice Cutworm, Andean Potato Tuber Moth, Potato Wart, Potato Smut, Common Rust, & 9 viruses including PVT, PVU, PVV, Tomato Spotted Wilt Virus, Tobacco Ring Spot Virus, Potato Deforming Virus, Tobacco Torrado Virus, Potato Yellowish Virus. Gary will email more on this to the project, including the complete & correct list.

12) Adjourn - Meeting Adjourned at 11:45 AM

Accomplishments

*Phil N.-Interactions between PVY & Rhizoctonia. He reported a study in ID during 2007-08 that suggests a link between the incidence of PVY & Rhizoctonia. Fields with high PVY also had high Rhizoc. Data compared PVY levels with yield produced, indicating a 1.5 cwt reduction for each 1% PVY. Fields of low mosaic vs high (>50%) had yields of 411 vs 300 cwt; with US#1 yields of 260 vs 160 cwt Most +PVY plants also had Rhizoc. Plants with & without PVY were dug & the roots were examined for Rhizoc; 81% of the Mosaic plants had Rhizoc while only 12% of the healthy plants had Rhizoc. Was yield reduction due to PVY or Rhizoc? Are PVY infected plants more susceptible to Rhizoc or are Rhizoc infected plants more susceptible to PVY?<br /> Q:Did the plants with PVY acquire Rhizoc the previous year & thus the effect was not purely seasonal? i.e. plants with PVY die down early, acquire Rhizoc, & it appears in year 2 A:Maybe, but the previous years field was out of potatoes 8 years so shouldn't have much Rhizoc. More RIGOROUS study may answer these questions. Jonathan W. noted that in his plots, PVY infected plants were more severely eaten by Colorado Potato Beetles than non-infected plants, whether this was because the beetles are attracted to higher sugar levels in the +PVY plants or if the feeding action reduced re-growth rates of the plants was not known. Rob D. noted that there are many cases in CO when a grower challenges a mosaic call, saying its 'just Rhizoctonia', but lab tests confirmed PVY presence. He also pointed out that, under CO conditions, the 1.5 cwt per 1% PVY rule does not hold true, fields with essentially 100% PVY were only yielding about 7-9% less than comparable clean fields, perhaps just a 'Colorado effect'. Phil N. said PVY & PVA vary in regards to being 'current season' or 'tuber perpetuated' with CS infection only reducing yield significantly if they occur early in the season.<br /> <br /> *Alex K.-PVYo5 in shipments to Mexico. Loads are being rejected at the border for PVYn. Results showed that it was PVYo5 which reacts + in the PVYn ELISA with 1F5 monoclonal Ab, the NAPPO required test for PVYn. Rules need to be changed to allow another antisera or PCR. The original 1F5 came from Peter Ellis & is a monoclonal. Extensive testing using indicator hosts, tuber inoculations, & isozyme analysis, has shown that PVYo5 is a strain of PVYo accounts & does not pose a risk to the Mexican potato industry. Only serology is different (based on a single nucleotide difference). Survey work has shown that PVYo5 is widely spread across the US, and 10-16% of the PVYo detections are PVYo5, perhaps as high as 25% in CO. Alex showed results indicating correct identification by different antisera suggesting NAPPO rules should be changed to allow this new protocol. <br /> <br /> *Jonathan W./Darrin H.-Tubers Symptoms of PVY in PNW Potato Varieties. Objectives were: (1) See how many PVY+ tubers could be expected with different strains of PVY; (2) See what tuber symptoms are expressed from strains (-ntn, -o, -no, & -n) on various potato varieties (Alturas, Blazer Russ, Premier Russ, Highland Russ, Russ Norkotah, Ranger Russ, Yukon Gold-current season infection). Procedure was: start with clean mini-tubers, inoculate young plants with a spray gun, & evaluate tubers for symptoms at harvest & after storage. Tuber symptoms were often mild at harvest & became more severe when stored. http://www.aphis.usda.gov/plant_health/plant_pest_info/potato/pvy_symptoms.shtml Different PVY strains caused differing symptoms in various varieties, i.e., PVYntn caused no tuber symptoms in A or PR, but other varieties were affected. (see the attachment under minutes for more details).<br /> <br /> *Jonathan W.-PVY Strain Survey Specialty Grant. Jonathan discussed a new Specialty Grant to monitor PVY strains in seed crops over time. He felt the most efficient way to accomplish this is to have certification agencies submit positive PVY samples in the WGO to him for PVY strain analysis. They don't want tubers/leaves, but feel there is enough virus left on a typical ELISA plate to conduct the analysis, thus the +samples could be circled, plates dried, & sent or samples could be dotted to Nitrocellulose, dried, & sent. To not bias the results, the +PVY samples should be from lots where the initial samples were taken randomly (like in ID), not just conformational samples taken from plants showing mosaic symptoms. They can't use federal funds for matching on this grant so an estimate of time spent by each agency would be used for 'payment in kind' on the grant. Results will be presented by variety. Industry input & direction is critical in obtaining this grant. Jonathan also discussed the need for a national isolation screen program that would compile 'PVY strain' x 'Potato Variety' information (i.e. leaves & tuber susceptibilities/symptom expression under field conditions). Two or three sites could be used. Wisconsin (Amy C.) has already expressed an interest in participating. He also showed promotional literature for 'Classic Russet' repeating an earlier statement that CR is the perfect variety for PVY management because it has good resistance & readily expresses symptoms when infected with PVY. http://www.pvmi.org/Storage/General/Classic Russet Flyer 1 09.pdf<br /> <br /> *Phillip H.-Screen House Study with PVY Isolates. He reported how various PVY strains react in various cultivars. Foliage & tuber symptoms were observed and they tested for PVX. The screen house environment was as close to field condition as they could get, with 20% shading which most experts said should not affect symptoms expression/virus behavior. Inoculation was via air spray gun on June 26th (same set-up as Jonathan W. used). ELISA testing was done July 9, Aug 1, & Aug 14. PVY strains: o(2), -ntn(2), -n:o(2). Cultivars: Yukon Gem, Yukon Gold, R. Norkotah, Blazer R., Ranger R., R. Burbank, Alturas, Premier R. Tubers were examined for external & internal symptoms. PCR was used to detect PVY strains on tubers. Plants were planted in 4 row blocks with netting around each block to prevent plants from touching. Phil summarized his data. In most cases, the PVY killed the plants by the end of the season. PVYo caused a variety of symptoms from distortion & vein burning in YGe, severe mosaic with no vein burn in BR, to very mild symptoms in YGo & RN. PVYntn gave very different symptom expression in the varieties inoculated, being very mild in YGe but more severe in RR & PR. Data on the % infection by strain & cultivar was shown, strain n:o was the highest, -ntn the lowest, but this varied in each cultivar. The amount of PVY infection by variety was also shown. Overall PR was the lowest, RN the highest. In A, PVYo infection was very low while PVYntn was very high, & one isolate of PVYno was high while the other was low. Yield effects of the virus were also shown & were not comparable to % infection levels, those plants with ntn had higher yields than those infected with PVYo, but this effect varied with variety. The two different PVYn:o strains behaved very differently in the various cultivars. Phil showed slides that compared yield effect on the time PVY gave +reactions in ELISA (the later the +reaction the less the yield effect). Phil N. noted that a longer growing season would likely have increased the differences observed between the strains. He also pointed out that PVY infection always results in a yield loss, but the magnitude depends on when the plant is infected. Tuber symptoms of PVY strains were also followed. Overall the healthy control & PVYo strain had no tuber symptoms. The -ntn strain showed tuber symptoms in most cultivars. Tuber symptoms with the -n:o strain varied between the two different n:o isolates used. Symptoms included arcs, spots, zones, circles, bruise-like areas, & black spots. PCR is the only fast/accurate test available. One important conclusion from the foliage & tuber part was that different strains of PVY react differently in various cultivars. Phil's conclusions: (1) Differing strains effect each cultivar differently & infection level is not proportional to symptom expression; (2) Resistance to PVYo does not mean resistance to other PVY strains; (3) PVY decreased yield, for all strains, in all cultivars, but the magnitude of this effect varied with cultivar & PVY strain; (4) Internal tuber symptoms varied with PVY strain & potato cultivar (See the attachment under minutes for more details).<br /> <br /> *Mark Paveck-Othello Seed Lot Trials. Data was by variety & included: # of lots by state/province for years 2001-08, & data for lots in the severe category (>10 plants per lot) for PLRV, Mosaic, & Blackleg. The # of total lots have been increasing each year. The highest mosaic levels were observed in RN & Shepody. The highest Blackleg incidence was observed in PR Very little PLRV was observed. Some states had over 40% of lots with severe mosaic, Montana had very few, & Canada none. Mosaic levels overall continued to rise from 2001-08. In 2008, 15% of the lots had severe levels of Mosaic, 4% had severe Blackleg levels, & only 3% had PLRV.<br /> <br /> *Juan Alvarez-Several Insect Vector Studies.<br /> <br /> (1) Characterization of the PVY virus receptors in Aphids. PVY has been shown to attach specifically to receptors inside the 5 um of the stylet tip. Previously it was believed that 20 microns were involved or that the virus simply contaminated the stylet. A micrograph showing this attachment site was shown.<br /> <br /> (2) Looking into the efficacy of insecticides for reducing transmission of PVY. Most insecticides reduce aphid populations, but few reduce virus transmission. Can virus transmission be prevented with insecticides? Rows of potatoes were exposed to viruliforious aphids, sprayed with various insecticides a few days later, then tested by ELISA at several subsequent dates to find out how much virus transmission took place. Insecticides: Provado, Monitor, Movento, Platinum, & Fulfill, alone & in various combinations. They could only use PVYo. Green Peach & Potato Aphids were counted each week after introduction to the plots to compare control. Two applications of insecticides, the 1st at 1 day & the 2nd at 2 weeks after aphid introduction. In summary, Vydate & mineral oil worked poorly in the reduction of virus spread. Some of the others worked fairly well. Mineral oil might have worked better if >2 applications had been used, however phytotoxicity & application cost may have become a problem (in Europe they use at least 6 per season & often combine it with a pyrethroid). The major confounding problem encountered with the treatments was due to the aphids not colonizing the plant block and/or aphids coming off other blocks.<br /> <br /> (3) The role of Hairy Nightshade in the spread of PLRV & PVY. PLRV infected potato were planted in treatment blocks of: clean HN & PLRV infected HN. The spread in plots of PLRV-HN almost equated the plots with only HN, & both were much greater than the spread in plots without HN or with PLRV infected potato plants. They did the same type of experiment with PVY & HN and found similar results i.e. that HN was a major factor in the spread of PVY within the plots, pointing out the critical nature of controlling HN in potato fields to help control both PLRV & PVY spread. They also studied the efficacy of different aphids in virus transmission on these plots including Green Peach Aphid, Potato Aphid, & Bird Cherry Oat Aphid. They concentrated on the BCOA because aphid traps had shown that at times of the year when they were only trapping 5 GPA & PA, they were trapping 3,000 BCOA, & 300 RGA (tall tube traps that represent a 50 mile radius). Even though transmission efficacy may be lower in BCOA (compared with GPA & PA) it may play a more significant role in virus transmission. In these studies they were finding the GP had 71% transmission efficiency, PA had 29%, & BCOA had 11.5%. Sheer numbers of BCOA thus would outweigh lower transmission efficiencies. For all aphid types, PVY transmission was higher in HN plots than plots without HN. PA showed the highest transmission, perhaps due to greater mobility within the plot (the GPA tended to stay on the original leaves). Juan said this experiment showed him that if you want to find PVY in a potato field, look at the HN. The role of HN in PVY spread should not be underestimated. The seed is viable in the soil for a long time.<br /> <br /> Aphids can move & transmit virus on up to 4 HN plants before loosing the virus & maintain viruliferous for up to 6 hours after feeding. Winged forms of aphids have the potential to really spread the virus especially if HN is in the picture. They are currently looking into effects of HN volatiles in transmission of PVY. Juan noted that the differences of transmission efficiency indicates there are biological effects on virus-stylet interactions that effect attachment-detachment i.e. it's not just a matter of release upon probing/feeding. It was pointed out that some years you find high levels of spread with low levels of aphids, indicating that aphids must be able to spread to many plants after they acquire the virus. On the other hand, some years there are a lot of aphids present & little spread of the virus, indicating a complex biological interaction far from the original 'dirty needle' transmission theory. Q:(Nina Z.)Could individial aphids be monitored as a means of predicting potential spread. A:No, there can be a lot of un-attached viruses on the stylet, but only the attached virus seems to be important in the transmission. Andy J. pointed out that the same is not true for PLRV where there is a direct correlation between level of virus in the aphid & transmission rates. Juan noted there is also a host effect. When an aphid lands on a plant it doesn't like (and thus only feeds a short while), there is often greater transmission than on plants it likes. It has been demonstrated that the longer an aphid feeds on an infected plant the less likely it is to acquire the virus. Aphids feeding for 1 minute on an infected plant were more likely to transmit the virus to a healthy plant than those that had fed for 2 minutes. Using an insecticide will not reduce the ability of aphids to acquire a virus from infected plants, but will reduce the number of aphids that build up reducing subsequent secondary infield spread. <br /> <br /> (4)Interactions of Potato Variety Virus Strain on transmission efficiency. A study in which the % infection rates & concentration of virus in the plant was compared between aphid & mechanical transmission. PVY strains: -o,-n:o, & -ntn. Potato varieties: Ranger R., Yukon Gold, Premier R. Effects varied with variety. PR-aphids were unable to transmit PVYo, there was a low transmission using mechanical means. YG-both aphids & mechanical means successfully transmitted the virus (though at different efficiencies, 68% vs 87%). The titer of the virus was much greater with mechanical means. PR-aphids had a low level of infection with PVYn:o, when it occurred there was a very high titer. A discussion of the transmission of these strains followed, including the significance of the differences that transmission & plant titer may have on virus spread. The first is a measure of 'at the time' effect, the latter is an 'after the event' phenomena. Juan emphasized that in regards to effects of this virus on potato varieties (transmission rates & symptom expression) aphid transmission does not equal mechanical transmission.<br /> <br /> *Revisions were made to the Necrotic Virus Management Plan. Steve Marquerdt lead the discussion on two aspects of the NVMP. (The complete revised text is in the Attachment under minutes)(1) 'Strawman' proposal to revise the current PVY management plan. (2) Revision of the 'Canada/US-Management Plan for Potato Viruses that Cause Tuber Necrosis'.<br /> <br /> *Alex: They have found a new strain of PVY in ID that typed-out as PVYntn that is not necrotic in tobacco indicator hosts. The difference between this PVY & their 'type strain' was a single nucleotide substitution. This shows just how confusing & complex characterizing the PVY strains can become. <br /> Rob D: Why 'all of a sudden' are there so many 'new' strains of PVY? <br /> Alex: In the last 10 years or so there have been some shifts in potato varieties grown, resulting in a large change in selection pressures. The increased production of RN & Shepody have raised the pool of inoculum so high that these strains have been able to increase without initial notice. There have been varieties introduced with only partial resistance to PVY; these have increased the selection pressure on PVY to develop new strains (a situation similar to using sub-lethal does of insecticides & insect resistance). It isnt known for sure if the new strains were already here & are just increasing due to selection pressures, or if they are truly new recombinants. Jonathan mentioned he has pictures from the 1940s of the variety 'Chippewa' with what look like PVY induced ring spots. Phil H. thought that in the past some PVY infected tubers might have been misdiagnosed (i.e. one slide showing known PVY tuber symptoms looked like it could have been caused by Fusarium). Alex pointed out that Potyviruses are the most successful virus type in the world & show an amazing ability to evolve into new successful strains.<br /> <br /> *PLRV is essentially 'out but not quite gone'. Few states are finding PLRV anymore in seed lots. Phil N. pointed out that as PLRV has decreased PVY has increased, could there be a link? Perhaps the increased use of Admire in potato fields is associated, but surely other factors are involved. Is Admire widely used in other crops? Unknown, maybe canola. Alex noted that the new strains of PVY that were emerging in N. America are not new. They have been in Europe for a long time & are just now undergoing selection here. It may be inevitable that we are seeing an increase due to various selection factors. <br /> <br /> *PMTV-Phil Hamm has been doing work on this virus-fungus complex (with Powdery Scab). PMTV in tubers have been reported from Quebec, parts of the US, & is wide spread in Europe. Symptoms of PMTV in tubers were shown (distinct necrotic arcs). Phil went on to describe the original survey by Canadian scientists that was made on symptomless US processing potatoes (chips) & one seed sample coming into Canada. In this original study PMTV was found in seed from 9 states & in 1 to 33 lots per individual state. Due to the dire political ramifications of these results (i.e. quarantine-wise), this study led to the alarm about PMTV in US seed sources, resulting in PMTV survey of ALL US seed sources. In the US survey, the only +PMTV finds were in Maine. For more information contact Phil.<br /> <br /> Phil presented slides showing results of a study soil from Powdery Scab where infested fields were tested for PMTV via PCR. The objective of his study was to test Powdery Scab infested soils for PMTV from as many potato-producing areas as possible. This was done by planting tobacco in the soil in the GH, looking for symptoms, & then testing the resulting symptomatic plants for PMTV. Q:(Phil N.)Europe has a problem with PMTV so why the difference? A: Probably climatic differences moderating symptom expression, & possibly variety related. Juan also pointed out that there are different strains of Powdery Scab, some transmit PMTV well & others do not. There may be different PS strains in Europe than the US. Q:(Jeff)Is it possible that some PMTV plants are mistakenly being scored as Alfalfa Mosaic Virus? A:Not likely, PMTV is rather distinct & generally occurs at the bottom of the plant whereas AMV is generally at the top. PMTV does not always occur on stunted plants, as might be inferred by the name of the Virus. Phil said he needs more soil samples in 2009 to continue this work. Samples should be about ½ gal & taken from fields known to have a PS history. He will be contacting everyone.<br /> <br /> *TRV-Jim C. showed slides showing tuber symptoms of Corky Ring Spot disease which is caused by TRV & vectored by Stubby Root Nematodes. These are found in Potato Progress Vol VIII #1 http://www.potatoes.com/PotatoProgress.cfm in the Research Library section, contact Andy J. for a password. He noted that there are not many requests for TRV testing from his lab, though he suspects that is because the growers know what TRV/CRS looks like & do not need lab confirmation. It certainly is still around in some fields. Q:(Rob D.)Is there any value in fumigating a field as protection against CRS if only low numbers of stubby root nematodes are found? A:(Phil H.)Yes. <br /> <br /> Phil H. showed a slide of deformed sprout symptoms caused by TRV. Initially they thought it was a herbicide problem, as there were no foliar symptoms of TRV in the fields. He then showed aerial photos from 3 fields in Columbia Basin that demonstrated how devastating this nematode/virus can be, causing poor emergence & large dead areas that can sometimes affect 30% of the field. Q:(Rob. D.)How long does it take from the initial infestation of a field before a grower might observe these type of dead areas. A:(Jim C.)The nematode moves very slowly under normal conditions, so it may easily take 10 years for major field damage to be observed. However, it depends on the rotational crops. Stubby Root N. increases very quickly in corn, so if corn is in the rotation, damage may be observed sooner/more severely. Jim C. noted that often plants with TRV also have Rhizoctonia (or look similar) & he suspects that in the initial stages of a build-up, the TRV infected plants are simply called Rhizoc infections. Q:(Mike T.)Are the poor areas associated with soil type i.e. like sandy ridges? A:(Rob D.)Perhaps. CRS pockets are often associated with sandy ridges in CO.<br /> <br /> The common denominator of all three fields shown was that they were not treated with Telon II, did not have Vydate in-furrow, & had not used any Temik. In the same season/area fields that had been treated with Vydate were fine, no Vydate = rejection. To View symptoms of TRV in foliage, including the deformed sprouts: http://oregonstate.edu/potatoes/Symptoms%20of%20TRV%20in%20Potato%20-%20Final.pdf.<br /> <br /> Jim C. pointed out that studies/observations they had done demonstrated that early infection of potato plants with TRV might show some foliage symptoms but did NOT result in tuber symptoms while late season infections resulted in CRS. This is because the virus moves poorly in potato plants (it doesn't need to move easily in the plant because it is spread by soil vectors, not above-ground insect vectors). CRS symptoms are caused when infected nematodes feed on tuber-producing stolons, not when they feed on other parts of the root system. Q:(Rob D.)Why is 'Sprang' such a big problem in Europe & not here, does it have anything to do with the instability of the virus. A:Symptoms are best expressed under cool cloudy conditions, as found in N. Europe, but not so much in US production areas.<br /> <br /> Phil H. showed a slide that indicated that Telon II, Vydate, & Temik worked well in controlling the nematode, Mocap worked sometimes, & water run metham sodium did not work. Q:How is TRV spread field-to-field? A:(Jim C.)In the Columbia Basin it is already widespread but at very low levels. It is likely the presence of various favored host-weed species in the preceding crop that contribute to it 'just showing up' in a potato field in any particular year. Q:(Rob D.)Does R. Norkotah show CRS symptoms? He asked this because CO has had fields that looked fine for years with no weeds to speak of, then all of a sudden after a RN crop, CRS showed up even though the RN tubers did not have symptoms. Could RN be a 'latent host' for TRV? A:(Jim C.)I do not think RN was a latent host for TRV & that such occurrences after RN were probably just coincidental in nature. He noted that in the last few years there we have experienced warmer drier weather, with more irrigation, & changes in the weed hosts present in fields (nightshade) that have likely contributed to situations where CRS just 'showed up'. <br /> <br /> *Phytoplasma-Joe M. showed slides & reviewed work done on Beet Leafhopper Transmitted Viroid Agent (BLTVA) that is prevalent in potatoes in the Columbia Basin (aka Purple Top). <br /> <br /> Trial #1 was a 3-year study of susceptibility of various potato cultivars to BLTVA. Varieties included R. Norkotah, Alturas, Umatilla, R. Burbank, Ranger R., Shepody, FL 1867, & FL 1879 grown in 5 row blocks, & naturally exposed to infected Leaf Hoppers. Symptomatic plants were flagged & later some were sent for confirmation of infection. RN had the highest infection rates, RB & FL 1867 had the lowest. A study was also conducted where caged plants were exposed to infected leafhoppers. At 35 days all varieties showed symptoms of BLTVA except RB which did not develop symptoms for 90 days. Q:(Nick)Were non-symptomatic plants also tested for BLTVA? A:Yes, some were tested (and were negative), but +scores were based on symptoms (only). Q:Could symptomatic plants be caused by some other phytoplasma? A:(Jim C.)In the Columbia Basin they have only found 'Group 6' phytoplasma. Joe said it was possible that some of the symptomatic plants may have been PLRV, but based on testing/experience this was probably less than 1% of the +plants. <br /> <br /> Trial #2 was a time of infection study that involved sequential exposure of previously caged plants to infected leafhoppers (naturally, i.e. rows of pre-emerged potato plats were caged to prevent exposure to LH & portions of the rows were removed each week). The plants were then examined for Purple Top symptoms. The data presented showed: most infection 10-15 days, little infection at 30-40 days, no infection after 50 days. Joe was not sure if this was due to mature plant resistance or changes in the leafhoppers. In 2009 they plan on introducing +BLTVA leafhoppers into caged plants each week to see if/how the potato plants get infected. That should help answer the question. Phil H. said that RDO felt they were getting infection damage late in the season. Joe said it is possible that plants infected at 53 days just didnt have enough time to show symptoms & would later in the season. Phil also mentioned that in the Hermiston area, growers who were spraying against leafhoppers in late May-early June were protecting their crop from developing Purple Top symptoms. The LH were present all season, but (evidently) were not transmitting BLTVA. Does this mean that BLTVA is not present all season or just that the LH can't effectively transmit it later on? Perhaps it is just a matter of the date symptom expression? Q:(JMc)Where does the original early season BLTVA come from? A:(Joe)Aphids collected off certain over-wintering weeds had lots of BLTVA. The BLTVA is transmitted through the eggs, which are laid on newly emerging potatoes, they then hatch on the potatoes & the nymphs infect the new potato plants. Thus over-wintering weeds in the 'wild areas' around fields are the original source of this phytoplasma. In June, as these areas dry down, the LH leave them & head to other green areas, which happen to be the new potato plants. If the borders were kept green, or a LH-susceptible crop was grown on the edges, this might reduce BLTVA spread to the crop. Soybean borders will not work (as they do for aphids) because leafhoppers dont like soybeans. Phil H. mentioned using Temik treated grass around the potatoes to trap & kill the LH (he does point out this is not a registered use for Temik).<br /> <br /> Trial #3 involved the study of the translocation of BLTVA from the plants into the tubers. Joe mentioned that the fry data for infected/non-infected tubers were the same. Do infected plants result in infected tubers? If so, how many? The same procedure was used, i.e., allowing potatoes to get naturally infected, flag +symptom plant, test for the presence of BLTVA, harvest +BLTVA plants individually & then test tubers for BLTVA. Results: Most tubers were infected (60-90%) though infection rates varied among varieties. Russet Burbank had the lowest infection rates (25%). <br /> <br /> Trail #4 involved a grow-out of the infected tubers & observed if they produced symptomatic/+BLTVA plants. Tubers had been stored at 48 F, 700 tubers were observed. Results: 35% of the infected tubers yielded infected plants. Tubers produced were small; in fact so small they would not have been harvested, making this a self-eliminating disease. There were no defects in the tubers produced. Q: Why were so many tubers from infected plants not infected? A: Perhaps it has to do with distribution of BLTVA in the tubers themselves (non-uniform). Jim C. said when they test these tubers they take 2 cores through the center of the tubers, but no work has been done to study the actual distribution of BLTVA in individual tubers. <br /> <br /> *Other Viruses<br /> <br /> US Plant Introduction Station-Jorge A. (USDA) in Beltsville, MD gave reported on how potato material is accepted, tested, & released into the US from abroad. The basic process of introduction: acquire material, tissue culture, test for Potato Spindle Tuber viroid (if plus discard), then PCR for Carlavirus, Leutovirus, & Potyvirus. If + they are put into therapy (thermo+virazol), if - run tests DNA for phytoplasma, Ralstonia, & ZC (?& other diseases?), if - release. Time from receipt to release is 3-4 months (if no virus), & additional time if therapy is required (up to 1yr). RT PCR is new to program.<br /> <br /> They intercepted two potential new viruses in 2008, one a seed-transmitted virus that causes rugosity ('frog-skin'-type symptoms) in potato leaves. Could not mechanically transmit this virus to a new host, could only transmit by grafting. Thus they have added grafting to the screen. The second virus intercepted was an easily mechanically transmitted Nepovirus. It was also seed-borne in true potato seed & had obvious symptoms in tobacco. They have also intercepted a new isolate of PVS from S. America. It had 94% homology with ordinary & Andean PVS strains, giving a strong + in PVS-ELISA, but having no symptoms on indicator host for PVS.<br /> <br /> Jorge commented that in the Andes where PMTV evolved, the bright yellowing symptoms induced by the virus was a 'sign of a good year'. He related how a local grower was upset that he was roguing the PMTV plants. He explained that the vector (Spongospora subterranea - Powdery Scab) did well in cool rainy seasons & these were the conditions that lead to a good crop! PMTV did not seem to be a concern in that area. Only 5-10% of the tubers from a PMTV infected plants become infected with PMTV.<br /> <br /> Disease status of selection received: Q:(Rob D.)Are selections received from Europe generally clean? A:Yes, if from Netherlands, Germany, Sweden, & Scotland. No, (PSTV & PVS)if from Poland & some other 'east block' countries. Selections from S. America caused the most problems (except those received from CIP which are normally clean but sometimes have PVS). Selections from Chili often have PVS.<br /> <br /> Q:(Alex)What type of therapy is used? A:Virazol+heat therapy. They are trying some new chemicals; one is a bacteriostatic chemical that slows down cell-to-cell movement of the virus. Therapy is only used if a virus is found in the initial screen, not routinely. Jorge also noted that they only keep the released lines for about ½ a year after release & then discard them (they dont have resources to keep them much longer). Besides being sent to the requestor, Un-protected varieties are sent to Sturgeon Bay (potato germplasm repository) after release. Variety ID is not part of the program. Recently many transgenic varieties are coming through the facility especially for BASF. McDonalds & Frito-Lay use to request potatoes in the past but not anymore.<br /> <br /> *Zebra Chip Update - Jim Crosslan gave what will likely be the last Zebra Chip report to the group because this disease is now known to be caused by a bacteria called Liberobacter. (See the attachment under minutes for more info).

Publications

Abad, J. A., J.W. Moyer, G.G. Kennedy, G.A. Holmes, and M.A. Cubeta. 2005. An Epidemic of Tomato spotted wilt virus on Potato in Eastern North Carolina. Amer. J. of Potato Res. 82:255-281. <br /> <br /> Abad, J. A., C. Loschinkohl, and M. Smither. 2008. Detection of an unknown virus in potato seedlings grown from true seed introduced from South America. 2008. Phytopathology 98:S9. <br /> <br /> Abad, J. A., M. Bandla, R. D. French-Monar, L. W. Liefting, and G. R. G. Clover. 2009. First report of the association of 'Candidatus Liberibacter' species with Zebra Chip (ZC) disease of infected potato plants in the USA. Plant Disease 93:108.<br /> <br /> Bolotova, Y., Karasev, A.V., and McIntosh, C. Statistical Analysis of the Laboratory Methods Used to Detect Potato Virus Y. Amer. J. Potato Res. 86, 2009 (in press, published on-line).<br /> <br /> Brown, C.R., H. Mojtahedi, J.M. Crosslin, S. James, B. Charlton, R.G. Novy, S.L. Love, M.I. Vales, and P. Hamm. 2009. Characterization of resistance to corky ringspot disease in potato: a case for resistance to infection by tobacco rattle virus. Am. J. Pot. Res. 86:49-55.<br /> <br /> Crosslin, J.M. and G. Bester. 2009. First report of Candidatus Liberibacter psyllaurous in zebra chip symptomatic potatoes from California. Plant Dis. (in press).<br /> <br /> Crosslin, J. M., and J.E. Munyaneza. 2009. Evidence that the zebra chip disease and the putative causal agent can be maintained in potatoes by grafting and in vitro. American Journal of Potato Research (in press).<br /> <br /> Crosslin, J.M., P.B. Hamm, K.S. Pike, T.M. Mowry, P. Nolte, and H. Hojtahedi. 2008. Management of Diseases caused by Viruses and Virus-like Pathogens. Potato Health Management 2nd Edition. APS Press. Chapter 17 (pages 160-170).<br /> <br /> Crosslin, J.M., and J.E. Munyaneza. 2008. Phytoplasma diseases of potatoes in the Northwest United States, pp. 128-129. In: S. Chiru, G. Olteanu, C. Aldea, and C. Badarau [eds.], 'Potato for a changing world'. Transilvania University of Brasov Publishing House, Brasov, Romania.<br /> <br /> Gudmestad, N.C., I. Mallik, J.S. Pasche, and J.M. Crosslin. 2008. First report of Tobacco rattle virus causing corky ringspot in potatoes grown in Minnesota and Wisconsin. Plant Dis. 92:1254.<br /> <br /> Hu, X., Meacham, T., Ewing, L., Gray, S.M., and Karasev, A.V.. A novel recombinant strain of Potato virus Y suggests a new viral genetic determinant of vein necrosis in tobacco. Virus Res. 2009 (in press).<br /> <br /> Karasev, A.V., Meacham, T., Hu, X., Whitworth, J., Gray, S.M., Olsen, N., and Nolte, P. Identification of Potato virus Y strains associated with tuber damage during a recent virus outbreak in potato in Idaho. Plant Dis. 92: 1371-1371, 2008.<br /> <br /> Kirk, W.W., S.L. Gieck, J.M. Crosslin and P.B. Hamm. 2008. The First Report of Corky Ringspot caused by Tobacco Rattle Virus on Potatoes (Solanum tuberosum) in Michigan. Plant Disease 92:485.<br /> <br /> Lin, H., H. Doddapaneni, J.E. Munyaneza, E.L. Civerolo, V.G. Sengoda, J.L. Buchman, and D.C. Stenger. 2009. Molecular characterization and phylogenetic analysis of 16S rRNA from a new 'Candidatus Liberibacter' strain associated with zebra chip disease of potato (Solanum tuberosum L.) and the potato psyllid (Bactericera cockerelli Sulc). Journal of Plant Pathology 91: 213-217.<br /> <br /> Munyaneza, J.E., A.S Jensen, P.B. Hamm, and J.E. Upton. 2008. Seasonal occurrence and abundance of beet leafhopper in the potato growing region of Washington and Oregon Columbia Basin and Yakima Valley. American Journal of Potato Research 85: 77-84.<br /> <br /> Munyaneza, J.E., and J.M. Crosslin. 2008. Zebra chip, a new potato disease in North and Central America, is associated with the potato psyllid, pp. 124-127. In: S. Chiru, G. Olteanu, C. Aldea, and C. Badarau [eds.], 'Potato for a changing world'. Transilvania University of Brasov Publishing House, Brasov, Romania.<br /> <br /> Munyaneza, J.E., J.L. Buchman, J.E. Upton, J.A. Goolsby, J.M. Crosslin, G. Bester, G.P. Miles, and V.G. Sengoda. 2008. Impact of different potato psyllid populations on zebra chip disease incidence, severity, and potato yield. Subtropical Plant Science 60:27-37.<br /> <br /> Munyaneza, J.E., V.G. Sengoda, J.M. Crosslin, G. De la Rosa-Lozano, and A. Sanchez. 2009. First report of Candidatus Liberibacter psyllaurous in potato tubers with zebra chip disease in Mexico. Plant Disease (in press). <br /> <br /> Munyaneza, J.E., J.M. Crosslin, J.E. Upton, and J.L. Buchman. 2009. Incidence of BLTVA phytoplasma in local populations of Circulifer tenellus (Hemiptera: Cicadellidae) in Washington State. Journal of Insect Science (in press).<br /> <br /> Navarre, D.A., R. Shakya, J. Holden, and J.M. Crosslin. 2009. LC-MS analysis of phenolic compounds in tubers showing zebra chip symptoms. Am. J. Pot. Res. (in press).<br /> <br /> Nitzan, N., R.A. Boydston,D. Batchelor, J.M. Crosslin, L. Hamlin, and C.R. <br /> Brown. 2009. Hairy nightshade is an alternative host of Spongospora subterranea, the potato powdery scab pathogen. Am. J. Pot. Res. (in press).<br /> <br /> Ottoman, R.J., D.C. Hane, C.R. Brown, S. Yilma, S.R. James, A.R. Mosley, J.M. Crosslin, and M.I. Vales. 2009. Validation and implementation of marker-assisted selection (MAS) for PVY resistance (Ryadg gene) in a tetraploid potato breeding program. Am. J. Pot. Res. http://www.springerlink.com/content/8205108r86227147/fulltext.html DOI 10.1007/s12230-009-9084-0<br /> <br /> Srinivasan, R., and J.M. Alvarez, 2008. Hairy nightshade as a potential Potato leafroll virus (Luteoviridae: Polerovirus) inoculum source in Pacific Northwest potato ecosystems. Phytopathology. 98: 985-991. <br /> <br /> Srinivasan, R., J.M. Alvarez, N. Bosque-Perez, S. Eigenbrode, and.R. Novy. 2008. Effect of an alternate weed host, hairy nightshade, Solanum sarrachoides (Sendtner), on the biology of the two most important Potato leafroll virus (Luteoviridae: Polerovirus) vectors, Myzus persicae (Sulzer) and Macrosiphum euphorbiae (Thomas) (Aphididae: Homoptera). Environmental Entomology. 37: 592-600. <br /> <br /> Srinivasan, R., and J.M. Alvarez, 2007. Effect of mixed-viral infections (Potato virus Y-Potato leafroll virus) on the biology and preference of vectors, Myzus persicae (Sulzer) and Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae). Journal of Economic Entomology. 100: 646-655. <br /> <br /> Whitworth, J.L., R.G. Novy, D.G. Hall, J.M. Crosslin, and C.R. Brown. 2009. Characterization of broad spectrum Potato virus Y resistance in a Solanum tuberosum ssp. andigena-derived population and select breeding clones using molecular markers, grafting, and field inoculations. Am. J. Pot. Res. http://www.springerlink.com/content/bl05568j57nk2r18/fulltext.html DOI 10.1007/s12230-009-9082-2

Impact Statements

1. BLTVA: Role of psyllids in transmission of BLTVA and development of control strategies for the disease caused by this pathogen.
2. PVY Characterization: Identification of a new 1F5 antibody for accurate characterization of the "O5" strain of PVY and refinement of the interactions between potato variety, PVY strains, and methods of inoculation.
3. Necrotic Virus Management Plan: Revised and updated, based on data obtained through the bi-lateral "Scoping Survey" work, thereby allowing trade between US and Canada to continue uninterrupted.
4. TRV/CRS work: Detection of the presence of TRV in states outside the Pacific Northwest, recognition of new symptoms, and recommending Vydate based control measures for this nematode-virus complex.

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Report Information

Participants

Alvarez, Juan Manuel (jalvarez@uidaho.edu) - University of Idaho; Boze, Doug (dboze@idahocrop.com) - Idaho CIA; Crosslin, Jim (jim.crosslin@ars.usda.gov) - USDA-ARS; Davidson, Robert (rddavid@ext.colostate.edu) - Colorado State University; Eggers, Jordan (mailto:Jordan.Eggers@oregonstate.edu) - Oregon State University; French, Allan (allan.french@simplot.com) - Simplot NAFG/Idaho; Gray, Stewart (smg3@cornell.edu) - USDA-Cornell; Guzman, Pablo (pguzman@ucdavis.edu) - Ca CIA \ UC Davis; Hamm, Phil (philip.b.hamm@oregonstate.edu) - Oregon State University; Hane, Dan (dan.hane@oregonstate.edu) - Oregon State University; Jensen, Andy (ajensen@potatoes.com) - Washington Potato Commission; Karasev, Alex (akarasev@uidaho.edu) - University of Idaho; Marquerdt, Steve (skmarquardt@earthlink.net) - North Dakota State Seed Department; McMorran, Jeff (jeff.mcmorran@oregonstate.edu) - OR Potato Certification \ OSU; Munyaneza, Joe (joseph.munyaneza@ars.usda.gov) - USDA-ARS, Wapato, WA; Nakhla, Mark (Mark.K.Nakhla@aphis.usda.gov) - APHIS Beltsville; Nolte, Phillip (pnolte@vidaho.edu) - University of Idaho; Pavek, Mark (mjpavek@wsu.edu) - Washington State University; Sather, Kent (ksather@lamar.colostate.edu) - Colorado State University; Siemsen, Susie (uplss@montana.edu) - Montana State University; Snell, Rue (rues@lamar.colostate.edu) - Co Certification Sv. \ CoSU; Sutula, Chet (chet@agdia.com) - Agdia; Wei, Fusheng (fushengw@Ag.arizona.edu) - Arizona SU (Pathology); Whitworth, Jonathan (jonathan.whitworth@ars.usda.gov) - ARS-USDA, Aberdeen, ID; Zidack, Nina (nzidack@montana.edu) - Montana State University

Brief Summary of Minutes

1) Call to order (8:10 AM). Stewart requested copies of hotel receipts for rebate and registration was set at $40. He announced that no Administrative Advisor was present this year (Greg Bohach has left UI). He reminded attendees that a new proposal to renew WERA089 project is needed. It was suggested to set a small committee to help prepare the proposal; this committee will include Jeff McMorran, Stewart Gray, Rob Davidson, and Phil Hamm.

2) Approval of minutes: minutes were approved; however, it was brought to the attendee attention that the committee (Phil N., Phil H., Rob D., Gary F., Alex K., and Steve M.) that was supposed to work on the process of the Outstanding Multidisciplinary Resources Award for 2010 - failed to do so.

3) Introductions. See list of attendees (above).

4) Agenda: approved

5) Stewart Gray briefly discussed the - Schultz Virus Collection - currently being maintained at ARS Beltsville and was in the process of being gotten rid off; the discussion was set to continue the following day.

6) Reports on Seed Certification

Washington - Mark Pavek mentioned that PVY levels came down this past season and nothing else unusual had been observed. Rob D. asked whether all the seed lots were tested with ELISA and the answer was no; the inspection was only done visually. Jim Crosslin reported one zebra chip-infected plant found in the WA seed lot trial at Othello; the liberibacter-infected plant was found in only one seed lot that originated from Wyoming.

Oregon - Jeff McMorran mentioned that nothing unusual was observed during the season; he however reported that there were some issues with chemicals that had been previously applied for mint in the potato fields.

California - Pablo Guzman discussed PVY issues with different potato planting dates. An early (February)-planted seed lot was rejected because of PVY. This happened only in one location and the reasons for the high PVY/aphid levels were unknown. There was also a problem with potato tuber skin cracking (var. White Rose) and a couple of tubers were found with PVY-N. Alex K. does not think it was a PVY issue with that particular field because testing did not really reveal PVY infection. There is a probability that the cracking was due to herbicides.

Colorado - Kent Sather reported that potato acreage decreased about 2,000 acres mainly because of rejections of Norkotah (about 1,800 acres) during the summer inspection. No PLRV was seen in CO this year. Post harvest testing was conducted in Yuma, AZ. Plots in Yuma looked good except for Norkotah lots which showed distinctive PVY symptoms. Rob D. reported that there was a lot of rain in cropping areas and a lot of Norkotah were not harvested because of ring rot. He also mentioned that a lot of aphids (all species) were observed because of warm season, leading to very high levels of PVY. Norkotah is not making it to G3. Although a lot of Norkotah are being grown because of high fresh market demand, Norkotah seed production is declining because of PVY. All growers are now required to plant certified seed (PVY tolerance levels: 2% summer inspection, 4% winter grow-out, and 10% at planting). A substantial discussion on state seed PVY related re-certification laws ensued.

Idaho - Doug Boze provided a handout summarizing results of winter tests from 2002-2009 and explained that rejection for PVY was reduced in 2009. More Norkotah are being grown but PVY situation has improved. Winter test was conducted in CA and 100% PVY ELISA testing was conducted. Alex K. and Phil N. reported testing samples for PVY strains. Some cultivars were more hard hit than others and none of the lots visited was under 20% infection. However, because of seed shortage of some varieties, the seed was planted anyway. When the plants emerged, no PVY symptoms were apparent, but when testing was conducted, 10-15% more PVY infection was detected, especially in Russet Burbank. Alex and Phil are conducting a survey on PVY necrotic strains in seed lots and mixed infections of PVYo and PVYntn have been observed/detected. The research is being funded by the state and CSREES-SCRI grants.

Montana - Nina Zidack reported that a severe frost led to about 15% seed field loss. Very low levels of PVY were observed this year. Rejection of only 2 lots took place. Winter grow-out was conducted in Hawaii, which is a very good location to pick symptoms of PVY.

Nebraska - Steve Marquardt reported that the seed acreage is almost staying the same. About 90% of the seed lots passed inspection/certification and the only reason for rejection was PVY. No PVY pressure in commercial production was observed.

7) Research and Extension Reports

Alex Karasev - talked about the identification and molecular characterization of the new L26 PVY strain. L26 strain was isolated from potatoes in Idaho and induces typical necrotic NTN symptoms in Yukon Gold tubers. It also induces potato tobacco necrosis (PTNRD). L26 is a recombinant between PVYz and PVYntn and the suggested genetic classification is PVYz/ntn.

Phil Hamm - talked about the impact of PVY strains on 8 potato cultivars. Conducted a study in the screenhouse to determine above and belowground symptoms caused by PVYo, PVYntn, and PVYn:o. Varieties tested include Premier, Alturas, Yukon Gem, Ranger, Norkotah, Yukon Gold, Russet Burbank, and Blazer Russet. There was substantial yield loss due to PVY. Yukon Gem showed very low PVY infection in both 2008 and 2009. No or little tuber symptoms in Premier, Burbank, and Blazer. Not all strains of PVY infect plants at the same frequency, produce the same foliage or tuber symptoms, and have the same impact on yield. Alternatively, a same PVY strain may not infect plants at the same frequency, produce the same foliage or tuber symptoms and have the same impact on yield. HOWEVER, PVY REDUCES YIELD.

Stewart Gray - talked about the intragenic resistance to PVY. Growers should be concerned with necrosis in tubers and concentrate on those varieties that express tuber necrosis symptoms. Many resistance genes in various plant families encode eIF4E which is a cap-binding protein for viruses. Transformed potatoes using this gene produced PVY resistant lines, with zero infection in these resistant lines.

Jonathan Whitworth - talked about a high through-put for post-harvest PVY testing. His Aberdeen lab has developed an RT-PCR testing for all PVY strains. The technique is cheaper compared to currently existing testing methods. A discussion on whether this testing is feasible and practical or can replace the winter grow-out ensued.

Phil Nolte - talked about PVY management for seed potato producers. He discussed his recommendations via a newsletter (bulletin) to growers on how to prevent PVY spread. The publication is online and collaborators on the project are Juan Alvarez and Jonathan Whitworth.

Alex Karasev - talked about PVY ordinary and necrotic strains in Idaho. He discussed the European historical experience with PVY. He also discussed a US national survey that was conducted in 2004-2006 and focused on late generation seed lots. During that survey, uneven distribution of NTN between states was observed. Almost all necrotic PVY strains were NTN; however, no N was found. In addition, he discussed current PVY monitoring in Idaho. In 2009, Cal White and Norkotah showed no visible symptoms but high levels of PVY were detected after testing. He pointed out that NTN is in Idaho, dominant necrotic strain, and unevenly distributed in the state, with an overall incidence of 21%. PVYo is dominant near Idaho Falls. Incidence of NTN did not increase between 2001 and 2009. Monitoring PVY is necessary. Buy clean seed was his recommendation.

Juan Manuel Alvarez talked about hairy nightshade (HNS) as a significant source of inoculum for PVY. He discussed aphids-HNS-virus interactions. HNS produces a lot of seed and is everywhere. This weed is magnet for aphids and they reproduce much better on this host, especially when plants are infected with viruses. Transmission studies conducted between potato and HNS to investigate HNS as source of inoculums were successful. Studies determined PVY concentration 15 and 30 days after planting after inoculation using aphids and both potato and HNS plants. Virus titer was much higher in inoculated leaves and the ones below after 15 days than after 30 days (after germination). He concluded that HNS plays a major role in the epidemiology of PLRV and PVY in the potato ecosystem.

Jim Crosslin - reported on his recent partial characterization of an isolate of cherry leaf roll virus transmitted through true seed of Solanum acaule. Potatoes can be infected with this virus but not show symptoms. This virus is probably seed-borne in other host plants.

Joe Munyaneza - gave a research update on potato purple top disease. Studies were conducted under screenhouse to accurately determine timing to stop insecticide sprays targeted against the beet leafhopper, insect vector of BLTVA phytoplasma that causes purple top in potatoes. In addition, studies were to determine the relationship between beet leafhopper density and the likelihood of BLTVA transmission and purple top development, with the ultimate goal of developing action thresholds for the beet leafhopper. Preliminary results suggest that younger potato plant growth stages appear more susceptible to BLTVA than older ones. Density as low as 1 beet leafhopper per plant can cause significant BLTVA infection, especially in younger plants. Further studies are needed to establish action thresholds for the beet leafhopper management.

Joe Munyaneza - gave a research update on zebra chip potato disease. The disease has been documented in southwestern US, Mexico, Central America, and New Zealand, and is causing losses of millions dollars to the potato industry. The disease is associated with a previously undescribed species of liberibacter transmitted by the potato psyllid. Recent studies conducted in Munyaneza lab showed that the potato psyllid can acquire the bacterium in as a short time as 1 hour and effectively inoculate the bacterium into potato plants in about 2 hours. Preliminary results also indicated that as few as 1 potato psyllid per plant is enough to cause zebra chip, significantly reduce yield and increase reducing sugars. It takes 3 weeks or less for zebra chip symptoms to develop in potato tubers after plants exposure to infective potato psyllids. Moreover, it was demonstrated that, to cause zebra chip, the psyllids have to carry liberibacter; however, liberibacter-free psyllids can significantly affect yield. Low temperatures were shown to slow down liberibacter development whereas extreme temperatures inhibit development of this bacterium. Furthermore, most of, if not, all existing potato cultivars in the Pacific Northwest/US are severely affected by zebra chip.

Mark Nakhla - talked about development of PCR-based assays for targeted viruses in foreign germplasm at APHIS-NPGBL. This method uses CANARY Biosensors for rapid detection of regulated plant pathogens, including viruses. B-cells that express pathogen-specific Abs and aequorin are used with this rapid detection technique.

Stewart Gray - discussed in details the Schultz Virus Collection in Beltsville. It consists of viruses (about 54 samples) mainly maintained in potato tubers, grown in cages every year and also tested with ELISA on a regular basis. Some tubers however are contaminated with several other viruses. He was trying to find out if anybody would be interested in taking and relocating the collection. A couple of people in the group (including Jim C., Chet S., and maybe Gary F.) were interested in the collection for some uses. There was a suggestion to grow the tubers one more year and then lyophilize them (then keep them that way). The collection moved to Beltsville from Maine.

Phil Hamm - briefly discussed powdery scab and mop-top issues. He would like to receive soil samples from other locations/states. He has a permit to import soil samples from most of the states.

Jim Crosslin - mentioned a grant awarded by NPC-ARS Potato program to him and Neil Gudmestad (North Dakota State University) to survey tuber necrosis in potatoes. He would like to receive tuber samples with all kinds of necrosis; he has import permit.

Stewart Gray - suggested putting together a collection of pictures showing virus symptoms and these pictures could probably be posted online. This picture collection could serve as a diagnostic tool for viruses to the potato producers and researchers.

Stewart Gray and Jeff McMorran - discussed the renewal of the WERA089 Project Grant. The renewal must be in 6 months in advance, scope should be broadened to include other 'virus-like' agents and/or diseases vectored by insects (in a virus-like manner), including Zebra Chip/liberibacter. Subcommittee to work on this should include: Jeff McMorran, Stewart Gray, Joe Munyaneza, Nina Zidack, Mark Nakhla, and others.

Jeff McMorran - suggested preparation of a 5-10 minute PPT presentation that would convince commercial growers that they should be concerned about the affects of PVY on the yield and quality of their potato crops. It would be mostly a picture based format, using limited amount of tables/graphs. Of preference would be data that visually show data obtained from studies (i.e. two piles of potatoes showing +PVY vs. no PVY, and internal and external defects). Relating how this is a problem that needs to be address on a broad scale (not just farm scale) basis should be emphasized. The thought is to have this presented across the U.S at winter meetings and perhaps at the SPRO meeting this summer. Title might be "Grow Profits, not Problems'. Subcommittee should include: Jon W., Phil H. Rob D. Phil N., Alex P., and maybe others.

Stewart Gray - briefly discussed the Memorandum of Understanding (MOU) on PVY in seed potatoes between states and the related Management Plan.

8) Impact Statements

Ideas suggested include (1) PVY impacts on yield and quality; (2) Identification reservoirs for PVY; (3) Identification and characterization of a new virus to potatoes - Cherry Leafroll Virus; (4) Continuing work on spread and control of Zebra Chip; (5) Obtaining big grant to study PVY strains in the U.S.; others? Subcommittee to work on this should include: Jeff McMorran, Joe M., Phil Nolte, Dan Hane, Kent S., and maybe others.

9) Election of secretary - Nina Zidack was elected unanimously to become Secretary of the group.

10) Meeting adjourned at 10:55 on March 12.

Accomplishments

The identification and molecular characterization of the new L26 PVY strain. L26 strain isolated from potatoes in Idaho. This strain induces typical necrotic NTN symptoms in Yukon Gold tubers and induces potato tobacco necrosis (PTNRD). L26 is a recombinant between PVYz and PVYntn and the suggested genetic classification is PVYz/ntn. Alex Karasev<br /> <br /> <br /> Further documentation of the impact of PVY strains on 8 potato cultivars. Screenhouse studies were used to determine above and belowground symptoms caused by PVYo, PVYntn, and PVYn:o. Varieties tested include Premier, Alturas, Yukon Gem, Ranger, Norkotah, Yukon Gold, Russet Burbank, and Blazer Russet. There was substantial yield loss due to PVY. Yukon Gem showed very low PVY infection in both 2008 and 2009. No or little tuber symptoms in Premier, Burbank, and Blazer. Not all strains of PVY infect plants at the same frequency, produce the same foliage or tuber symptoms, and have the same impact on yield. Alternatively, a same PVY strain may not infect plants at the same frequency, produce the same foliage or tuber symptoms and have the same impact on yield. The over all negative impact of PVY on yield was evident. Phil Hamm<br /> <br /> <br /> The intragenic resistance to PVY was demonstrated showing that growers should be concerned with necrosis in tubers and concentrate on those varieties that express tuber necrosis symptoms. Many resistance genes in various plant families encode eIF4E which is a cap-binding protein for viruses. Transformed potatoes using this gene produced PVY resistant lines, with zero infection in these resistant lines. Stewart Gray<br /> <br /> <br /> A high throughput system for post-harvest PVY testing was developed at the ARS lab in Aberdeen using a RT-PCR testing for all PVY strains. The technique is cheaper compared to currently existing testing methods. A discussion on whether this testing is feasible and practical or can replace the winter grow-out ensued. Jonathan Whitworth<br /> <br /> <br /> PVY management techniques for seed potato producers were developed and made widely available to potato producers and educators via a newsletter (bulletin), Extension publications, and web postings. These recommendations emphasize the means for growers to prevent local and regional spread of PVY. The publication is online and collaborators on the project are Juan Alvarez and Jonathan Whitworth and Phil Nolte.<br /> <br /> <br /> Further information on the presence of ordinary and necrotic strains of PVY in Idaho was summarized as well as the European historical experience with PVY. NTN is in Idaho, was the dominant necrotic strain, and was unevenly distributed in the state. The overall incidence of this virus strain was 21%. PVYo is dominant near Idaho Falls. Incidence of NTN did not increase between 2001 and 2009. In 2004-2006 a US national survey was conducted and focused on late generation seed lots. During that survey, uneven distribution of NTN between states was observed. Almost all necrotic PVY strains were NTN; however, no N was found. PVY monitoring continues in Idaho. In 2009, Cal White and Norkotah showed no visible symptoms but high levels of PVY were detected after testing. Monitoring PVY is necessary. The overall recommendation for controlling this virus is to Buy clean seed. Alex Karasev<br /> <br /> <br /> Further work documentation hairy nightshade (HNS) as a significant source of inoculum for PVY was completed. Aphids-HNS-virus interactions were better charterized. HNS produces a lot of seed and is everywhere. This weed is magnet for aphids and they reproduce much better on this host, especially when plants are infected with viruses. Transmission studies conducted between potato and HNS to investigate HNS as source of inoculums were successful. Studies determined PVY concentration 15 and 30 days after planting after inoculation using aphids and both potato and HNS plants. Virus titer was much higher in inoculated leaves and the ones below after 15 days than after 30 days (after germination). He concluded that HNS plays a major role in the epidemiology of PLRV and PVY in the potato ecosystem. Juan Manuel Alvarez<br /> <br /> <br /> An isolate of Cherry Leaf Roll Virus transmitted through true seed of Solanum acaule was characterized. Potatoes can be infected with this virus but not show symptoms. This virus is probably seed-borne in other host plants. Jim Crosslin<br /> <br /> <br /> Screenhouse studies were used to study pesticide timing effects of control of Potato Purple Top Disease. Studies were conducted to accurately determine timing to stop insecticide sprays targeted against the beet leafhopper, insect vector of BLTVA phytoplasma that causes purple top in potatoes. In addition, studies were used to determine the relationship between beet leafhopper density and the likelihood of BLTVA transmission and purple top development, with the ultimate goal of developing action thresholds for the beet leafhopper. Preliminary results suggest that younger potato plant growth stages appear more susceptible to BLTVA than older ones. Density as low as 1 beet leafhopper per plant can cause significant BLTVA infection, especially in younger plants. Further studies are needed to establish action thresholds for the beet leafhopper management. Joe Munyaneza<br /> <br /> <br /> Current research on Zebra Chip potato disease was summarized. The disease has been documented in southwestern US, Mexico, Central America, and New Zealand, and is causing losses of millions dollars to the potato industry. The disease is associated with a previously undescribed species of liberibacter transmitted by the potato psyllid. Recent studies conducted in Munyaneza lab showed that the potato psyllid could acquire the bacterium in as a short time as 1 hour and effectively inoculate the bacterium into potato plants in about 2 hours. Preliminary results also indicated that as few as 1 potato psyllid per plant is enough to cause zebra chip, significantly reduce yield and increase reducing sugars. It takes 3 weeks or less for zebra chip symptoms to develop in potato tubers after plants exposure to infective potato psyllids. Moreover, it was demonstrated that, to cause zebra chip, the psyllids have to carry liberibacter; however, liberibacter-free psyllids can significantly affect yield. Low temperatures were shown to slow down liberibacter development whereas extreme temperatures inhibit development of this bacterium. Furthermore, most of, if not, all existing potato cultivars in the Pacific Northwest/US are severely affected by zebra chip. Joe Munyaneza<br /> <br /> <br /> A PCR-based assay for targeted viruses in foreign germplasm was developed at APHIS-NPGBL. This method uses CANARY Biosensors for rapid detection of regulated plant pathogens, including viruses. B-cells that express pathogen-specific Abs and aequorin are used with this rapid detection technique. Mark Nakhla<br /> <br /> <br /> Research grants to allow the further study of powdery scab and mop-top (Phil Hamm) and tuber necrosis in potatoes (Jim Crosslin) were received and samples of soil and tubers are needed.<br />

Publications

Bolotova, Y., Karasev, A.V., and McIntosh, C. 2009. Statistical analysis of the laboratory methods used to detect Potato virus Y. Amer. J. Potato Res. 86, 265-271.<br /> <br /> Crosslin, J. M., and J.E. Munyaneza. 2009. Evidence that the zebra chip disease and the putative causal agent can be maintained in potatoes by grafting and in vitro. American Journal of Potato Research 86: 183-187.<br /> <br /> Crosslin, J.M. 2009. Detection of tobacco rattle virus RNA in processed potato chips displaying symptoms of corky ringspot disease. HortScience 44:1790-1791.<br /> <br /> Crosslin, J.M., I. Mallik, and N.C. Gudmestad. 2009. First report of Tomato spotted wilt virus causing potato tuber necrosis in Texas. Plant Dis. 93:845.<br /> <br /> Crosslin, J.M., J.E. Munyaneza, J.K. Brown, and L.W. Liefting. 2010. Potato zebra chip disease: a phytopathological tale. Plant Health Progress doi:10.1094/PHP-2010-0317-01-RV.<br /> <br /> Crosslin, J.M., K.C. Eastwell, C.M. Davitt, and J.A. Abad. 2010. First report of seed-borne Cherry leaf roll virus in wild potato, Solanum acaule, from South America. Plant Dis. (in press).<br /> <br /> Crosslin, J.M., P.B. Hamm, W.W. Kirk, and R.W. Hammond. 2010. Complete genomic sequence of a tobacco rattle virus isolate from Michigan-grown potatoes. Arch. Virol. 155:621-625.<br /> <br /> Gharalari, A.H., C. Nansen, D.S. Lawson, J. Gilley, J.E. Munyaneza, and K. Vaughn. 2009. Knockdown mortality, repellency and residual effects of insecticides for control of adult Bactericera cockerelli (Homoptera: Psyllidae). Journal of Economic Entomology 102: 1032-1038.<br /> <br /> Hu, X., Karasev, A.V., Brown, C.J., and Lorenzen, J.H. 2009. Sequence characteristics of Potato virus Y recombinants. J. Gen. Virol. 90, 3033-3041.<br /> <br /> Hu, X., Meacham, T., Ewing, L., Gray, S.M., and Karasev, A.V. 2009. A novel recombinant strain of Potato virus Y suggests a new viral genetic determinant of vein necrosis in tobacco. Virus Res. 143, 68-76.<br /> <br /> Karasev, A.V., Nikolaeva, O.V., Hu, X., Sielaff, Z., Whitworth, J., Lorenzen, J.H., and Gray, S.M. 2010. Serological properties of ordinary and necrotic isolates of Potato virus Y: a case study of PVYN misidentification. Amer. J. Potato Res. 87, 1-9.<br /> <br /> Lin, H., H. Doddapaneni, J.E. Munyaneza, E.L. Civerolo, V.G. Sengoda, J.L. Buchman, and D.C. Stenger. 2009. Molecular characterization and phylogenetic analysis of 16S rRNA from a new Candidatus Liberibacter strain associated with zebra chip disease of potato (Solanum tuberosum L.) and the potato psyllid (Bactericera cockerelli Sulc). Journal of Plant Pathology 91: 213-217.<br /> <br /> Lin, Y-H., K.L. Druffel, J. Whitworth, M.J. Pavek, and H.R. Pappu. 2009. Molecular characterization of two Potato Virus S isolates from late blight resistant genotypes of potato (Solanum tuberosum). Arch Virol 154:18611863.<br /> <br /> Miles, G.P., J.L. Buchman, and J.E. Munyaneza. 2009. Impact of Zebra Chip Disease on the Mineral Content of Potato Tubers. American Journal of Potato Research 86:481-489.<br /> <br /> Miles, G.P., M.A. Samuel, J. Chen, E.L. Civerolo, and J.E. Munyaneza. 2010. Evidence that cell death is associated with zebra chip disease in potato tubers. American Journal of Potato Research (in press).<br /> <br /> Munyaneza, J.E., J.M. Crosslin, and J.L. Buchman. 2009. Seasonal occurrence and abundance of the potato psyllid, Bactericera cockerelli, in south central Washington. Am. J. Pot. Res. 86:513-518.<br /> <br /> Munyaneza, J.E., J.M. Crosslin, and J.L. Buchman. 2009. Susceptibility of different potato cultivars to purple top disease. Am J. Pot. Res. 86:499-503.<br /> <br /> Munyaneza, J.E., J.M. Crosslin, J.E. Upton, and J.L. Buchman. 2010. Incidence of the beet leafhopper-transmitted virescence agent phytoplasma in local populations of the beet leafhopper, Circulifer tenellus, in Washington State. J. Insect Sci. 10:1-10.<br /> <br /> Munyaneza, J.E., J.M. Crosslin, J.L. Buchman, and V.G. Sengoda. 2010. Susceptibility of different potato plant growth stages to purple top disease. Am. J. Pot. Res. 87:60-66.<br /> <br /> Munyaneza, J.E., T.W. Fisher, V.G. Sengoda, S.F. Garczynski, A. Nissinen, and A. Lemmetty. 2009. First report of Candidatus Liberibacter Solanacearum associated with psyllid-affected carrots in Europe. Plant Disease 94: 639. <br /> <br /> Munyaneza, J.E., V.G. Sengoda, J.M. Crosslin, G. De la Rosa-Lozano, and A. Sanchez. 2009. First report of Candidatus Liberibacter psyllaurous in potato tubers with zebra chip disease in Mexico. Plant Disease 93: 552.<br /> <br /> Munyaneza, J.E., V.G. Sengoda, J.M. Crosslin, J. Garzon-Tiznado, and O. Cardenas-Valenzuela. 2009. First Report of 'Candidatus Liberibacter solanacearum' in Tomato Plants in Mexico. Plant Disease 93: 1076. <br /> <br /> Munyaneza, J.E., V.G. Sengoda, J.M. Crosslin, J. Garzon-Tiznado, and O. Cardenas-Valenzuela. 2009. First Report of 'Candidatus Liberibacter solanacearum' in Pepper in Mexico. Plant Disease 93: 1076.<br /> <br /> Nolte, P, JM. Alvarez and JL Whitworth. 2009. Potato Virus Y Management for the Seed Potato Producer. University of Idaho CIS #1165. Available online at: http://info.ag.uidaho.edu/catalog<br /> <br /> Pantoja, A., A.M. Hagerty, S.Y. Emmert, and J.E. Munyaneza. 2009. Leafhoppers (Homoptera: Cicadellidae) associated with potatoes in Alaska: species composition, seasonal abundance, and potential phytoplasma vectors. American Journal of Potato Research 86: 68-75.<br /> <br /> Riga, E., R. Larsen, K. Eastwell, N. Guerra, L. Guerra, and J.M. Crosslin. 2009. Rapid detection of Tobacco rattle tobravirus in viruliferous Paratrichodorus allius from greenhouse and field specimens. J. Nematology 41:60-63.<br /> <br /> Sengoda, V.G., J.E. Munyaneza, J.M. Crosslin, J.E. Buchman, and H.R. Pappu. 2010. Phenotypic and etiological differences between psyllid yellows and zebra chip diseases of potatoes. Am. J. Pot. Res. 87:41-49.<br />

Impact Statements

1. Further study and documentation of the impact of PVY on yield and quality of potatoes in the US.
2. Identification of natural reservoirs for PVY and documentation of the importance of natural weed host in managing of the spread of PVY into US potato crops.
3. Identification and characterization of a new virus threats to potatoes i.e., Cherry Leafroll Virus, novel strains of tuber deforming PVY.
4. Continuing work on spread and control of Zebra Chip.

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Report Information

Participants

Bajet, Narceo (narceoba@eurofinsus.com)  Eurofins STA Laboratories;Boze, Doug (dboze@idahocrop.com) - Idaho CIA;Crosslin, Jim (jim.crosslin@ars.usda.gov) - USDA-ARS;Davidson, Robert (rddavid@ext.colostate.edu) - Colorado State University;Eggers, Jordan (mailto:Jordan.Eggers@oregonstate.edu) - Oregon State University;Eid, Sahar (seid@uidaho.edu)  University of Idaho;Guzman, Pablo (pguzman@ucdavis.edu) - Ca CIA \ UC Davis;Hall, Darren (Darren.hall@ars.usda.gov)  USDA-ARS;Hamm, Phil (philip.b.hamm@oregonstate.edu) - Oregon State University;Jensen, Andy (ajensen@potatoes.com) - Washington Potato Commission;Karasev, Alex (akarasev@uidaho.edu) - University of Idaho;Marquardt, Steve (smarquardt@nebraskapotatoes.com) - Nebraska Seed Department;McMorran, Jeff (jeff.mcmorran@oregonstate.edu) - OR Potato Certification \ OSU;Munyaneza, Joe (joseph.munyaneza@ars.usda.gov) - USDA-ARS, Wapato, WA;Nolte, Phillip (pnolte@vidaho.edu) - University of Idaho;Pavek, Mark (mjpavek@wsu.edu) - Washington State University;Sather, Kent (ksather@lamar.colostate.edu) - Colorado State University;Siemsen, Susie (uplss@montana.edu) - Montana State University;Singh, Mathuresh (msingh@potatoesnb.com)  New Brunswick Seed Department;Snell, Rue (rues@lamar.colostate.edu) - Co Certification Sv. \ CoSU;Sutula, Chet (chet@agdia.com)  Agdia;Thornton, Mike (mike@uidaho.edu)  University of Idaho;Whitworth, Jonathan (jonathan.whitworth@ars.usda.gov) - ARS-USDA, Aberdeen, ID;Zidack, Nina (nzidack@montana.edu) - Montana State University

Brief Summary of Minutes

2011 WERA089 Minutes
March 10-11, 2011
Hotel Arizona, Tucson, Az
Chair: Jeff McMorran, Oregon State University
Vice-Chair: Joe Munyaneza, USDA-ARS
Secretary: Nina Zidack, Montana State University
Administrative Advisor: Donn Thill, University of Idaho, Moscow, ID (absent)

Call to Order (8:15 AM). Introductions and affiliations of attendees. Jeff announced that Donn Thill was not able to attend. He sent an e-mail that we had a temp designation of Temp341 which has been approved and will officially commence on October 1, running for 5 years. WERA 089 initiated October 2006 and terminates September 30 of 2011. Annual report will be filed by chair (Joe Munyaneza). The report should be an accumulation of accomplishments and impacts over the duration of the project. Jeff distributed agenda and described the purpose of this meeting, an informal discussion between certification, research and industry participants.

Approval of Minutes

State Reports on Seed Certification

Colorado: Kent Sather presented certification process in CO and presented data on seed potato acreages since 1995. Most states have declined in acreage. Colorado had a big spike in early 2000s with increases in Russet Norkotah, but as PVY increased, Norkotah acreage decreased and total acreage declined towards 2010. Jonathon Whitworth, some of acreage decline also due to higher pack-out of newer varieties compared to Russet Burbank. Rob Davidson - PVY epidemic started in mid-90s with increase in Norkotahs and resulted in a community disease. Epidemic has been difficult to get under control. Colorado has passed seed act, hopeful that it will reduce PVY. PHT plots received frost at Yuma, AZ three times this year and did not regrow after last frost. CO rules allow fallback on summer results if Winter results not available. Some leaf testing had already been performed on lots going to Idaho for recertification. Next year CO will pick leaves on latent varieties and test in the lab. Have looked into GH test; cost would be ~2X what it would be in the field. Jeff McMorran - $135 for 400 tuber sample in GH in Oregon; visual assessment only. Jeff does not think they are missing on latent varieties because mosaic symptoms show up well in GH. Mathuresh Singh from Canada indicated that they may miss some N:O positives on visual in GH compared to serological.

Idaho: Doug Boze distributed summary of plot readings since 2004. Seed acreage relatively stable and tied to commercial acreage. Initiated 100% leaf testing in PHT in 2007 for PVY and PVA. They still visually inspect all plots for leafroll. Better planting decisions due to ELISA data have led to a significant reduction in percentage of samples infected with PVY, and a dramatic reduction in the percentage of lots ineligible since started ELISA testing in PHT. Started collecting leaves in first week in January on plants that had emerged and every other week after that. Had frost the first week of February. Most of those plants that were slower to emerge werent as affected by the frost and they were able to collect enough tissue for mosaic test. Jeff McMorran, can you get a valid test after a frost? Doug, yes we did some leaf picking after the frost and put them at the front of the queue in the lab. Rob Davidson, how are growers paying for ELISA? Doug, winter test are included in acreage fee. Fees increased ~$1/acre. Prior to this, picked 100 random leaves out of latent varieties. Growers have accepted the extra testing and are making decisions that are reducing overall virus. Doug has observed that rouging for visual plants may selects for latent strains. Rob Davison, traditional rouging may end up with even endgame; rogue 1, spread 1. Phil Hamm, nowhere in the scientific literature does it say that PVY can be spread mechanically in replicated trials. Mathuresh Singh, has found leaf roll in volunteers in past, now leaf roll gone, but volunteers with PVY can be a problem in New Brunswick. Phil Nolte, first year volunteers are very deep in the soil. In each successive year the tubers produced are higher in the soil profile and more likely to freeze. Idaho doing strain ID on early generation lots with PVY. If problem strains are found, ISU and ICI extension will strongly recommend that the grower eliminate that lot from his production. Phil Nolte, Rangers and Alturas are varieties that select for strains other than O.

California: Pablo Guzman reported that acreage was down 20%. For the 2010 crop, just 1 seedlot was rejected. In one lot, there was no virus in first inspection, and second inspection there was 2-3% PVY. For the 2011 crop, they are behind on planting with most of the crop planted in January rather than December due to rain. Should be back to 700 acres in 2011. Most of seed stays in California, little export out of state. There are three growers in the program located in Stockton, Bakersfield, and Tooley Lake growing primarily fresh market varieties. Do not grow any lots for recertification. Bring lots in from other states. Just produce one generation as seed before it goes for commercial seed. Rarely do recertification for their own farm. If they want to recertify, PHT results based on random 400 plant samples within the field at the end of the growing season.

Montana: Nina Zidack reported that overall PVY levels are similar to the last few years. There were some significant current season increases in Norkotah CO3 from summer testing to the PHT. Rob Davison suggested growers reduce fertilizer and make sure you get good vine kill. Jonathon Whitworth commented that in his studies, CO3 current season infection rates are significantly higher than standard Norkotahs.

Nebraska: Steve Marquart, were able to read PHT samples before frost in Florida. Only lost two lots. 99.9% of lots passed inspection. There are three seed growers in Nebraska and they have very little virus or no virus.

Washington: Andy Jenson, a grower from Skagit valley is having problems with mosaic type disease with some tuber symptoms. Seed comes from BC and Lindon area. They will plant some of these lots in the seedlot trial at Othello. Mark Pavek is seeing PVY mosaic going down in the commercial seedlot trial. In 2008, 15% of seedlots had severe mosaic. In 2010 only 3% of seedlots had severe mosaic.

Oregon: Jeff McMorran, 2010 was an average year. Down 5,000 acres from high in 2007. Major problems in Klamath area. Seed not isolated as well as it should be. With irrigation issues, commercial acreage encroaching on seed fields resulting in contamination. Diversifying varieties away from traditional processing varieties. An example is Pike, which is a problem with virus. One puzzling problem with Alturas was observed in GH growout. Virus-like symptoms but have not been able to identify any virus. Increased sample size for lots less than 10 acres, require 400 tubers. RDO, who is a major grower in OR, is shifting some of production to NV for a 1 year increase.

Research Extension Reports:
Phil Nolte: Specialty Crops Research Initiative Grant; Led by Stuart Gray.
Grant on developing strategies to manage PVY strains.

Selected objectives:
Continued surveillance and assessment of PVY strains.
Produce training manuals that will assist certification inspectors and growers.
Develop cost-based risk assessment analysis of in-season field inspection vs. post harvest testing methods.
Minituber vs. conventional seed production in the field  impact of virus disease on both systems.
The economics of planting PVY-infected seed.

Effects of seed-borne levels (0-50%) on Yield:
Yield reduced ~75cwt with 50% PVY in Russet Burbank.
Much of yield loss in in US1 profile.
1% PVY; 1.5 cwt loss/acre.

All PVY + strains coming into lab of Phil Nolte - Alex Karasev does typing, monoclonals and PCR (Lorenzen primers)

Mark Pavek: Washington State University.
The Washington Potato Seed Lot Trial has been conducted for 47 years. In 2010, Washington acreage dropped 20% compared to 2007. The largest number of samples in the trial come from Montana which is followed by Idaho, Oregon, Washington, Canada, Colorado, and other states. The main variety is still Russet Burbank, but other varieties are increasing. Ranger is decreasing and Umatilla is steady. The total number of varieties in seedlot trial almost doubled since 2002. Severe Mosaic peaked in 2008 and came down significantly in 2010. No leafroll was detected in 2009 seedlots. For the 2011 seedlot trial, planting will starton March 23. The first reading will be performed June 7 and includes inspector training, and the second reading will be on June 21. The trial field day will be the morning of June 23. Mark invited anyone who is interested to participate in the readings or field day.

Jonathon Whitworth: PTNRD symptoms from PVYo in a controlled environment:
Compare PVYo strains that cause tuber necrotic symptoms at different temperature regimes, 20 and 27C.
Yukon Gold.
Hand inoculation.
Variable light according to plant growth stage.
O Strains T1, ID154, CW.
NTN Strains n4, NY29.
CW, NY29 and N4; PTNRD symptoms in tubers.
Screenhouse, Hermiston, Oregon, T1 produces PTNRD.
Greenhouse, Aberdeen, T1 caused PTNRD in Chippewa.

Steve Marquardt: How might lower nighttime temperatures affect symptom developments? Do temperature fluctuations or stress influence symptoms?

Mathuresh Singh: Director, Agricultural Certification Services, New Brunswick, CA:
Monitoring Current Season Spread of PVY in Seed Potato Fields of New Brunswick.

Research Questions:
Can we measure current season spread of PVY as crop is growing?
Can we test aphids from traps for the presence of PVY?
Can we develop a management tool to help growers in making decision on their crop to top kill/not to top kill?
Can we develop a pre-harvest trest protocol coparable to post-harvest test protocol?

Experimental Varieties:
Cal White,
Gold Rush,
Innovator,
Shepody,
Russet Burbank.

Aphid traps. Water with propylene glycol and soap and Bitrex; hard to maintain ratio due to precipitation and evaporation:
Collect aphids in 2-3 days.
Identified vectors.
Pulled out stylet  12 stylets from same aphids pooled together.
Raspberry aphids Amphorophora agathonica; 44% carrying PVY.
Aphids that normally colonize potatoes are being killed, and those from other hosts are flying in from outside and spreading disease.

Virus Transmission:
Early in season (June 15) PVY positive aphids present, PVY detected in plants 2-3 weeks later.
Grower that sprayed oil every 4-5 days significantly reduced aphids collected.
Protection from Admire; protects against colonizing aphids, does not protect against transient aphids.
Need to start using oil earlier.
Oil should be sprayed on commercial fields also; reduce chance aphids will pick up PVY.

Leaf test vs tuber test, ELISA vs. PCR:
Similar results in leaves, PCR slightly more sensitive in tubers.
September 15 tuber PCR detects more than August 4 PCR.

Field location:
Field next to tree rows (with wild raspberry plants) had more aphids and more PVY.

Why so much current season spread?
We are growing more susceptible and asymptomatic varieties.
More inoculum than ever/new strains.
Winters are milder resulting in more volunteers and early influx of non-potato aphids (frequent flyers).
More emphasis on aphid control than inoculums.
Change in management practices are not fast enough (oil vs. insecticide).

Summary:
Spread started to take place very early; protect crop early in season.
Can we measure current season; yes.
In most varieties tuber test detected higher amount of PVY than leaf test. Therefore tuber test would be more reliable as preharvest test.

Sahar Eid: University of Idaho.
Role of the 17-kDa protein (P4) in potato leafroll virus transmisioon by aphids Myzus persicae.
Background on PLRV: Not transmitted mechanically, transmitted efficiently by Myzus persicae, upward roll of foliage,net necrosis, P4 required for movement of PLRV role in aphid transmission.

Preliminary data:
WT is up to 96% transmission efficiency, while P4 nul is 0% transmission efficiency.
pBNUP110 (binary vector harboring PLRV complete genome).

Point mutations using quickChange II Site-Directed Mutagenesis kit.

Determine sites of mutation - Multiple sequence alignment by clustal X 2.0:
Mutagenic primers design using web based QuikChnge Primer Design Program.
Agrobacterium infiltration of Ni. Benthaniana with LBA4404 strains carrying pBNUP110R mutated P4.

Reveal possible role of P4 in aphid transmission:
Distribution pattern of the virus in the plant.
Physical association with virion.

Jordon Eggers: Oregon State University, Hermiston; PVY screenhouse trial - third year.
Objectives:
Determine the foliar and tuber symptoms in eight different cultivars in seed infected with 3 strains of PVY, evaluate tuber and foliar symptoms, determine yield impact of tuber borne infection.

In 2009, 8 cultivars and 6 strains, 2 NTN, 2O, and 2 N:O.

In 2010, used seed infected seed from 2009 experiment. Planted healthy controls.

ELISA testing on June 10, positive plants identified with yellow flags.

Results:
Emergence -
Alturas, Yukon Gold infected with some strains didnt come up.
Across all cultivars, N:O strains had the most significant impact on emergence;
Alturas and Yukon gold more severely affected.
Yukon Gem and Premier had less %PVY infection (have PVY resistance).
T3V2(NTN) and CO35(O) plants had less infection; delayed transmission to tubers?
NTN isolate T3V2 has less visual symptoms, AL1(N:O) also less severe symptoms;
Foliar mosaic symptom severity, Premier, Norkota and Yukon Gem are least severe, Blazers can be infected, but dont show severe mosaic.

Symptoms: foliar N strains have more of a blotchy mosaic.

Symptoms for tubers:
Distinct differences between cultivars and how they respond to different strains; range from no tuber symptoms through external rings to internal necrosis.
Yukon Gem, Yukon Gold had higher tuber symptoms.
Alturas also severe - no tubers from AL1(N:P) and OR2(N:O).

Yield: Reduced especially in Yukon Gold and Russet Burbank.

Conclusions:
Not all strains produce the same foliage or tuber symptoms and have the same impact on yield.
The same PVY strain may not produce the same foliage or tuber symptoms and have the same impact on yield.
Potato cultivars resistant to PVYO apparently not resistant to N:O.

Chet Setula: Wondering if there may be other viruses in strains caused atypical symptoms - recommended sending samples to Keith Perry to run solanaceous macroarray; 150 viruses.

Alexander Karasev - New PVY Recombinant types:
Found in Brazil, composed of NTN and NE-11 genomes, exhibit unusual serology, overcome all known PVY resistance genes, can be mistaken for ordinary NTN-strain, may enter the US so surveillance is needed, PVY-AST isolate is an (almost) ordinary PVY-NTN, two isolates, PVY-AGA and PVY-MON represent new type of PVY recombinants, never seen before.

Reactions in potato indicators: AST; Local and systemic HR, system vein necrosis, mosaic, crinkling in upper leaves. Isolates MON and AGA; no local or systemic HR, no vein necrosis, mild symptoms.

PTNRD in Yukon Gold -Typical symptoms in Yukon gold: Induce PTNRD in susceptible cultivars,
overcome all known resistance genes, may induce only mosaic in tobacco, may be missed if diagnosed by certain monoclonal antibodies, need special attention from quarantine standpoint.

Mathuresh Singh: Brazil has 2% tolerance for PVY:
PVY-O5, name coined by Peter Ellis, a group of PVY-O strains reactive against 1F5 monoclonal antibody, initially described only 2 isolates, thought to be rare, misidentified as necrotic PVY-N.

Typical O by tobacco veinal necrosis (-), multiplex PCR.
Looks like PVY-O with a single substitution in coat protein.
All but 1 of PVY-O5 isolates cluster in a single phyllogenetic lineage.
Not all PVY-O strains equal PVY-05 different in other ways, not just serology.
More severe on cv. Desiree.

Where did the recombinants come from? Possibilities:
PVY recombines all the time due to the different strains present
Recombination rare?
Origin is polyphyletic.
N:O and N-Wi originated independently.
N:O is a pre-cursor of NTN.
Recombination of PVY is rare?

Tomato Spotted wilt:
Jonathan, in 1st generation in GH breeding program then self eliminating.
Jim Crosslin, has not had a sample with necrotic rings positive for TSWV in quite a while.

Mop Top:
Jim Crosslin: published paper on ND Mop Top; in 5 states.
Phil Nolte: 12% mop top on one field of RB at RDO.
Emerging disease.

Joe Munyaneza: Zebra chip disease, Liberibacter, and potato psyllid.
Documented in SW US, Mexico and Central America.
First Identified in Mexico in 1994, and US in 2000.
Recently documented in New Zealand.
Causing millions of dollars in losses to potato industry.

Symptoms:
Looks like leaf roll or purple top.
Chlorosis develops over time.
Internodes shorten.
Purple or yellow pigmentation.
Leaf scorching.
Wilts and dies.
Causes pink eyes, (collapsed) stolons.
Striping discoloration internal in tuber.

Vector for Potato Psyllid (2006):
2008: Scientists in NZ and UC-Riverside established association of ZC with Candidatus liberibacter solanacearum or psyllaurous.
The new bacterium is related to, but different from Liberibacter which causes citrus greening disease.
Affects other solanaceous plants.

Resistant varieties to ZC? Variety screening under controlled field cage conditions:
10 varieties screened - no varieties in initial trial are resistant to ZC.
2010 - 105 varieties advanced breeding lines:
20 lib-infective psyllids/plant@bloom stage; insects eliminated with insecticides after 2 weeks.
Plants observed for ZC symptoms.
Atlantic is very susceptible; 1 plant placed in cage with each variety.
23 lines with light ZC symptoms in raw tubers; had severe symptoms when fried, no symptoms when baked
6 lines with almost no visible ZC symptoms in tubers.
73 lines very susceptible to ZC.
Some varieties (4) had no symptoms when compared to Atlantic control; No symptoms in fried trips.

Impact of Psyllid on seed quality (Liberibacter vs. Psyllid yellows):
Plants produced by ZC affected tubers do no significantly contribute to ZC incidence.
Observational data in Mexico and NZ that ZC affected tubers constitute a major factor for ZC spread, but no scientific data is available to back up this claim.
We designed a field cage experiment to gain more information on this issue.
Most tubers never sprout.

Experiment:
Liberibacter + Psyllids,
Liberibacter alone,
Psyllids alone,
healthy control.

Two Varieties, Ranger and Atlantic.

Planted in cages:
ZC infected tubers never came up.
Tubers from Psyllid yellows gave rise to healthy plants, similar to healthy controls.
Liberibacter-affected seed, no emergence or extremely stunted, eventually produced healthy. Plants, very poor emergence - ~10%, 30 days delayed emergence, no Rangers came up.

Conclusions:
ZC seriously affects seed quality, no sprouting, hair sprouts and weak plants.
Psyllid yellows does not appear to affect seed germination or normal plant growth.
Production of ZC plants appears non-significant in spread of disease.
Results in disagreement with observations/reports from Mexico and New Zealand.
Late ZC infections may carry infection to next year, going to do experiments this year in WA.
Data could be important in terms of international trade.

L. solanacearum and non-solanaceous crops Scandinavia :
Carrot Psyllid, thought it may have toxin which causes red pigmentation.
Did not detect phytoplasmas.
Carrots infected with same liberibacter causing ZC in potato.
First report of Liberibacter in Europe.
First report in non solanaceous species.
Recently detected in carrots in Spain and Canary Islands.
Potato Psyllid on carrot?
Does not reproduce on carrots, but will live for 3-4 weeks.
Infected a few plants.
Using electrical waveform analysis, does not feed on phloem.
Psyllids are host specific.

Liberibacter in Pear:
Candidatus Liberibacter europaeus - transmitted by the pear psyllid in Italy.
Behaves as an endophyte rather than a pathogen? Only maintained for 6 months, may develop disease symptoms after more time.

March 11, 2011

Jeff announced we may be eligible for a rebate from the hotel. He will e-mail us with the details if it is worth distributing to the attendees.

Psyllids:
Rob Davison: Psyllid populations may be showing resistance to insecticides in CO. They had damaging problems late in the season, even in the San Luis valley. They were also found in Nebraska and North Dakota. Joe says the insects tend to move when it gets very hot; above 35C, symptoms also never develop at this temperature. Jim Crosslin will be testing Psyllids from multiple states. In 2010, tested 8000 psyllids, ~1% were liberibacter positive. Joe, Psyllids are being trapped in the Rio Grande Valley and are present there now. Will be moving North. Goolsbie in Texas does the trapping. You can get on a list to be notified of where the Psyllid is being found. For name of website need to ask Joe.
Two sources of Psyllids, Texas or California, currently biotyping. Identifying haplotypes. California similar to New Zealand. Washington is similar to Texas haplotype. Nebraska seems to be a mixed population. In Texas, farmers never had to spray for Psyllids; now they have to spray weekly. Joe thinks Psyllids were there before, but that the Liberibacter was not present, so ZC wasnt ever established. Joe says you need early detection of Psyllids to get control. If you wait to see symptoms of Psyllid yellows, it is too late to apply insecticides. This may explain why people have said that they are getting poor control with insecticides. As Psyllids move North, they seem to lose Liberobacter. Jim Crosslin, there are spray records for Frito Lay sites where Psyllids were trapped. Pyrethrin insecticides result in increase of Psyllid populations. Jim reported that Weslaco station will be closed in 2012 so they will lose those research sites. Joe thinks NW is not currently threatened by ZC because Psyllid population does not have liberobacter. Discussion commenced on how this might be influenced by changes in the climate. Jeff Bradshaw in Nebraska is putting tall towers (25m) for trapping insects.

Tobacco Rattle Virus:
Jim Crosslin: a few positive samples from CO.

Mop Top:
Phil Hamm: Discussed bait testing technique; grow tobacco in suspect soil, get powdery scab, then isolate virus. Rarely or never see foliar symptoms. Sample from WI  wetter and cooler, substantial damage from powdery scab. Also, problematic in ND this year. Jim Crosslin, NA and European isolates of Mop Top genetically very similar; points to a recent introduction from Europe.

Emerging Disease Issues:
Phil Hamm: Virus-like symptoms in Alturas from OR seed grower. Distortion, necrosis, vein burning. Tested positive for PVS. Samples of seedlot growing in GH, negative Y,A,X,M. Transplanted from PHT to another GH, still showing symptoms. Steve suggested using broad Poty test.

Jim Crosslin: 4-5th year, classic purple top symptomatic plants came into lab, negative for BLTVA, no graph transmission. Phil asked if there was Rhizoctonia associated. Shortened internodes, intense purpling, rolling of leaves, no aerial tubers. Jonathon suggested it may be a number of things that disrupt vascular transport. Phil said they looked like true purple top.

Pablo: Cal white coming Alberta positive for BLTVA; present on early inspection

Toxic seed piece syndrome: Seed piece gets glassy, translucent appearance. Wilted, drooping plant
Phil Hamm: Tri-state funded project to start tracking PVY strains in seedlots

Business Meeting:
PVY pictures on website potatovirus.com, Jonathon Whitworth, pictures still being posted. If you have pictures, send them to Phil Nolte or Jonathon. Send samples (Plant Saver Cards) with pictures and send to Jonathon

Renewal of WERA project completed. Compiled all of info and put it on NIMSS page. Discussed eligibility for WERA award. Phil Nolte will pursue getting an application for our group. Hamm, this would be recognition that the group is doing something important. Get forms off of NIMSS site. Contact Donn Thill or Holly Waters to get info on how to file application.

Video: Grow profits, not problems:
(look at last years minutes),
Stewart Grays presentation satisfies this,
look for video on potatovirus.com.

PVY Management Plan:
Nothing more needed.
From PAA meeting - Management plan needs to be decoupled from MOU.
Rob: John Keeling indicated that it was a federal plan and we had to follow it.

Impact Statements for 2010:
What was done last year?
Jeff read statements from last year.
Joe will collect statements for this year.
Rob Davidson, characterization of new strains of PVY. Karasev, impact of tuber-borne infection different strains of PVY on different cultivars. Hamm, preliminary data from Munyaneza Seed-borne transmission is not important for Zebra Chip

Information on PVY antisera for NAPPO:
Export standards.
Stewart supposed to develop a bullet point paper with technical details for NAPPO panel to make decisions on testing requirements for export.

Elections for Secretary:
Joe Munyaneza nominated Alex Karasev; unanimously elected and will serve as Secretary in 2012

Meeting for next year:
San Antonio suggested.
If we did it in April, we could visit Joe Munyanezas plots for ZC
2nd week of March preferred, could still do potato field trip.

Narceo: showed materials from BioReba.

Adjourned at 10:45 AM

Accomplishments

The Outstanding Paper of the year Award (OPA) was granted by the Potato Association of America to:<br /> <br /> Serological Properties of Ordinary and Necrotic Isolates of Potato virus Y: A Case Study of PVYN Misidentification <br /> <br /> Alexander V. Karasev, Olga V. Nikolaeva, Xiaojun Hu, Zachary Sielaff, Jonathan Whitworth, James H. Lorenzen and Stewart M. Gray<br /> <br /> This paper is available via Springer at the following link:<br /> <br /> http://www.springerlink.de/content/04u8141225868w72/fulltext.pdf<br />

Publications

Brown, C.R., K.G. Haynes, M. Moore, M.J. Pavek, D.C. Hane, S.L. Love, R.G. Novy, and J.C. Miller Jr. 2010. Stability and Broad-Sense Heritability of Mineral Content in Potato: Iron. Am. J. Potato Res 87:390-396.<br /> <br /> Buchman, J.L., T.W. Fisher, and J.E. Munyaneza. 2011. Zebra chip disease development over time. Proceedings of the 2010 Annual Zebra Chip Meeting, Dallas, TX (November 2010) (in press). <br /> <br /> Buchman, J.L., V.G. Sengoda, and J.E. Munyaneza. 2011. Potato psyllid density and feeding duration required to cause zebra chip. Proceedings of the 2010 Annual Zebra Chip Meeting, Dallas, TX (November 2010) (in press). <br /> <br /> Crosslin, J.M., J.A. Goolsby, and J.E. Munyaneza. 2011. Incidence of Candidatus Liberibacter solanacearum in potato psyllids collected in the south-central United States in 2010. Proceedings of the 2010 Annual Zebra Chip Meeting, Dallas, TX (November 2010) (in press).<br /> <br /> Crosslin, J.M. and L.L. Hamlin. 2010. First report of Impatiens necrotic spot virus infecting greenhouse-grown potatoes in Washington State. Plant Dis. 94:1507.<br /> <br /> Crosslin, J.M., and L.L. Hamlin. 2011. Standardized RT-PCR conditions for detection and identification of eleven viruses of potato and potato spindle tuber viroid. Am. J. Pot. Res. (in press).<br /> <br /> David, N., I. Mallik, J.M. Crosslin, and N.C. Gudmestad. 2010. First report of Potato mop-top virus on potatoes in North Dakota. Plant Dis. 94:1506.<br /> <br /> Ember, I, Z. Acs, J.E. Munyaneza, J.M. Crosslin, and M. Kolber. 2011.<br /> Survey and molecular detection of phytoplasmas associated with potato in Romania and southern Russia. European Journal of Plant Pathology (in press).<br /> <br /> Goolsby, JA., J. Adamczyk, JM. Crosslin, JE. Munyaneza, N. Troxclair, J. Anciso, R. Villaneuva, P. Porter, E. Bynum, C. Rush, F. Workneh, D. Henne, C. Nansen, P. Sloderbeck, A. Joshi, L. Buschmann, J. Bradshaw, B. Lee, B. Zechmann, and G. Bester. 2011. Regional monitoring of potato psyllid populations and the associated pathogen, Ca. Liberibacter psyllaurous. Proceedings of the 2010 Annual Zebra Chip Meeting, Dallas, TX (November 2010) (in press).<br /> <br /> Gray, S.M., DeBoer, S.H., Lorenzen, J., Karasev, A.V., Whitworth, J., Nolte, P., Singh, R.P., Boucher, A., and Xu, H. (2010) Potato virus Y: a significant and evolving threat to potato crops in the United States and Canada  Feature Article. Plant Disease 94: 1384-1397.<br /> <br /> Greenway G.A., J.F. Guenthner, L.D. Makus, and M.J. Pavek. 2010. An Analysis of Organic Potato Demand in the U.S. Am. J. Potato Res. (In-press, online) DOI 10.1007/s12230-010-9180-1.<br /> <br /> Greenway, G.A., J.F. Guenthner, L.D. Makus, and M.J. Pavek. 2010. Fresh Potato and Meat Preferences by U.S. Region. J of Food Distribution Res 41(2): 12-25.<br /> <br /> Karasev, A.V., X. Hu, C. Kerlan, O.V. Nikolaeva, J.M. Crosslin, and S.M.<br /> Gray. 2011. Genetic diversity of Potato virus Y-O and origin of recombinant PVY strains. Phytopathology (in press).<br /> <br /> Karasev, A.V., Nikolaeva, O.V., Hu, X., Sielaff, Z., Whitworth, J., Lorenzen, J.H., and Gray, S.M. (2010). Serological properties of ordinary and necrotic isolates of Potato virus Y: a case study of PVYN misidentification. Amer. J. Potato Res. 87: 1-9.<br /> <br /> Lacey, LA, TX Liu, JL Buchman, JE Munyaneza, JA Goolsby, and D. R. Horton. 2011. Entomopathogenic Fungi (Hypocreales) for Control of Potato Psyllid, Bactericera cockerelli (`ulc) (Hemiptera: Triozidae) in an Area Endemic for Zebra Chip Disease of Potato. Biological Control 56: 271-278.<br /> <br /> Munyaneza, J.E. 2010. Psyllids as vectors of emerging bacterial diseases of annual crops. Southwestern Entomologist 35: 417-477.<br /> <br /> Munyaneza, J.E. 2010. Emerging leafhopper-transmitted phytoplasma diseases of potato. Southwestern Entomologist 35: 451-455.<br /> <br /> Munyaneza, J.E., T.W. Fisher, V.G. Sengoda, S.F. Garczynski, A. Nissinen, and A. Lemmetty. 2010. Association of "Candidatus Liberibacter solanacearum" with the psyllid Trioza apicalis (Hemiptera: Triozidae) in Europe. Journal of Economic Entomology 103: 1060-1070.<br /> <br /> Munyaneza, J.E., Buchman, J.L., Sengoda, V.G., Fisher, T.W., Bester, G., Hoopes, R., Miller, C., Novy, R., Van Hest, P., and J. Nordgaard. 2011. Potato variety screening trial for zebra chip resistance under controlled field cage conditions. Proceedings of the 2010 Annual Zebra Chip Meeting, Dallas, TX (November 2010) (in press).<br /> <br /> Munyaneza, J.E., Buchman, J.L., Goolsby, J.A., Ochoa A.P., and G. Schuster. 2011. Impact of potato planting timing on zebra chip incidence in Texas. Proceedings of the 2010 Annual Zebra Chip Meeting, Dallas, TX (November 2010) (in press).<br /> <br /> Munyaneza, J.E., A. Lemmetty, A.I. Nissinen, V.G. Sengoda, and T.W. Fisher. 2011. Molecular detection of both aster yellows phytoplasma and Candidatus Liberibacter solanacearum in carrots affected by the psyllid Trioza apicalis (Hemiptera: Triozidae) in Finland. Journal of Plant Pathology (in press). <br /> <br /> Nelson, WR, TW Fisher, and JE Munyaneza. 2011. Haplotypes of Candidatus Liberibacter solanacearum suggest long-standing separation. European Journal of Plant Pathology 130: 5-12.<br /> <br /> Nolte, P. Seasons Briefings: What's new with PVY? Proceedings of the University of Idaho Winter Commodity Schools 2010.<br /> <br /> Novy R.G., J.L. Whitworth, J.C. Stark, S.L. Love, D.L. Corsini, J.J. Pavek, M.I. Vales, S.R. James, D.C. Hane, C.C. Shock, B.A. Charlton, C.R. Brown, N.R. Knowles, M.J. Pavek*, T.L. Brandt, S. Gupta, N. Olsen. 2010. Clearwater Russet: A Dual-Purpose Potato Cultivar with Cold Sweetening Resistance, High Protein Content and Low Incidence of External Defects and Sugar Ends. Am J Potato Res 87:458-471.<br /> <br /> Novy, R.G., Whitworth, J., Alvarez, J., Trumble, J.T., Butler, C., Buchman, J.L., and J.E. Munyaneza. 2011. Unique tri-species germplasm with multiple insect resistances and its use in breeding for resistance to psyllid/zebra chip. Proceedings of the 2010 Annual Zebra Chip Meeting, Dallas, TX (November 2010) (in press).<br /> <br /> Pantoja, A., Hagerty, A.M., Emmert, S.Y., and J.E. Munyaneza. 2010. Leafhoppers and potatoes in Alaska. Agroborealis 41(1): 28-33.<br /> <br /> Pearson, C.C., E.A. Backus, and J.E. Munyaneza. 2011. Feeding biology of the potato psyllid, Bactericera cockerelli. Proceedings of the 2010 Annual Zebra Chip Meeting, Dallas, TX (November 2010) (in press). <br /> <br /> Peng, L., J.T. Trumble, J.E. Munyaneza and T.-X. Liu. 2011. Repellency of a kaolin particle film to potato psyllid, Bactericera cockerelli (Hemiptera: Psyllidae), on tomato under laboratory and field conditions. Pest Management Science. Online, http://onlinelibrary.wiley.com/doi/10.1002/ps.2118/pdf.<br /> <br /> Robles-Hernández, L., González-Franco A.C., Hernández-Huerta, J., Meacham, T.M., Nikolaeva, O.V., and Karasev, A.V. 2010. First identification of an unusual recombinant Potato virus Y strain in potato in Mexico. Plant Disease 94: 1262. <br /> <br /> Stark, J.C., R.G. Novy, J. L.Whitworth, N.R. Knowles, M.J. Pavek*, S.L. Love ,M.I. Vales, S.R. James, D.C. Hane, C.R. Brown, B.A. Charlton, D.L. Corsini, J.J. Pavek, N. Olsen and T. Brandt. 2010. Classic Russet: A Potato Cultivar with Excellent Fresh Market Characteristics and High Yields of U.S. No. 1 Tubers Suitable for Early Harvest or Full-Season Production. Am. J. Potato Res. 87:360-373.<br /> <br /> Whitworth, J.L., R.G Novy, J.C. Stark, J.J. Pavek, D.L. Corsini, S.L. Love, J.S. Miller, M.I. Vales, A.R. Mosley, S. Yilma, S.R. James, D.C. Hane, B.A. Charlton, C.R. Brown, N.R. Knowles, and M.J. Pavek. 2010. Yukon Gem: A Yellow-Fleshed Potato Cultivar Suitable for Fresh-Pack and Processing with Resistances to PVYO and Late Blight Am J Potato Res 87:327336.<br /> <br /> Whitworth, J., P. Hamm, and C. McIntosh. 2010. Effect of Potato Virus Y on Yield of a Clonal Selection of Russet Norkotah. American Journal of Potato Research 87: 310-314.<br /> <br /> Whitworth J., R.Novy, J.C.Stark, J.J.Pavek, D.L.Corsini, S.L.Love, N.Olsen, S.Gupta, T.L.Brandt, M.I.Vales, A.R.Mosley, S.Yilma, S.R.James, D.C.Hane, B.A.Charlton, C.C.Shock, N.R.Knowles, M.J.Pavek, J.S.Miller, C.R.Brown. 2011. Alpine Russet: A potato cultivar having long term tuber dormancy making it suitable for processing from long-term storage. Am J Potato Res (in-press).<br /> <br /> Yang, X.-B., Zhang, Y.-M., Hau, L., Peng, L.-N., J.E. Munyaneza and T.-X. Liu. 2010. Repellency of selected biorational insecticides to potato psyllid, Bactericera cockerelli (Hemiptera: Psyllidae). Crop Protection 29: 1329-1324. <br /> <br /> Posters<br /> <br /> Nolte, P., JM Alvarez and J Whitworth. PVY Management for the Seed Potato Producer. Presented at the National Potato Council Potato Expo. Orlando, FL. January 4-6, 2010.<br /> <br /> Web Page<br /> <br /> Gray, S., A Karasev, J Lorenzen, J Whitworth, P Nolte, R Groves and Amy Charkowski. 2010. The changing face of Potato Virus Y: The science, politics and business of virus management in the US potato Crop. APS Plant Management Network, Focus on Potato Webcast. Web Address Listed Below.<br /> http://www.plantmanagementnetwork.org/edcenter/seminars/Potato/PotatoVirusY/player.html<br />

Impact Statements

1. Characterization of new strains of PVY
2. Assessment of the impact of tuber-borne infection of different strains of PVY on different potato cultivars
3. Assessment of the impact of zebra chip disease and potato psyllids on potato seed quality and disease spread

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