Annual/Termination Reports:

[05/16/2012] [05/15/2013] [10/14/2014] [06/09/2015] [11/04/2016]

Report Information

Participants

Abad, Jorge (jorge.a.abad@aphis.usda.gov) - USDA-APHIS, Beltsville, MD;
Bajet, Narceo (narceoba@eurofinsus.com) - Eurofins STA Laboratories;
Crosslin, Jim (jim.crosslin@ars.usda.gov) - USDA-ARS;
Davidson, Robert (rddavid@ext.colostate.edu) - Colorado State University;
Eggers, Jordan (Jordan.Eggers@oregonstate.edu) - Oregon State University;
French, Allan (Allan.french@simplot.com) - Simplot, Nampa, ID;
Gray, Stewart (smg3@cornell.edu)- USDA-ARS, Ithaca, NY;
Guzman, Pablo (pguzman@ucdavis.edu) - Ca CIA \ UC Davis;
Hamm, Phil (philip.b.hamm@oregonstate.edu) - Oregon State University;
Henne, Donald (DCHenne@ag.tamu.edu) - Texas A&M Univ., Weslaco, TX;
Holcomb, Jesika (sabolj@onid.orst.edu) - Oregon State University;
Jones, Rebecca (rebecca.jones@simplot.com ) - Simplot, Moses Lake, WA;
Karasev, Alex (akarasev@uidaho.edu) - University of Idaho;
Marquardt, Steve (smarquardt@nebraskapotatoes.com) - Nebraska Seed Department;
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;
Prosek, Kimberly (kimberly.prosek@montana.edu) - Montana State University;
Rondon, Silvia (Silvia.Rondon@oregonstate.edu) - Oregon State University;
Salazar, Luis (lsalazar@agdia.com) - Agdia, Elkhart, IN;
Sather, Kent (ksather@lamar.colostate.edu) - Colorado State University;
Schuetz, Keith (kschuetz@agdia.com) - Agdia, Elkhart IN;
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;
Whitworth, Jonathan (jonathan.whitworth@ars.usda.gov) - ARS-USDA, Aberdeen, ID

Brief Summary of Minutes

Joe Munyaneza - Chair
Nina Zidack - Vice-Chair (not present)
Alex Karasev - Secretary

On March 15, 2012, Joe Munyaneza (Chair) opened the meeting at 8:00 am, briefly presented the agenda, and reported that the group administrative advisor, Donn Thill, Director of the Idaho Agricultural Experiment Station, was unable to attend in person, but would be able to connect by phone later. Participants introduced themselves.

Minutes of the 2011 meeting in Tucson, AZ, were moved for approval by the chair, seconded, and approved by unanimous vote.

The agenda started with state reports, following tradition of WERA-89.

Colorado - Kent Sather described the past season as slow starting, with cool weather early in the season, and record year for green peach aphids. Most seed lots rejected were rejected due to PVY, and these mainly Norkotahs and Fingerlings. No Zebra Chip found in San Luis Valley in 2011. Seed test plots in Yuma, AZ, affected by cold weather, results were sent to growers by February 20. Current tag tolerance for CO is 10% for PVY; but 20% of RN lots had levels exceeding 10% PVY. One lot had PLRV, this was an organic seed lot.

Washington - Mark Pavek reviewed the Othello, WA, trials during 2011. Montana currently is the main source of potato seed, with Russet Burbank being the main cultivar planted. However, the share of RB decreases over the years. The number of new cultivars planted keeps going up. Mosaic and blackleg remain steady from 2010. PLRV was not found; PLRV suppression efforts were efficient so far. In the discussion, after the presentation, Mark noted that Norkotahs continue to be the highest source of PVY.

Idaho - Phil Nolte gave an overview of the 2011 winter grow-out results. Idaho had an uptick in the PVY level, the number of seed lots rejected for re-certification increased to the 2009 level. Previously, the rejection rate decreased every year since 2007. This persistent decrease was attributed to the implementation of the mandatory ELISA testing in the winter grow-out, introduced in 2006. Discussion followed to try to explain the reasons for the uptick. Possible reasons mentioned were new varieties, climatic factors, or changes in practices (organic potato). Idaho had its first official Zebra Chip find in 2011, but left details for a later presentation.

Montana - Susie Siemsen reported that no Zebra Chip was found in 2011 in Montana. Montana saw increased levels of PVY in winter grow-out tests relative to summer inspections. She blamed mild fall and slow season's start; hence growers were late with vine kill, which perhaps promoted late aphid flight and late infections not visible on foliage. Applications of insecticides to control PVY do not work.

California - Pablo Guzman reported that he saw ZC in CA (1 grower).

Nebraska - Steve Marquardt reported that NE is doing large scale psyllid testing; last year's population was low but this year they saw an increase in psyllid numbers. They are usually found in the fields the first week of June. Green peach aphids were rarely seen. They saw an increase in PVY, 3-5% in the winter grow-out test.

Oregon - Jordan Eggers reported data from the Oregon winter grow-out. There were 27 OR lots, four lots with mosaic (Shepody and Norkotahs) and two WA seed lots with mosaic.

Canada - Mathuresh Singh presented field research data on controlling PVY spread with mineral oil spray applications. This is a very promising strategy in Canada, but timing of application is very important.

Donn Thill - connected to the meeting via telephone conference - complimented WERA-89 for successful work over the years, informed that WERA-89 was renewed last year and thus has another 4 years to go. Donn also instructed the members on timely submission of impact statements for the group's activities. He reported on the Federal budget situation as it related to potato pathology, including proposed reductions for ARS. In the discussion, Donn explained that the Specialty Crop Research Initiative program will likely continue to be supported through the upcoming Farm Bill. The old Farm Bill will probably be extended for 1 year, until a new one is approved. After Dr. Thill's presentation, state and research reports resumed.

Accomplishments

Alex Karasev - presented 2011 data from the Othello, WA, trials focused on PVY testing and typing. These trials include potato seed coming from several PNW states and Canada. Most of the mosaic samples (ca. 90%) were PVY-positive. Typing of these PVY samples suggested clustering of the isolates from recombinant strains to specific cultivars and producers. Recombinant, NTN isolates were found in seed potato from WA, OR, ID, and MT, as well as in seed from Canada. Similar typing was conducted with Phil Hamm at Hermiston, OR; trial samples gave similar results. <br /> <br /> Stewart Gray gave an overview of the PVY strain composition across all states, and changes over time. In 2004-2006, a national survey was conducted. At that time, a substantial proportion of NTN was found in only one state. Since 2009, select states were surveyed through the SCRI surveys. NTN showed up in more and more states and in more seed lots every year. N:O type seems to be replacing O type. Summer inspections are not very efficient due to late season infections that do not induce foliar symptoms. Winter grow-out test is a real measure of what is present at harvest time. Discussion ensued on possible strategies to control NTN types; one way would be to identify and remove NTN-infected lots from seed production. <br /> <br /> Jonathan Whitworth described experiments on the correlation between visual symptom expression and actual PVY infection determined by ELISA. Experiments were conducted during the Idaho winter grow-out testing this past winter. It is difficult to correlate when ELISA signals are low. <br /> <br /> The second half of the day was focused on discussion of Zebra Chip disease and new areas affected by ZC in 2011. <br /> <br /> Joe Munyaneza gave a historical overview of the ZC emergence in Mexico in early 1990s, gradually spreading to Texas and further north and west. Joe described symptoms of the disease, pathogenesis, vector (psyllid), and effect on tuber yield and quality. Overall, it is a devastating disease with a huge loss potential for the potato industry. He specifically talked about possible effects on potato seed production. The conclusion is that ZC is not at the moment a threat to the seed production, since infected plants do not normally produce viable tubers, and if a tuber sprouts and a plant emerges, it is not infected. This finding contradicts data from New Zealand, but perhaps the reason is over-reliance of New Zealand researchers on real time PCR. Joe described the 2011 ZC outbreak in Washington. Only select spots were affected, 40 miles apart, locations had or did not have ZC in similar potato fields. Origin of infected psyllids is not known, but it is unlikely that it is from Texas. Psyllids may be able to overwinter in Idaho, experiments are ongoing. <br /> <br /> Phil Hamm reviewed the 2011 outbreak of ZC in Oregon and Washington. Initial infected psyllids probably arrived June 20-25, 2011, but first foliar symptoms were noticed in mid-July. First tuber symptoms were reported the week of August 22. Phil showed infrared pictures of the affected circles, at different dates, demonstrating disease spread from a few initial infection foci. He discussed if this problem happened because of a long, no insecticide treatment period. During the discussion it was brought up that some insecticides, pyrethroids, may actually excite psyllids and promote ZC spread. Phil described effect of ZC on variety trial plots, with some cultivars surviving the infection. Also, he reported on finding ZC in gardens around Hermiston, in tomato, tomatillo, and peppers. Lessons for 2012: Spraying, management of volunteers, and monitoring for symptomatic plants. <br /> <br /> Silvia Rondon described studies on ZC conducted at the Hermiston station. Experiments on potential overwintering hosts for psyllids showed that bittersweet nightshade is an overwintering host; other weeds may potentially serve for overwintering as well. Experiments are in progress on testing all these weeds for Liberibacter. Silvia talked about methods to monitor psyllids in the field, and about appropriate chemicals for psyllid control. <br /> <br /> Don Henne described the situation with ZC in Texas. In Texas, he never sees ZC symptoms before bloom. ZC shows up in clusters, edges are affected much more. He discussed how to monitor psyllids; no good recommendation/device so far. Pyrethroids are not used for psyllid control due to the "flare-up" effect on insects. Early season management is crucial to minimize damage. <br />

Publications

Buchman JL, Sengoda VG & Munyaneza JE. 2011. Vector transmission efficiency of liberibacter by Bactericera cockerelli (Hemiptera: Triozidae) in zebra chip potato disease: effects of psyllid life stage and inoculation access period. Journal of Economic Entomology 104: 1486-1495.<br /> <br /> Buchman JL, Heilman BE & Munyaneza JE. 2011. Effects of Bactericera cockerelli (Hemiptera: Triozidae) density on zebra chip potato disease incidence, potato yield, and tuber processing quality. Journal of Economic Entomology 104: 1783-1792.<br /> <br /> Buchman, JL, TW Fisher, VG Sengoda, and JE Munyaneza. 2012. Zebra chip progression: from inoculation to potato plants with liberibacter to development of disease symptoms in tubers. American Journal of Potato Research 89: 159-168.<br /> <br /> Cilia, M., C. Tamborindeguy, T. Fish, K. Howe, T. W. Thannhauser, and S. Gray, 2011. Genetics Coupled to Quantitative Intact Proteomics Links Heritable Aphid and Endosymbiont Protein Expression to Circulative Polerovirus Transmission. J. Virol., 85: 2148 - 2166.<br /> <br /> Cilia, M., Howe, K., Fish, T., Smith, D., Mahoney, J., Tamborindeguy, C., Burd, J., Thannhauser, T., and Gray, S. M. 2011. Biomarker discovery from the top down: Protein biomarkers for efficient virus transmission by insects (Homoptera: Aphididae) discovered by coupling genetics and 2-D DIGE. Proteomics 11:2440-2458.<br /> <br /> Crosslin, J.M., P.B. Hamm, J.E. Eggers, S.I. Rondon, V.G. Sengoda, and J.E. Munyaneza. 2012. First report of zebra chip disease and "Candidatus Liberibacter solanacearum" on potatoes in Oregon and Washington State. Plant Dis. 96:452.<br /> <br /> Crosslin, J.M., S.I. Rondon, and P.B. Hamm. 2012. Population dynamics of the beet leafhopper in northeastern Oregon and incidence of the beet leafhopper-transmitted virescence agent phytoplasma. Am. J. Pot. Res. 89:82-88.<br /> <br /> Crosslin, J.M., N. Olsen, and P. Nolte. 2012. First report of zebra chip disease and "Candidatus Liberibacter solanacearum" on potatoes in Idaho. Plant Dis. 96:453.<br /> <br /> Crosslin, J.M. 2011. First report of Potato mop-top virus on potatoes in Washington State. Plant Dis. 95:1483.<br /> <br /> Crosslin, J.M., L.L. Hamlin, J.L. Buchman, and J.E. Munyaneza. 2011. Transmission of potato purple top phytoplasma to potato tubers and daughter plants. Am. J. Pot. Res. 88:339-345.<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. 88:333-338.<br /> <br /> Crosslin, J.M., H. Lin, and J.E. Munyaneza. 2011. Detection of 'Candidatus Liberibacter solanacearum' in potato psyllids, Bactericera cockerelli Sulc, by conventional and real-time PCR. Southwest. Entomol. 36:125-135.<br /> <br /> Karasev, A.V., Hu, X., Brown, C.J., Kerlan, C., Nikolaeva, O.V., Crosslin, J.M., and Gray, S.M. 2011. Genetic diversity of the ordinary strain of Potato virus Y (PVY) and origin of recombinant PVY strains.<br /> Phytopathology 101: 778-785.<br /> <br /> Kerlan, C., Nikolaeva, O., Hu, X., Meacham, T., Gray, S., and Karasev, A. 2011. Identification of the molecular make-up of the Potato virus Y strain PVYZ. Phytopathology 101:1052-1060.<br /> <br /> Cavatorta, J., Perez, K., Gray, S., Van Ek, J., Yeam, I., and Jahn, M. 2011. Engineering virus resistance using a modified potato gene. Plant Biotech. J. 9:1014-1021.<br /> <br /> Galvino-Costa, S.B., Figueira, A., Camargos, V.V., Geraldino, P.S., Hu, X., Nikolaeva, O.V., Kerlan, C., and Karasev, A.V. 2012. A novel type of Potato virus Y recombinant genome, determined for the genetic strain PVYE. Plant Pathology 61: 388-398.<br /> <br /> Ibolya, E., Z. Acs, J.E. Munyaneza, J.M. Crosslin, and M. Kolber. 2011. Survey and molecular detection of phytoplasmas associated with potato in Romania and Southern Russia. European Journal of Plant Pathology 130: 367-377.<br /> <br /> Ju, H.J., Van Eck, J., and Gray, S.M. 2011. Factors influencing plant regeneration from seedling explants of Hairy Nightshade (Solanum sarrachoides). Plant Cell Tiss Organ Cult. 108:121-128.<br /> <br /> Mello, A.F.S., Olarte, R.A., Gray, S.M., and Perry, K.L. 2011. Transmission efficiency of Potato virus Y strains PVYO and PVYN-Wi by five aphid species. Plant Dis. 95:1279-1283.<br /> <br /> Lacey, L.A., T.X. Liu, J.L. Buchman, J.E. Munyaneza, J.A. 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 /> Liu Q, C Jianchi, J.E. Munyaneza, and E.L. Civerolo. 2011. Endophytic bacterial in potato tubers affected by zebra chip disease. American Phytopathological Society 101: S108.<br /> <br /> Munyaneza, J.E., A. Lemmetty, A.I. Nissinen, V.G. Sengoda, and T.W. Fisher. 2011. Molecular detection of aster yellows phytoplasma and 'Candidatus Liberibacter solanacearum' in carrots affected by the psyllid Trioza apicalis (Hemiptera: Triozidae) in Finland. Journal of Plant Pathology 93: 697-700.<br /> <br /> Munyaneza JE, Sengoda VG, Buchman JL & Fisher TW. 2012. Effects of temperature on 'Candidatus Liberibacter solanacearum' and zebra chip potato disease symptom development. Plant Disease 96: 18-23.<br /> <br /> Munyaneza JE, Buchman JL, Sengoda VG, Fisher, TW & Pearson CC. 2011. Susceptibility of selected potato varieties to zebra chip potato disease. American Journal of Potato Research 88: 435-440.<br /> <br /> Munyaneza, JE, VG Sengoda, L Sundheim, and R Meadow. 2012. First report of 'Candidatus Liberibacter solanacearum' associated with psyllid-affected carrots in Norway. Plant Disease 96: 454.<br /> <br /> Munyaneza, JE, VG Sengoda, R Stegmark, AK Arvidsson, O Anderbrant, JK Yuvaraj, B Ramert, and A Nissinen. 2012. First report of 'Candidatus Liberibacter solanacearum' associated with psyllid-affected carrots in Sweden. Plant Disease 96: 453.<br /> <br /> Nikolaeva, O.V., Roop, D., Galvino-Costa, S.F.B., Figueira, A.R., Gray, S.M., and Karasev, A.V. 2012. Epitope mapping for monoclonal antibodies recognizing tuber necrotic strains of Potato virus Y. American Journal of Potato Research 89: 121-128. <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 67: 815-824.<br /> <br /> Webpage: <br /> <br /> Grey, S. Charkowski, A., Groves, R., Hutchinson, P., Karasev, A., McIntosh, C., Nolte, P., Whitworth, J. Updated Yearly. Managing Potato Virus Y in Seed Potato Production. http://www.potatovirus.com.<br />

Impact Statements

1. The causal agent of zebra chip, Candidatus Liberibacter was first reported in WA, OR, and ID. Management strategies were developed for potato psyllids to minimize the impact of zebra chip. Chemical strategies were identified that are not effective against ZC. ZC does not display tuber-borne infections and does not spread through the seed system.
2. Changes were implemented to differentiate tuber necrotic strains of PVY by monoclonal antibodies. PVY strains were identified and typed recombinant from post harvest tests from multiple states throughout US.
3. The production of diverse internal tuber symptoms due to infections with potato mop top virus, tobacco rattle virus, and tomato spotted wilt virus was determined. This information will aid diagnosticians, fieldmen, and potato processors in identifying the cause of diseased tubers.

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Report Information

Participants

Abad, Jorge (jorge.a.abad@aphis.usda.gov)  USDA-APHIS, Beltsville, MD;
Assis Filho, Francisco (fassis@agdia.com)  Agdia, Elkhart, IN;
Almeida, Teresa (talmeida@colostate.edu)  Colorado State University;
Bajet, Narceo (narceobajet@eurofinsus.com)  Eurofins STA Laboratories;
Clark, Chris (cclark@agcenter.lsu.edu)  LSU Ag Center;
Crockford, Alex (abcrockford@wisc.edu) - UW Seed Cert.;
Crosslin, Jim (jim.crosslin@ars.usda.gov) - USDA-ARS;
Da Silva, Washington (wsilva1@lsu.edu)  LSU Ag Center;
Davidson, Robert (robert.davidson@ext.colostate.edu) - Colorado State University;
Davis, Jeff (jeffdavis@agcenter.lsu.edu)  LSU Ag Center;
Eggers, Jordan (Jordan.Eggers@oregonstate.edu) - Oregon State University;
French, Allan (Allan.french@simplot.com)  Simplot, Nampa, ID;
Gray, Stewart (smg3@cornell.edu)  USDA-ARS, Ithaca, NY;
Groves, Russ (groves@entomology.wisc.edu)  Univ of Wisconsin;
Guzman, Pablo (pguzman@ucdavis.edu) - Ca CIA \ UC Davis;
Henne, Donald (DCHenne@ag.tamu.edu)  Texas A&M Univ., Weslaco, TX;
Hutchinson, Pamela (phutch@uidaho.edu)  University of Idaho;
Karasev, Alex (akarasev@uidaho.edu) - University of Idaho;
Krey, Karol (karol.krey@wsu.edu)  Washington State University;
Laug, Sherry (slaug@idahocrop.com)  Idaho Crop Improvement Association;
Marquardt, Steve (smarquardt@nebraskapotatoes.com) - Nebraska Seed Certification;
Nolte, Cindy (lucindan@uidaho.edu)  University of Idaho;
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;
Sathovalli, Vidyasagar (vidyasagar@oregonstate.edu)  Oregon State University;
Siemsen, Susie (uplss@montana.edu) - Montana State University;
Spence, Raina (rspence@potatoes.com)  Washington State Potato Commission;
Wenninger, Erik (erikw@uidaho.edu)  University of Idaho;
Whitworth, Jonathan (jonathan.whitworth@ars.usda.gov) - ARS-USDA, Aberdeen, ID;
Wohleb, Carrie (cwohleb@wsu.edu)  Washington State University;
Zidack, Nina (nzidack@montana.edu)  Montana State University;

Brief Summary of Minutes

WERA-89 Meeting: March 14-15, 2013 New Orleans, LA, Omni Hotel

8:11 am Call to order  Nina Zidack

Introductions

2013 attendance list passed around, attached at end of minutes

2012 Minutes: change from 2012, Pablo Guzman wanted to correct that he only heard of Zebra chip in CA, he did not actually see it himself.

Minutes moved and seconded and approved.

State reports:

CO: Kent Sather reported a record aphid year in 2011. CO is seeing influx of seed from Canada, many European varieties and they are worried about influx of PVY-NTN coming in with that. Most states have already been through this and CO seems to be behind the curve, just coming into PVY issues as a major focus and they need to be resolved.

ID: Phil Nolte reported that in 2012, rejected seed lots due to PVY went down to 14% as a result of lower aphid pressure and a good hard frost in the fall. Idaho potato seed certification still seems to be a success story  ELISA testing was a positive change.

MT: Nina Zidack discussed trends of PVY from 2005-2012 across different varieties. 2012 PVY was up similar to other areas, otherwise no major changes across years. No ZC seen.

NE: Steve Marquardt, reported that five percent of lots had PVY in 2011, 6% in 2012. They see Zebra Chip now and then. No major increases or changes in Zebra Chip or other diseases.

WI: Alex Crockford reported that 45% of rejections are due to PVY in normal year and 55% due to variety mix and other issues, like paperwork inaccuracies. More PVY-NTN was seen this year, 10% of PVY positives had NTN. Out of state seed to blame for NTN. No other viruses were of major issue. Psyllid monitoring will start in WI; psyllids are in suction traps in Aug  Sept.

OR: Jordan Eggers, Oregon State U. reported for Jeff McMoran: number of seed lots up 6% from 2011.

WA, Mark Pavek reported that there is an issue with tuber cracking within specialty varieties on West side of WA. Investigation showed a likely correlation between PVY presence and tuber cracking. Commercial seed lot info was handed out indicating PVY incidence and severity has been creeping back up since 2010, but still way below 2004-2008 levels. Leafroll was absent for a second year in the history of the seedlot trial, 2010 being the first  likely due to recent use of neonicitinoid pesticides.

END State Reports

Conference call with Don Thill: Sequestration comments: NIFA letter outlined some reduction in AFRI, currently funded AFRI projects will continue, 2013 there will be fewer new projects; formula funds will be cut for remaining 5.2% from remaining fiscal year 2013  Hatch etc. which will affect research and extension.

Additional Business:

Chris Clark (LSU Ag Center): an update on sweet potato diseases.

Jonathan Whitworth (USDA-ARS, Aberdeen, ID): reported on his upcoming trip to Kenya.

SCRI PVY Reports:

Phil Nolte: Effects of PVY on yield in three varieties. Summary: one percent increase in PVY reduces gross returns by $5.13/A to $18.06 per acre for RB, $5.31 to $15.34 per acre for RN.

Jonathan Whitworth: PVY national screening trials and ELISA vs. visual results in winter testing trials. 16 cultivars from 8 breeding programs submitted. Tuber ring spot on Yukon Gold is used as control  good expression. MSR and MSN clones from Dave Douches program appeared highly resistant to PVY across sites. Results from other clones varied.

Eric Wenninger: Virus-vector interaction studies with different strains and isolates of PVY and different aphid vectors; season colonization of potato by aphid vectors of PVY of Idaho. Green Peach Aphid (GPA) and Potato Aphid (PA) are colonizing species, Bird Cherry Oat Aphid (BCOA) is non-colonizing but because of the high population that moves through potatoes, it can transmit significant proportion of the virus. PVY NTN was transmitted with highest efficiency of the three strains, especially by GPA. Transmission efficiency was greatest by GPA, followed by BCOA and then PA. Seasonal aphid populations appeared near ripening stage of grain (mid to end of July)  potential time to spray grain to prevent movement into potatoes.

Russ Groves: SCRI update, applied research to determine when aphids are flying, when and what to spray and which ones are driving disease cycles. They are discovering developmental patterns such as aphids start to move in the west before they do in the east. There are longitudinal and latitudinal differences and they will need to separate this out for recommendations by location.

Pamela Hutchinson: Effects of hairy nightshade (HNS) density and size on spread of PVY in potatoes. RN was used as the potato host. It only takes one HNS plant per meter row, from potato emergence to harvest, to reduce tuber yield by >20%. HNS serves as host for PVY and vectors. PVY spread is more efficient between HNS plants then between potato plants. Uncontrolled plants will be large by the time aphids start to fly. Larger HNS plants by week three of testing had higher PVY levels than smaller ones. As density of HNS increases, a trend tends to indicate that PVY infection of HNS plants is more likely compared to less dense plants.

Stewart Gray: PVY situation in the US and the reaction of NA cultivars to the various PVY strains. During the 2004-06 survey, PVY-O was the most common. In 2012, we are seeing less O and more PVY NO/NWi and NTN; similar to what happened in Europe in the recent past; which we were able to predict. Shift of strains continues away from PVY-O. Even when aphid picks up PVY-O first, it most likely will transmit PVY-NTN if picked up second. Cultivar differences do exist. Goal is to have major cultivars shown healthy and with symptoms of PVY strains. Strain shift is happening because hybrid recombinants have a fitness advantage, cultivar development has promoted tolerant selections, visual assessment for viruses in cert programs has not worked very well for these, and regulatory policies were not as stringent as necessary.

Alex Karasev: Typing of PVY strains via WA State U Seed Lot Trial. Plants within the WSU seed lot trial with visual mosaic/PVY symptoms were sampled. Eighty nine and eighty five percent of samples visually identified in 2011 and 2012, respectively, tested positive for PVY in lab. Reading error, PVS, PVA, herbicide, and nutritional issues may account for the ones that did not test positive. PVY-O infected 63% and PVY-N:O 27% of positive plants in 2011; during 2012 PVY-O infected 32% with 40% infected with N:O. PVY-NTN and NA-N increased from 2011 by 10% overall. NTN isolates, associated with PTNRD, can be found in seed systems of most states; overall incidence of NTN isolates tends to increase; N-Wi isolates seem to be displacing PVY O in all states. A novel approach of PVY strain differentiation. A new set of primers for better typing of PVY strains is described based on nucleotide polymorphism around main recombinant junctions.

Adjourn until Friday March 15, 2013.

March 15, call to order: 8:10 am

Jordan Eggers: Tubers storage ZC ratings, screen house study and volunteer survey studies. Report of 2011: first foliar symptoms seen in mid-July (via infrared), 1st psyllids observed in August but may have been there earlier, based on difficulty of trapping low numbers. High infection rates due to no insecticide during infectious periods. Question after 2011 was what was going to happen with the volunteer potato plants and are they important in the spread of ZC? Many volunteer plants found. Of the plants collected, only 48.6% of Rangers and 53.3% of Umatilla plants with symptoms actually tested positive. Projection of Lso-infected volunteers was 491 plants/A in Ranger field and 607 plants/A in Umatilla field. Screen house study with Alturas, RN, Ranger, Umatilla, and RB to observe growth and survival patterns after previous year infection. Emergence was greater than expected; most had stunted growth and again, the large terminal leaf. 53% sprouted and produced plants; the control treatment was 99%, 10.3% showed symptoms, 58% of plants with symptoms tested positive for Lso-infection. Symptomatic plants emerged more rapidly than control plants, had fewer sprouts, shorter vines, died earlier (45 days of survival for infected plants, 92 days for healthy plants). Z Chip symptom incidence and severity (in seed) were significant predictors of % emergence. They found that volunteer potatoes can be a source of Z Chip spread. In 2012, ZC incidence was below 1% due to very few volunteers likely due to poor emergence. Herbicides can be used to reduce volunteer number, psyllid populations are not present in large numbers until after volunteers die naturally, psyllids apparently came in high numbers in selected areas in 2011 (didnt seem to happen in 2012), psyllids overwinter in the area but have not been problems in the past (no significant psyllid yellows). They believe that a single TIMELY and effective insecticide application to pivots nearby the hardest hit areas in 2011 effectively and significantly reduced ZC infection. Conclusion: volunteers are not likely to be an important source of ZC, particularly when reasonable control of potato psyllids occurred in the previous and present year.

Jorge Abad: a few years ago they detected a virus from S America in true potato seed. Negative for every test they have in their lab. Deep sequencing indicated a caulimovirus.

Nina Zidack: Comparison of methods for detection of PVY (PCR better detection than ELISA) and PVA (PCR and ELISA similar in results). Observations on varietal incidence of PVA in the field and after artificial inoculation: PVA is a potyvirus, non-persistent aphid transmission, causes yield loss in RB, small yield impact to RN. Prior to 2007 ID and OR started to require PVA is included in total mosaic tolerances for seed lots to be re-certified. MT started in 2007. G1 and G2 seed did not show much PVA compared with G3 seed prior to 2012. They have successfully reduced PVA via testing and rouging. RB appears the most susceptible of the common varieties, Norkotah second; was rarely seen in Classic, DRN, Umatilla, and Ranger. Shepody likely susceptible but they have very few lots in the state. Week 1 after inoculation, real time PCR detected some PVA but ELISA did not. Week 4 both PCR and ELISA were similar. Visual inspections are inadequate for viruses you cannot see, tissue sampling and testing is necessary. Collectively, MT growers may be spending over $12,000 per year to test for PVA.

Jim Crosslin: Potato Moptop Virus (PMTV) susceptibility in cultivars and breeding lines. Sixty two clones planted into 5 hill plots in Grant County, Washington. ELISA worked very well to detect PMTV. Only one clone, POR06V12-3, showed 0 infection within the Non-symptomatic tubers; this clone also had a low percent (3%) of symptomatic tubers. This clone was bred to have PVY resistance, so maybe a link in genetics (?). On the other side of the spectrum, Alpine Russet had 90% infection within symptomatic tubers, RB was at 60%. When symptoms were observed, roughly 70% of the time those symptoms were caused by PMTV. Many clones had high numbers of symptomless tubers that tested positive for PMTV  this is a large concern for processors. Included in this group were RB, Ranger, Umatilla, Alturas, RN, Alpine Russet and many new clones that have not yet been released to the public. Jims first investigation and identification of PMTV in WA was in 2007 after a shipment was stopped at the Mexican border due to PMTV detection. PMTV appears to be more common across the US than once thought (comment by a participant during discussion).

Election of Secretary:

Mark Pavek nominated Carrie Wohleb as Secretary for 2014; approval via vote was unanimous.
Plans for 2014 meeting: Date: Location: similar week in March 2014. Santa Fe, NM or San Diego.

Phil Nolte moved to adjourn at 10:50 am

Adjourn

Accomplishments

PVY: A novel methodology to type PVY strains has been introduced, allowing researchers to distinguish up to nine distinct genotypes of the virus. This technique is based on multiplex RT-PCR technology probing several recombinant junctions in PVY genome.<br /> <br /> PVA: Six years of field testing demonstrated that 100% summer leaf sampling for PVA and roguing of positives in Nuclear and Generation 1 seed potatoes reduced PVA incidence from 15% of PVA infected seedlots in 2007 down to 1.5% of seedlots in the 2012 post harvest test. Summer testing revealed that by far the most susceptible varieties to PVA are Russet Burbank and Russet Norkotah. This observation was backed up by data in greenhouse trials where 10 varieties of potatoes were mechanically inoculated with PVA and leaf samples were analyzed using ELISA and PCR 1 and 4 weeks after inoculation. 4 weeks after inoculation, Russet Burbank and Russet Norkotah showed 70% infection, Dark Red Norland was 30% infected and Classic was 10% infected. Alturas, Amisk, Ranger, Umatilla and Yukon Gold had no detectable virus using Quantitative RT-PCR.<br /> <br /> If PVA becomes a problem in a specific area, certification labs can use summer leaf testing to identify PVA infected plants for roguing, even when the symptoms are too mild to visualize. PVA resistant varieties can be planted as borders around more susceptible varieties to reduce transmission of PVA to early generations.<br /> <br /> Potato mop-top virus (PMTV): Demonstrated that infections with Potato mop-top virus (PMTV) frequently do not produce visible symptoms in infected tubers of many potato cultivars.<br /> <br /> Zebra Chip (ZC): Demonstrated that common potato cultivars grown in the Columbia Basin that are infected with C. Liberibacter solanacearum can produce infected tubers that sprout and grow into infected plants. This can happen in either potato volunteer or potato seed situations. We also showed that these seed borne infections are not likely to be sources of the bacterium for current season spread by potato psyllids due to a number of factors related to when the vector occurs in significant numbers, environmental conditions that normally do not favor the vector, the low number of infected plants that arise from infected tubers, and crop plants that hide infected plants from the vector.<br /> <br /> Despite previous findings, the team discovered that Zebra Chip does display tuber symptoms and can spread through the seed system. Potatoes that overwinter in the soil and emerge as volunteers the next spring can contain Candidatus Liberibacter and may serve as a source for current-season infection of commercial fields.<br /> <br /> It was found that ZC spreading psyllids can and do overwinter in ID, OR, and WA<br /> <br /> Weeds have been found to harbor psyllids which spread ZC; some may be host of Lsoinfection. <br /> <br />

Publications

Alabi, O.J., J.M. Crosslin, N. Saidov, and R.A. Naidu. 2012. First report of Potato virus Y in potato in Tajikistan. Plant Dis. 96:1074.<br /> <br /> Crosslin, J.M. 2013. PVY: an old enemy and a continuing challenge. Am. J. Pot. Res. 90:2-6.<br /> <br /> Karasev, A.V. and Gray, S.M. 2013. Genetic diversity of Potato virus Y complex. American Journal of Potato Research 90: 7-13.<br /> <br /> Galvino-Costa, S.B.F., Figueira, A.R., Rabelo-Filho, F.A.C., Moraes, F. H. R., Nikolaeva, O.V., and Karasev, A.V. 2012. Molecular typing of Potato virus Y isolates from Brazil reveals a diverse set of recombinant strains. Plant Disease 96: 1451-1458.<br /> <br /> Galvino-Costa, S.B., Figueira, A., Camargos, V.V., Geraldino, P.S., Hu, X., Nikolaeva, O.V., Kerlan, C., and Karasev, A.V. 2012. A novel type of Potato virus Y recombinant genome, determined for the genetic strain PVYE. Plant Pathology 61: 388-398.<br /> <br /> Goolsby, J.A., J. Adamczyk, J.M. Crosslin, N. Troxclair, J. Anciso, G. Bester, J. Bradshaw, E. Bynum, L. Carpio, D. Henne, A. Joshi, J.E. Munyaneza, P. Porter, P. Sloderbeck, J. Supak, C. Rush, F.J. Willett, F. Workneh, B. Zechmann, and B. Zens. 2012. Seasonal population dynamics of the potato psyllid (Hemiptera: Triozidae) and its associated pathogen Candidatus Liberibacter solanacearum in potatoes in the southern Great Plains of North America. J. Econ. Entomol. 105:1268-1276.<br /> <br /> McCue KF, Ponciano GP, Rockhold DR, Whitworth JL, Gray SM, Fofanov Y, Belknap WR, 2011. Generation of PVY coat protein siRNAs in transgenic potatoes resistant to PVY. Amer J Potato Res. 89:374-383.<br /> <br /> Nelson, W.R., V. G. Sengoda, A.O. Alfaro-Fernandez, M.I. Font, J.M. Crosslin and J.E. Munyaneza. 2013. A new haplotype of Candidatus Liberibacter solanacearum identified in the Mediterranean region. Eur. J. Plant Path. 135:633-639.<br /> <br /> Nikolaeva, O.V., Roop, D., Galvino-Costa, S.F.B., Figueira, A.R., Gray, S.M., and Karasev, A.V. 2012. Epitope mapping for monoclonal antibodies recognizing tuber necrotic strains of Potato virus Y. American Journal of Potato Research 89: 121-128. <br /> <br /> Quintero-Ferrer, A. and Karasev, A.V. 2013. First report of Potato virus Y in potato in Jalisco, Mexico. Plant Disease 97: 430-430.<br /> <br /> Swisher, K.D., J.E. Munyaneza, and J.M. Crosslin. 2012. High resolution melting analysis of the cytochrome oxidase I gene identifies three haplotypes of the potato psyllid in the United States. Environ. Entomol. 41:1019-1028.<br /> <br /> Whitworth, J.L. and J.M. Crosslin. 2013. Detection of Potato mop top virus (Furovirus) on potato in southeast Idaho. Plant Dis. 97:149.<br />

Impact Statements

1. The new PVY typing methodology is crucial to monitor spread and incidence of new recombinant isolates of PVY. These recombinant isolates of the virus are frequently associated with necrotic reactions in potato tubers.
2. The results obtained suggest that PMTV infections are more common in tubers than would be detected by visual inspection alone. Direct testing of the tubers by serological or molecular methods is necessary for a true picture of the PMTV infection level. This finding has important implications for potato seed certification programs and international trade, necessitating additional tests for PMTV.
3. The data produced demonstrate the need to manage potato volunteers as a possible source of Zebra Chip pathogen. However, it alleviates concerns regarding transmission and transport of ZC in potato seed in the Pacific Northwest.

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Report Information

Participants

1. Karasev, Alex akarasev@uidaho.edu - University of Idaho;
2. Evans, Kelsie kelsiegreen@vandals.uidaho.edu - University of Idaho;
3. Marquardo, Steven smarquardt@nebraskapotatoes.com - PCAN;
4. Jensen, Andy ajensen@potatoes.com - IPC/WSPC/OPC;
5. Cating, Robert Robert.cating@oregonstate.edu – OSU;
6. Abad, Jorge Jorge.A.Abad@aphis.usda.gov - USDA-APHIS;
7. Nolte, Phillip pnolte@uidaho.edu - University of Idaho;
8. Sather, Kent ksather@lamar.colostate.edu – CSU;
9. Leonberger, Kimberly kleonberger@neogen.com - Neogen Corp;
10. Mcmorran, Jeff, jeff.mcmorran@oregonstate.edu - OSU;
11. Houser, Andrew Ahouser@lamar.colostate.edu – CSU;
12. Hamm, Phil Philip.b.hamm@oregeonstate.edu - OSU;
13. Whitworth, Jonathan jonathan.whitworth@ars.usda.gov - USDA-ARS;
14. Thill, Donn dthill@uidaho.edu - UI/AA;
15. Bajet, Narceo B. narceobajet@eurofinsus.com - Eurofins STA Labs;
16. Gray, Stewart smg3@cornell.edu - ARS/Cornell Univ;
17. Siemsen, Susie uplss@montana.edu - MT Seed Cert;
18. Zidack, Nina nzidack@montana.edu - MT Seed Cert;
19. Almeida, Teresa talmeida@colostate.edu - CSU;
20. Rondon, Silvia silvia.rondon@oregontstate.edu - OSU;
21. Wohleb, Carrie cwohleb@wsu.edu - WSU;
22. Jones, Rebecca Rebecca.jones@simplot.com - JR Simplot;
23. Spence, Raina rspence@potatoes.com - WSPC;
24. Guzman, Pablo pguzman@ucdavis.edu - California Crop Imp Assoc;
25. Assis, Francisco fassis@agdia.com - Agdia, Inc;
26. Westra, Alan awestra@idahocrop.com - Idaho Crop Improvement;

Brief Summary of Minutes

Minutes Summary for the WERA-89 meeting
San Diego Downtown Embassy Suites
San Diego, CA, March 20-21, 2014

Chair: Alex Karasev, Univ. of Idaho, Moscow, ID
Vice-chair: Mark Pavek, Washington State Univ., Pullman, WA (absent)
Secretary: Carrie Wohleb, Washington State Univ., Ephrata, WA
Minute taker: Raina Spence, Washington State Potato Comm., Ephrata WA

State Certification Reports:

Colorado – Kent presents. At the post-harvest test, they tested 516 lots in 2013 representing about 7,211 acres. About 3,000 acres were rejected in summer sessions. The rejections were largely due to mosaic. Kent notes their certified seed area is mixed with production areas as well, with Russet Norkotah being a prominent variety. Their tolerance is 1.5% of PVY in the summer, across the generations with some incremental levels for G1 and G2. Kent said the number of rejections in the summer and winter tests have been about equal. PVY NO/Wilga Recombinant (O serotype) and NTN were both found. 12 growers were found to have NTN, in 35 total lots. Kent noted that for export to Mexico (table potatoes), the PVY N testing is very important. With grade defect and generational rejection issues, the growers are very concerned with NTN positives and restrictions on anything positive at post-harvest test for plant back. Colorado has established a zero tolerance on NTN. This went into effect in 2012 with their seed act. Mexico is testing everything incoming.

California – Pablo is expecting 840 acres this year to be submitted for testing. Last year they were a little over 700. Some of this seed is exported to Latin America and the Caribbean. The seed into CA comes mainly from Canada. They also get some seed from ID, OR, MT, NY and NE. They have inspections through November. Last year they rejected 15 acres, because they were above 2 percent disease. In the second inspection, his group saw suspicious symptoms, took 100 to 200 leaves per acre and sent it to the lab in ID. They found that Red Lasoda NY10 at 16% infection. Pablo thinks in this case that the weeds in the ditches of these fields were causing the problem, harboring aphids

Idaho – Alan Westra. Alan presented winter test results. Going in to the winter test, they had 953 lots. 95% of acreage was represented in the winter test. Alan noted that some of the smaller lots are sprout tested. They picked leaves in Hawaii. Leaf roll was not found in the 2013 winter test. The winter PVY test results showed 51.3 lots were totally clean, which represents 37.7 percent of the acreage. 25.4 percent of the lots (40% of the acreage) had PVY at or above 2%. Phil Hamm said as a best practice, growers should know what percent of PVY is in their seed-lots before they buy them. Stewart said they have been advising growers to ask for this information. Jeff noted that some growers have to buy their seed before the results are back, or else there is not enough seed left. Group dialogue about tolerances continued. Alan noted that they have 100% leaf testing by ELISA of everything in the winter test. In 2013, 55% of the lots tested clean.

Montana – Nina Zidack: MT acreage has been steady between 9,500 and 10,500 acres. Nina said this year there was a major hail storm in a seed production areas, defoliating some of the areas in August. At least 2,000 acres were severely hailed in the storm. Some of these fields were left to grow an extra few weeks. MT had uniform emergence in Hawaii grow-outs, and was planted under good conditions. In 2012 they had more virus than 2013. This year they saw later season infection, which may have been due to leaving the plants in the field longer. Nina said most of the Umatilla Russet looked very good this year. Russet Burbank also looked very good this year. The Alturas and Rangers are more problematic, because visually the virus infections are harder to see.

Nebraska – Steve: They had 6,000 acres last year. 4,000 of that was entered into winter test. One lot failed. They had a few lots with herbicide damage. Anything that has virus in plot is put in a not-recommended category. The Nebraska winter grow-out is done in Florida. They test all the latent varieties, and anything new that comes in out of state. The rejected lot this year was a Red Lasoda. Nebraska, New York, Maine, and ND are all still doing winter tests in Florida.

Oregon – Jeff: Their average acreage is around 3,000 in Oregon. PVY varied this year, depending on where they were. Some areas were good, and remained good. Some seed is near commercial acreage, and had high levels after planting mini-tubers based on management challenges. Oregon is a pass through state. Most of their acres are G1 and G2 seed from other states. They have challenges with Norkotah and Rangers. This year some Rangers had no symptoms in summer, and in the winter grow-out they had symptoms. Oregon has winter grow-outs in the greenhouse. Material was sent to Alex for testing. They had PVY NTN, O, and N. They plant at 4 foot by 4 foot grids in the greenhouse. It’s a visual program primarily.

New York – Stewart. Steward will show a slide of the some of the data later in the meeting.

Washington – PVY was a challenge last year, but the seed growers have been working hard to clean up material for this year.

General Research/Extension Discussion:

Stewart Gray, USDA-ARS Cornell, Ithaca, NY: 2013 post-harvest testing with respect to PVY strains and distribution

Stewart presented a slide summarizing the surveillance of the US seed potato crop for PVY recombinants. The percentage of NTN in the overall lots has been variable. N-Wi is becoming much more dominant in the lots. Stewart says no state is free of NTN. Steward reiterated that NTN causes strong strains. Stewart reiterated that PVY management is a business issue and a scientific problem. Stewart encouraged industry to adopt new varieties, and the growers need to ask for information on varieties they are growing. NTN is more fit than other viruses, and in Europe they shifted from PVY O to NTN in about 20 years. We are still a low percentage of NTN infection and it can be controlled. Nina said that in her lab tests, ELISA has adequate functionality to pick up PVY in leaf tissue and is comparable to PCR in that regard.

Nina Zidack, Montana State U, MT: Likelihood of making recertification tolerances given specific PVY levels detected during summer testing

Nina reviewed historical post-harvest data and formulated percentages and summaries. All of Montana’s G1 and G2 summer lots are tested. In G1, they take ten leaves per each family unit. In G2, they take 200 leaves per sample. In G3, they don’t have a requirement that it be tested in summer, but many growers do it voluntarily. Nina clarified that they are composite samples for ELISA. Discussion was entertained about where the analysis formula came from. Phil Nolte says he has the paper that discusses the sampling formula. Alan Westra said Cheri in their lab validated the formula. Conclusions state there are differences between years and generations for PVY levels in G1 and G2. Nina offers this information to growers in her state.

Alex Karasev, U of Idaho, ID: Changes in PVY strains circulating in the Pacific Northwest, 2011-2013

Alex worked with Phil Hamm and Jim Crosslin on this work. The project monitored PVY strains circulating in seed potato in the main potato producing states. Seed lots trails in Othello and Hermiston provide source material for the survey. The typing was done by ELISA and RT-PCR. Alex describes the challenges of seed procurement for Washington State growers, and emphasizes the significance of the seed lot trials. The percentage of PVY O has dropped significantly from 2011 to 2013 in the field trial. Conclusions show that NTN can be found in most states. N-Wi seems to be displacing PVY O. Alex believes breeding for resistance to PVY N-Wi is very important, since PVY O is reducing in prevalence.


Jonathan Whitworth, USDA-ARS, Aberdeen, ID: Progress in developing PVY resistant cultivars in the US potato breeding programs

Jonathan presented data and analysis for breeding lines. Data was shown for aphid versus mechanical transmission from the 2011 Idaho grow-outs. Some of the data shown suggests possible resistance, but the variety may or may not have markers. The data is based upon ELISA tests. Jonathan noted two promising varieties that are showing multi-strain PVY resistance, and one is in the processed trials. Phil Hamm asked if anything has shown powdery scab resistance. Jonathan said not that he is aware of.

Kelsie Evans, U of Idaho, ID: Recombinants of PVY – origins and evolution

Alex introduced Kelsie Evans. Kelsie works in bioinformatics and computational biology as a graduate student in the University of Idaho. She shows a gene graph of common recombinants. Her work involved whole-genome sequencing of a large number of field isolates of PVY from US potatoes. She notes challenges using Genbank when some of the submitted sequences may have been misidentified. She concludes that there are at least 30 unique PVY recombinant structures. Some breaking points are more conserved than others.

Stewart Gray and Alex Karasev: Discussion – Directions for research on PVY and other tuber necrotic viruses

Stewart opened a discussion on the SCRI project on PVY that has been ongoing for the last few years. Both the virus and zebra chip grants are up for renewal. The industry has decided to support both the ZC and virus proposal. So, we can move forward to develop a new virus proposal. Stewart noted they are looking for additional suggestions and participants

Johnathan Whitworth gave a presentation on seed production and work in Kenya. The majority is farmer saved seed that they use. Kenya has many of the same viruses that are present in the U.S. They have bacterial wilt and late blight. Jonathan assisted with developing a lab manual for the local scientist and lab.

Discussion was entertained about challenges with PVS and export shipments.

Nina commented on the issue of tuber core vs sprout vs leaf data that Susie had collected. She presented a graph comparison of the different tissue analyzing data. She wanted to determine if tuber core samples were equivalent to a sprout test. The table showed results for ELISA, PCR and RT-PCR for PVY and PVA. The process of testing the tuber cores, sprouts, and leaves in this manner is labor intensive and will not be taking the place of a grow-out anytime soon. However, Nina notes that this is a good tool and excellent means of detection for growers to plan ahead before the results of postharvest tests.

Alex gave a presentation entitled “An update on PVY strains in Idaho seed supply.” The data presented covered the years of 2009 to 2014. Alex’s lab uses RT-PCR and ELISA in these tests. The testing focuses on the strains known to cause tuber necrosis. All NE-11 samples came from a single producer. NE-11 is associated with tuber damage. Alex noted that tuber symptoms and tuber symptom development in storage is a challenging and complex problem. The 2014 data was from the Hawaii grow-out, and the stand was much better than prior years. PVY O types found are reducing in number. Discussion was entertained about how N-Wi is the dominant strain now in most states.

Carrie Wohleb gave a presentation on her psyllid sampling network in the Columbia Basin. She noted that we have a look-alike problem purple top in potato that is difficult to differentiate from Zebra Chip. Carrie discussed the overwintering of psyllids on the PNW on bittersweet nightshade, which is common in the region. Challenges of identifying tuber and foliar symptoms and testing for the pathogen were discussed.

Phil Hamm gave a brief presentation on zebra chip based upon his observations and work in the Pacific Northwest. Phil discussed the confusion regarding spray programs to control psyllids and their efforts to improve management.

Impact statements for 2014: Alex calls for impact statement submissions

Nina said all of the strain work would be relevant, and quantification of strain compositions important.

Nina’s work comparing winter grow-out data with summer inspection data is important.

Jonathan’s work on the varieties, showing the response of varieties to the different strains of PVY. Progress in developing PVY resistance. Evaluating new potential cultivars.

Document success in virus management such as ZC. This group provides expertise to industry needs.

Work Alex and Kelsie did on strain diversity and genetics – changing population. PVY Wi is the most diverse recombinant that occurs.

Discussion was held about future locations.

Alex moves to adjourn 11:34
Andy seconded the move to adjourn.

Accomplishments

Potato Virus Y (PVY)<br /> <br /> Potato breeding programs are focusing more on developing Potato virus Y (PVY) resistance cultivars. In a nationwide trial, 13 advanced breeding lines/new cultivars were submitted from six U.S. potato breeding programs and screened for PVY resistance. The trials were conducted in Idaho, Wisconsin, and New York. Results showed that 6 lines had high levels of resistance (immunity in 4) to PVY. These 4 lines are resistant to 3 strains of PVY (PVY-O, PVY-NTN, PVY-N:O). One of these PVY immune clones is being used as a parent in Michigan and Maine breeding programs to develop new varieties. A second set of entries from U.S. breeding programs is currently being tested under the same protocol as the first set. <br /> <br /> An analysis of five years of PVY testing data revealed crucial relationships between the amount of virus detected at summer and postharvest testing (PHT). In Montana, historical data show that for generation 1 seed, if summer tests showed 0 PVY during summer testing there was an 87% chance that the seed lot would still be 0 PVY at PHT. Even with 0 PVY in the summer, 6% of the seed lots had >0-0.5% PVY and 7% actually exceeded the plant back standard of 0.5%. In this situation, the PVY inoculum is most likely coming in from potatoes planted around the seed plot. At low but detectable summer levels of PVY (>0-0.1%), there are distinct difference between the generations which are most likely due to the intensity of testing, inspection and roguing in the G1. At this level of summer infection, growers still have a 72% chance of getting G1’s back to 0. For G2 and G3, there is only a 45% and 34% chance of getting 0’s at PHT when you start out at that same >0-0.1 level. This is distinctly different than the situation where you start out with infection levels of >0.1-0.5%. At this higher level of infection, there is a 70% chance that the G1 seed lot will not make a plant back threshold of 0.5% which is equivalent to G2 at 70% and very close to G3 at 67%. <br /> <br /> Based on phylogenetic analysis of 119 newly sequenced whole genomes of PVY and 166 genomes deposited in the GenBank database, substantial heterogeneity was revealed in the PVY-O and PVY-N strains, producing several distinct lineages. Analysis of the recombinant strains of PVY suggested that the PVY-N-Wi strain was the most heterogeneous, and likely arose multiple times from different parental PVY-O and PVY-N genomes.<br /> <br /> Three year typing of PVY isolates collected in the Othello and Hermiston potato seed lot trials indicated a drastic shift in PVY strain composition. Between 2011 to 2013, the proportion of the PVY-O strain circulating in seed potato dropped from 60% to 20%, with the concomitant rise in the recombinant strains from 35% to 80%. <br /> <br /> Deep sequencing technology has enabled the analysis of small RNA profiles of virus-infected plants and could provide insights into virus-host interactions. Potato virus Y (PVY) is an economically important viral pathogen of potato worldwide. While much is known about this virus, little or no information is available regarding host response to PVY infection. In this study, Dr. Hanu Pappu and team investigated the nature and relative levels of virus-derived small interfering RNAs (vsiRNAs) in potato cv. Russet Burbank infected with three biologically distinct and economically important strains of PVY, the ordinary strain (PVY-O), tobacco veinal-necrotic strain (PVY-N) and tuber necrotic strain (PVY-NTN). The analysis showed vsiRNAs of 20-24 nt in PVY-infected plants. Considerable differences were present in the distribution of vsiRNAs as well as total small RNAs. The 21 nt class was the most prevalent in PVY-infected plants irrespective of the virus strain, whereas in healthy potato plants, the 24 nt class was the most dominant. vsiRNAs were derived from every position in the PVY genome, though certain hotspots were identified for each of the PVY strains. Among the three strains used, the population of vsiRNAs of different size classes was relatively different with PVY-NTN accumulating the highest level of vsiRNAs, whereas PVY-N infected plants had the least population of vsiRNAs. Unique vsiRNAs mapping to PVY genome in PVY-infected plants amounted to 3.13, 1.93 and 1.70% for NTN, N and O, respectively. There was a bias in the generation of vsiRNAs from the plus strand of the genome in comparison to the negative strand. The highest number of total vsiRNAs was from the cytoplasmic inclusion protein gene (CI) in PVY-O and PVY-NTN strains, whereas from PVY-N, the NIb gene produced maximum total vsiRNAs. In addition to previously reported conserved microRNAs, 258 non-conserved miRNAs as well as 6 novel miRNAs were identified in PVY-infected potato plants.<br /> <br /> The growers of Washington State were well served in the 2013 growing season by key members of the WERA-89 team. Several prominent growers and industry leaders unwittingly purchased seed with a high percentage of PVY infection, and planted over 200 acres of the infected lot under long-term storage processing contracts. To meet the terms of processing contracts, internal defects or damages exceeding a set threshold will lead to a complete rejection of the harvested field. Accurate and prompt typing of the PVY variants present in the lot was provided by Dr. Alex Karasev at the University of Idaho, and an impartial trial of all regional seed lots was conducted by Dr. Mark Pavek at Washington State University. Both of these gentleman provided information imperative for these two growers to make accurate management decisions. <br /> <br /> Information Distribution:<br /> <br /> The creation and updating of the Potatovirus.com web site has been very useful as a reference. Researchers can send vital information to growers quickly and efficiently regarding virus testing of specific varieties. http://www.potatovirus.com/<br /> <br /> Potato Virus S (PVS):<br /> <br /> Potato virus S (PVS) is becoming increasingly important both in incidence and impact in the US and other parts of the world. Five Potato virus S (PVS) isolates from the USA and three isolates from Chile were characterized by Dr. Hanu Pappu based on biological and molecular properties to delineate these PVS isolates into either Ordinary (PVS-O) or Andean (PVS-A) strains. Five isolates, 41956, Cosimar, Galaxy, ND2492-2R, and Q1 were considered Ordinary strains as they incited local lesions on the inoculated leaves of Chenopodium quinoa, whereas the remaining three (FL206-1D, Q3, and Q5) failed to induce symptoms. Considerable variability on symptom expression and severity was observed among these isolates when tested on additional indicator plants and potato cv. Defender. Additionally, all eight isolates were characterized by determining the nucleotide sequences of the coat protein (CP) gene. Based on the biological and genetic properties, 41956, Cosimar, Galaxy, ND2492-2R, and Q1isolates were identified as PVSO. PVS-FL206-1D and the two Chilean isolates (PVS-Q3 and PVS-Q5) could not be identified based on phenotype alone, however, based on sequence comparisons, PVS-FL206-1D was identified as PVSO, while Q3 and Q5 clustered with known PVSA strains. C. quinoa may not be a reliable indicator for distinguishing PVS strains. Sequences of the CP gene should be used as an additional criterion for delineating PVS strains. A global genetic analysis of known PVS sequences from GenBank was carried out to estimate the nucleotide substitution, population selection, and genetic recombination to assess genetic diversity and evolution of PVS. The higher value of nucleotide diversity (?) of the CP gene compared to that of the 11K gene suggested greater variation in the CP gene. Between PVS-A and PVS-O strains, a higher ? value was found for PVS-A. Statistical tests of the neutrality hypothesis indicated a negative selection pressure on both CP and 11K proteins of PVSO, where a balancing selection pressure was found on PVS-A.<br /> <br /> Potato virus S (PVS) is widely prevalent in various potato-producing regions of the world. Late blight resistant (LBR) cv. Defender and a breeding line LBR4106 (A95056-61) were found to be highly susceptible to PVS infection by Dr. Hanu Pappu and his team. Two PVS isolates, PVS-WaDef and PVS-Id4106, isolated from Defender and LBR4106, respectively, were used to characterize the response of LBR cultivars and breeding material. PVS produced distinct and severe symptoms including severe foliar mosaic, necrotic lesions, leaf wilting, and early death of plants. Both isolates were identified as PVSO strain based on the Chenopodium spp. bioassay and phylogenetic analysis of the amino acid sequences of coat protein. Nicotiana occidentalis-37B was found to be a good indicator plant for identifying severe phenotypes of PVS. The response of selected potato cultivars, germplasm, breeding lines, and the pedigree of Defender were evaluated using these two isolates. PVS-Id4106 incited more severe symptoms than PVS-WaDef on selected cultivars and breeding lines.<br /> <br /> Late blight, caused by Phytophthora infestans, is a destructive disease of potato. Defender is the only cultivar in the U.S. with foliar and tuber resistance to this disease. However, this cultivar exhibits susceptibility to infection by Potato virus S (PVS) and severe symptoms appeared on leaves after infection with PVS. PVS is widespread in potato fields in the U.S. To investigate potential interactions between P. infestans and PVS, Dr. Hanu Pappu and team detached leaves of Defender and Ranger Russet (susceptible to late blight), that were either PVS-infected or non-infected, were inoculated with P. infestans BF-05. The amount of sporulation and the extent of lesion expansion on inoculated leaves were measured to estimate late blight severity. When inoculated with P. infestans only, as expected, Defender exhibited discrete, relatively small, dark purple to black hypersensitive reaction-like spots and on an average had twenty times fewer sporangia compared to Ranger Russet. However, in Defender plants infected with PVS, lesion expansion and sporulation increased significantly compared to PVS-free Defender.<br /> <br /> Information Distribution:<br /> <br /> Researchers, growers, and industry can interact more quickly and efficiently. Improved distribution of information allows growers to act quickly on events that could be the difference between profit and loss.<br /> <br /> Zebra Chip and Virus Detection:<br /> <br /> Candidatus Liberibacter solanacearum (Lso), the organism that causes ZC, can be difficult to detect from potato tubers, plant tissue, and the vector, the potato psyllids (Bactericera cockerelli Sulc) due to PCR inhibitors such as competitor DNA (host genomic DNA) or other inhibitors present in the sample. The OSU Hermiston Plant Pathology Lab has been developing a high-fidelity PCR protocol to increase detection of Lso from tubers, plants and potato psyllids. In initial studies, the high-fidelity PCR protocol improved detection of ZC from tubers, leaves, and psyllids by 30-60% over conventional PCR.<br /> <br /> Viruses that cause necrotic symptoms in potato tubers can be difficult to distinguish based on symptoms and frequently require multiple molecular tests to identify the causal agent. We have developed a reverse transcription high-fidelity multiplex PCR protocol that utilizes previously validated primers to detect six different potato viruses simultaneously: Alfalfa mosaic virus (AMV), Tobacco rattle virus (TRV), Tomato spotted wilt virus (TSWV), Potato mop top virus (PMTV), Potato virus Y (PVY), and Potato leafroll virus (PLRV).<br />

Publications

Brown, C.R., K.G. Haynes, M. Moore, M.J. Pavek, D.C. Hane, S.L. Love, and R.G. Novy. 2013. Stability and Broad-sense Heritability of Mineral Content in Potato: Potassium and Phosphorous 90:516-523.<br /> <br /> Chikh Ali, M., Karasev, A.V., Furutani, N., Taniguchi, M., Kano, Y., Sato, M., Natsuaki, T., and Maoka, T. (2013) Occurrence of Potato virus Y strain PVYNTN in foundation seed potatoes in Japan, and screening for symptoms in Japanese potato cultivars. Plant Pathology 62: 1157-1165.<br /> <br /> Gray, S., Whitworth, J., Xu, H., Singh, R., and Karasev, A. (2013) ST 01: The current state (2012) of Potato virus Y (PVY) affecting potato grown in North America. NAPPO Science and Technology Documents, August 2013. NAPPO: North American Plant Protection Organization.<br /> <br /> Karasev, A.V. and Gray, S.M. (2013) Continuous and emerging challenges of Potato virus Y in potato. Annual Review of Phytopathology 51: 571-586.<br /> Lin, Y-H, J. Abad, C. J. Maroon-Lango, K.L. Perry, and H.R. Pappu. 2014. Molecular characterization of domestic and exotic Potato virus S isolates and a global analysis of genomic sequences. Archives of Virology. In press.<br /> <br /> Lin, Y-H., D. A. Johnson, and H.R. Pappu. 2014. Effect of Potato virus S infection on late blight (Phytophtora infestans) in potato (Solanum tuberosum). Amer. J. of Potato Research. In press.<br /> <br /> Naveed, K., N. Mitter, A. Dhingra, and H.R. Pappu. 2014. Comparative Analysis of virus-specific small RNA profiles of three biologically distinct strains of Potato virus Y (PVY) in PVY-infected potato (Solanum tuberosum) cv. Russet Burbank. Virus Research. In press.<br /> <br /> Novy R.G., J.L. Whitworth, J.C. Stark, B.A. Charlton, S. Yilma, N.R. Knowles, M.J. Pavek, R.R. Spear, T.L. Brandt, N. Olsen, M. Thornton, C.R. Brown, S.R. James, D.C. Hane. 2014. Teton Russet: an early-maturing, dual-purpose potato cultivar having high protein and vitamin C content, low asparagine, and resistances to common scab and Fusarium dry rot. Am J Potato Res. 10.1007/s12230-013-9362-8.<br /> <br /> Novy, R.G., J.L. Whitworth1, J.C. Stark, B.A. Charlton, S. Yilma, N.R. Knowles, M.J. Pavek, T.L. Brandt, N. Olsen, M. Thornton, C.R. Brown, H. Lozoya-Saldana, and M.I. Vales. 2013. Palisade Russet and Teton Russet: two new potato cultivars from the Northwest (Tri-State) Potato Variety Development Program. Abstract–The 96th Annual Meeting of the Potato Association of America. Am J Potato Res 90:143.<br /> <br /> Quintero-Ferrer, A., Robles-Hernandez, L., Gonzalez-Franco A.C., Kerlan, C., and Karasev, A.V. (2014) Molecular and biological characterization of a recombinant isolate of Potato virus Y from Mexico. Archives of Virology, published on-line January 9, 2014 (DOI 10.1007/s00705-013-1968-0).<br /> <br /> Whitworth J.L., R.G. Novy, J.C. Stark, S.L. Love, M.K. Thornton, B.Charlton, S. Yilma, N.R. Knowles, M.J. Pavek and X. Wang 2014. Huckleberry Gold: a high antioxidant purple-skin yellow-flesh specialty market cultivar with potato cyst nematode resistance (H1) and Potato virus X resistance (Nb and Rx1). (Accepted – In-Press)<br /> <br /> Swisher, K.D., Sengoda, V.G., Dixon, J., Munyaneza, J.E., Murphy, A.F., Rondon, S.I., Thompson, B., Karasev, A.V., Wenninger, E.J., Olsen, N., and Crosslin, J.M. (2014) Assessing potato psyllid haplotypes in potato crops in the Pacific Northwestern United States. American Journal of Potato Research, published on-line March 1, 2014 (DOI 10.1007/s12230-014-9378-8).<br /> <br /> Zommick, D.H, L.O. Knowles, M.J. Pavek and N.R. Knowles. 2014. In-Season heat stress compromises postharvest quality and low-temperature sweetening resistance in potato (Solanum tuberosum L.). Planta 10.1007/s00425-014-2048-8.<br />

Impact Statements

1. Developing PVY-resistant potatoes using traditional plant breeding techniques indicates commercial PVY-resistant cultivars will likely be available to growers and consumers in the near future. Reducing the PVY load in the US potato supply will lead to more efficient production, a reduction in grower losses, and potentially, a reduction in pesticide use as PVY spread via insects becomes less of a concern.
2. It was discovered that clean potato seed lots may receive more PVY inoculum from neighboring potato lots than was once thought. Early generation seed should be separated from later generation seed to prevent inoculum spread. Intense inspecting and roguing of early seed generations (G1) works to reduce PVY spread in the following seed generation. However, from this research it was found that summer-rouging with high levels of infection was probably not economically feasible.
3. Understanding how PVY viruses evolve is crucial in reducing their ability to spread, survive, and impact plant growth and grower revenue. Identifying this strain shift is likely to lead to improved screening and management techniques in the near future which should reduce grower losses and improve production efficiency. These findings indicate that the three PVY strains interact differently in the same host genetic background and provided insights into virus-host interactions in an important food crop.
4. Having access to scientists specializing in potato viruses is essential to our grower base. Timely detection of virus by WSU and UI researchers in current-season crops helped avoid crop losses of economic significance and fostered a focused research and outreach collaboration with our seed producing partners for the 2014 season. Test results from PVY research were quickly available to these growers enabling them to adjust practices.
5. Understanding the development and differences of each PVS strain will aid researchers in identifying improved management strategies to reduce the spread and impact on potato production.
6. Among all tested potato genotypes, LBR genotypes were found to be highly susceptible to PVS infection compared to other genotypes suggesting a potential linkage between late blight resistance and PVS susceptibility. These findings underscore the need for potato breeding programs to evaluate LBR material for PVS susceptibility.
7. The increased severity of late blight in PVS-infected Defender suggests that PVS negatively impacts late blight resistance in this cultivar. This study demonstrates that late blight resistance in cultivars to be released should be screened for PVS susceptibility.
8. Our results indicate that high-fidelity PCR is more sensitive than conventional PCR when detecting the Zebra Chip pathogen from host tissue and significantly reduces false negatives obtained by conventional PCR. Since only a conventional PCR thermal cycler is required, no new equipment is required for high-fidelity PCR, making it an easy protocol for plant diagnostic clinics to adopt.
9. Not only does this protocol decrease costs and testing time, (testing for all six of these viruses can now be completed in a few hours instead of a stepwise progression of approximately 2 weeks), it also detects mixed infections which previously required multiple molecular tests.

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Report Information

Participants

Abad, Jorge (Jorge.A.Abad@aphis.usda.gov) - USDA-APHIS;
Casteel, Clare (ccasteel@ucdavis.edu) - University of California-Davis;
Champouret, Nicolas (Nicolas.champouret@simplot.com) - Simplot Plant Sciences;
Charkowski, Amy (acharkowski@wisc.edu) - University of Wisconsin-Madison;
Davidson, Robert (robert.davidson@colostate.edu) - Colorado State University;
French, Allan (allan.french@simplot.com) - Simplot NAFG;
Frost, Ken (Kenneth.frost@oregonstate.edu) - Oregon State University;
Funke, Cassandra (sago9913@vandals.uidaho.edu) - University of Idaho;
Guzman, Pablo (pguzman@ucdavis.edu) - California Crop Improvement Association;
Hall, Darren (darren.hall@ars.usda.gov) - USDA-ARS;
Hess, Greg (greg.hess@colostate.edu) - Colorado State University-PCS;
Holden, Zack (zholden@wsu.edu) - Washington State University;
Houser, Andrew (andrew.houser@colostate.edu) - Colorado Seed Certification;
Jensen, Andy (ajensen@potatoes.com) - Idaho Potato Commission, Oregon Potato Commission, Washington State Potato Commission;
Leonbesges, Kimberly (kleonbesges@neogen.com) - Neogen;
Nolte, Phil (pnolte@uidaho.edu) - University of Idaho;
Pappu, Hanu (hrp@wsu.edu) - Washington State University;
Pavek, Mark (mjpavek@wsu.edu) - Washington State University;
Rondon, Silvia (silvia.rondon@oregonstate.edu) - Oregon State University;
Sather, Kent (kent.sather@colostate.edu) - Colorado Potato Certification Service;
Schuetz, Keith (kschuetz@agdia.com) - Agdia, Inc.;
Siemsen, Susie (uplss@montana.edu) - Montana Seed Certification;
Singh, Mathuresh (msingh@potatoesnb.com) - Potatoes New Brunswick;
Templin, Glen (gtemplin@neogen.com) - Neogen;
Wenninger, Erik (erikw@uidaho.edu) - University of Idaho;
Westra, Alan (awestra@idahocrop.com) - Idaho Crop Improvement Association;
Whitworth, Jonathan (jonathan.whitworth@ars.usda.gov) - USDA-ARS;
Wohleb, Carrie (cwohleb@wsu.edu) - Washington State University;
Zidack, Nina (nzidack@montant.edu) - Montana Seed Certification;

Brief Summary of Minutes

Minutes Summary: WERA-89 Annual Meeting
Wyndham San Diego Bayside
San Diego, CA on March 4-5, 2015

Chair: Mark Pavek; Vice Chair: Carrie Wohleb; Secretary: vacant

The meeting started at 8:00 am March 4, 2015. The minutes of the WERA-89 Annual Meeting of March 20-21, 2014 were unanimously approved.

Administrative Advisor Report: Don Thill said that WERA-89 will need to file paperwork this year to renew for another five years. The current project will expire on September 30. The Chair will need to prepare a termination report for WERA-89 and a new proposal needs to be submitted into NIMSS by January 15, 2016. Thill announced that he is retiring so a new Administrative Advisor will be assigned to WERA-89. A copy of the new proposal should be sent to this person by mid-December. R. Davidson, P. Hamm, M. Pavek, and H. Pappu agreed to work on the draft proposal. All of the members of WERA-89 will need to re-enroll in January, 2016.

State Certification Reports: CA - Pablo Guzman reported that CA had about 1,000 acres in the certification program in 2014, which is an increase of about 200 acres. He noted that a lot of “Banana” seed was infected with PVY, but the mosaic symptoms are difficult to see.

CO - Kent Sather reported that total acreage in the certification program in CO decreased in 2014. A lot of acres were rejected in 2013 mostly due to unacceptable levels of PVY. In 2014, there were 582 seed lots = 7,541 acres (not including “Canela Russet” and experimental varieties). He said 303 lots had mosaic and 56 of them had PVY >8%. Sather also noted that “Banana” has lots of PVY problems, and said that it is being replaced by varieties like “Austrian Crescent” and “LaRatte”. The top five russets in the program are “Norkotah”, “Classic”, “Rio Grande”, “Teton”, and “Centennial”. Some are difficult to rogue. In a PVY survey they found that 36% were N:Wi, 38% O, and 2% NTN. Colorado will be requiring a PHT with a 5% mosaic maximum (and no more than 1% N strain) for both recertified and commercial seed sales, including imported lots. This is a change from the zero tolerance for the NTN strain. Sather says they are focused on reducing the overall inoculum level.

ID - Alan Westra reported that acres in the certification program are down 2% from last year. He said many new varieties are being entered in the program and it is a challenge to get to know how each of these express PVY symptoms. He mentioned that three lots in 2014 had PLRV. These lots came from Canada and a couple of them were withdrawn because they were not able to clean them up with rogueing. He said that 109 of 811 lots had mosaic in the summer readings, which is a slight increase in PVY but not enough to affect the amount of certified seed available. Westra also mentioned bacterial ring rot inspection results from a survey conducted in 2014. They inspected 114 stems from 71 seed lots (agglutination). Two lots tested positive and were confirmed with PCR. They also did trace back tests of sister lots; 4400 tuber cores were tested and all were negative.

MT - Nina Zidack reported that 10,200 acres were in the certification program in 2014. Acreage has been steady. She discussed the winter grow out tests and said that emergence of varieties and lots was mostly good. They have been using Rindite instead of GA to encourage emergence. Results of PVY testing were as follows: 0% = 70 lots, 0.5% = 12 lots, 0-5-1% = 7 lots, 1-2% = 7 lots, and >2% = 4 lots. She noted that “Umatilla” is the easiest to see symptoms and rogue, followed by “Russet Burbank”. “Alturas” can be more difficult depending on the PVY strain. “Ranger” is difficult to see symptoms with N strains. “Norkotah” is very difficult to see symptoms and rogue. Zidack reported that growers that separated nuclear and G1 in 2013 had 96% clean G1 in 2014. But, growers that had nuclear and G1 together in 2013 had 73% clean G1 in 2014. Separation of nuclear and G1 is now a recommendation that they are making to growers. Zidack reported less current season spread in 2014 vs. 2013. She suggested this might be attributed to fewer aphids, mineral oil sprays, and/or earlier vine kill and harvest in 2014 (hail damage extended the season in 2013). They are recommending separation of nuclear and GI seed crops and surrounding them with their cleanest G3. They are also suggesting use of a legume or annual rye border, planting as far from other potatoes as possible, a neonicotinoid insecticide at planting, mineral sprays in-season, insecticides that are feeding inhibitors (ex. Beleaf, Fulfill) applied in-season, or new-generation systemics like Movento in-season, and paying attention to when adjacent crops are harvested.

WA - Mark Pavek discussed the Commercial Seed Lot Trial that has been conducted in WA every year since 1978. In 2014, the lots originated from Canada (9%), Idaho (34%), Montana (37%), North Dakota (1%), Oregon (2%), and Washington (13%). Though not totally representative of what is grown, the varieties entered were “Russet Burbank” (20%), “Ranger” (13%), “Russet Norkotah” (15%), “Umatilla” (13%), “Alturas” (7%), “Clearwater” (6%), and other cultivars (27%). PVY symptoms were found in 30% of the lots, blackleg in < 10% of lots, and no PLRV. Some lots had severe PVY infection. It was suggested that Pavek contact state certification agencies about the most severe lots, since this would be helpful information for them.

WI - Amy Charkowski reported that about 8,500 acres were in the certification program in WI in 2014. Acreage is holding steady. She said that they moved the winter grow out to Hawaii this year (instead of Florida) and it cost less. She said the highest rejection rate they have had for PVY was in 2013, but 2014 had fewer rejections. Herbicide damage was a big issue in 2014. Charkowski noted that the N:Wilga strains have been the most problematic in WI and they have not seen much NTN.

Project Reports: Jonathan Whitworth: New varieties with full or partial resistance to PVY. Whitworth reported on a study to characterize strain specific infection reactions in some potato cultivars including “Premier”, “Ranger Russet “, “Yukon Gold”, and “Mountain Gem Russet”.

Nina Zidack: PVY management in seed. Zidack reviewed the results of a study to integrate rogueing, stylet oils, and induced resistance to minimize PVY transmission in seed fields. They found that an insecticide program alone did not reduce aphid transmission of PVY. Mineral oil provided the most significant reduction in PVY transmission and it was enhanced when paired with an insecticide program. Rogueing decreased virus spread when paired with other control measures. Application of BmJ (a Bacillus myccoides isolate) did not reduce PVY spread alone. Mathuresh Singh said application instructions for mineral oils are vague. Rates should be 1.5 to 2.0 L/A, because higher rates can cause phytotoxicity.

Mathuresh Singh: Current season spread of PVY and PVY transmission and translocation studies. Singh said that they have been tracking current season PVY spread in 12-13 fields per year since 2010. They have noted a decrease in PVY spread and severity over the years. This is attributed to the use of mineral oils and insecticides, and improved timing of applications. They have noted that insecticide applications alone are not effective. He also discussed the results of a study comparing mechanical transmission methods. Seed cutting resulted in no transmission, but plant wounding did. Hammering resulted in 90% transmission. Singh also talked about a greenhouse PVY translocation study. They found that PVY travels upward faster than downward. They established a time line of PVY movement in leaves above and below the infected leaf (middle) and also for movement into the tubers.

Hanu Pappu: Update on PVY, PVS, PMTV and TRV work. Pappu reported on the work that his lab has been doing to understand several important potato viruses. His lab has been comparing small RNA profiles of different PVY strains. They are also comparing various PMTV isolates from the U.S. and have found that all carry three overlapping genes (triple gene block) that are important for suppressing host defense response. They are comparing the U.S. PMTV isolates to European PMTV isolates. They are also studying TRV isolates and are creating a database of TRV genome sequences from different areas. Pappu also said that his lab has been studying a common association of late blight resistance and PVS susceptibility in in potato varieties.

Cassandra Funke (and Alex Karasev): Changes in PVY strains circulating in potato in the PNW, and reactions of potato cultivars to different strains of PVY. Funke said they have documented a decrease in PVY-O incidence in the PNW, but an increase in PVY-N:O. She also discussed some work they have done to learn about reactions of several varieties to PVY strains and sources of resistance. They have been looking at the practical consequences of HR-resistance, which may restrict virus movement and prevent systemic PVY infections under certain conditions.

Silvia Rondon: Brief update of aphid work in Hermiston. Rondon has been studying PVY in volunteers and weeds and has found a mixture of PVY strains. In one study she reports that green peach aphids did not appear to differentiate between healthy vs. PVY infected plants when given choice. She has also been comparing PVY transmission rates from weeds to potato with green peach aphids and potato aphids. She reported that green peach aphid transmission of PVY from lambsquarters to potato was 44%, but from potato to potato was 57.5%. Transmission with potato aphids from lambsquarters to potato was 37.5%.

Additional Research/Extension Reports: Andy Jensen reported that seed potato growers in some areas are in need of more education about aphids and aphid monitoring. Some do not monitor aphids and are not familiar with identification of aphids. These growers make regular insecticide applications but do not check to ensure that those applications were effective.

Erik Wenninger and Shaonpius Mondal have been studying aphid transmission of PVY strains. He noted green peach aphids were the most efficient vectors of PVY in their studies, potato aphids were the least efficient, and bird cherry oat aphids in the middle and much more efficient vectors than previously thought.

Wenninger reported that the aphid species complex has varied from year to year at their study sites in Idaho. Absolute abundance has also varied. Silvia Rondon also reported year to year variations in the predominant aphid species in the Columbia Basin. Some of the more common non-colonizing species were bird cherry oat aphid, mint aphid, rose-grain aphid, mealy plumb aphid, cowpea aphid, and pea aphid.

Amy Charkowski opened a discussion about a proposal to lift the 1912 quarantine on importing tubers from countries other than Canada. Mini tubers imported from other countries go through six-month quarantine. Rob Davidson explained that some Colorado growers are pushing to allow PVY-resistant material from Scotland so it can be planted immediately. Jorge Abad said that temporary release permits are already an option for importing potato plant material. A temporary expedited release usually takes six weeks. Davidson said that the temporary permit process should be explained to John Keeling (U.S. Potato Council). It was suggested that a letter from WERA 89 could help and Charkowski would start the process. Everyone agreed that a lift of the quarantine, even for Scotland which is considered an origin of low-risk, would be bad since there is nothing to verify the earlier origins of the material.

Status Report – SCRI PVY: Amy Charkowski reported that the SCRI-PVY project was approved for funding but they have not heard what the funding amount will be.

Election: Carrie Wohleb will move from Vice Chair to Chair. Andrew Houser was unanimously elected as the Vice Chair. Ken Frost was unanimously elected to serve as the Secretary.

The meeting adjourned at 10:00 am March 5, 2015.

Accomplishments

PVY Strain Diversity and Strain Specific Resistance in Potato Cultivars – Karasev et al.<br /> <br /> Interactions of the main strains of PVY with potato cultivars grown in Idaho, Washington, and Oregon were studied to understand the drastic change in strain composition of PVY isolates circulating in the Pacific Northwest. Special attention was paid to strain-specific resistance genes available in North American potato cultivars. PVY strains have been defined based on genetic reactions in potato indicators expressing hypersensitive reaction (HR) response due to the presence of three different N genes. The genetic background of the majority of North American potato cultivars has so far been poorly characterized for the presence of N genes inducing HR towards different PVY strains. To fill this knowledge gap, the HR response was studied in eight potato cultivars elicited by the five strains of PVY (PVY-N:Wi, PVY-NA-N, PVY-O, PVY-Z and PVY-N) circulating in North America. Potato cultivars tested included Russet Burbank, Russet Norkotah, Shepody, Ranger Russet, Western Russet, Alturas, Rio Grande Russet, and Yukon Gem, and standard indicators Desiree and Maris Bard with the known genetic background. Three additional strains (PVY-N:O, PVY-NE11, and PVY-E) were tested on Yukon Gem. This systematic approach allowed the investigators to identify Nytbr and Nztbr genes present in several North American cultivars. Two more new, putative N genes were postulated to be expressed in the cultivar Yukon Gem, and one additional putative N gene was postulated to be expressed in two cultivars, Yukon Gem and Rio Grande Russet. These N genes may represent valuable sources of resistance against multiple strains of PVY. <br /> <br /> Presence of strain-specific resistance genes in new cultivars, in addition to the decline in acreage of Russet Burbank, may explain the observed shift in PVY strain composition from non-recombinant PVY-O to different recombinant strains that do not elicit HR in the majority of potato cultivars. The two practical conclusions from this research are: 1) presence of strain-specific N genes in commercial cultivars needs to be understood and taken into account to correctly manage PVY threat; 2) breeding for PVY resistance must address the most common PVY strains circulating in the field. <br /> <br /> Developing Potato Cultivars Resistant to PVY – Whitworth et al.<br /> <br /> Efforts to develop PVY resistant potato varieties involved the use of putative PVY resistant and susceptible breeding clones and new varieties for screening trials in Idaho, Wisconsin and New York. Two sets of clones were screened each over a two year period. Clones that were submitted for screening trials came from seven breeding programs across the USA. Each set was planted in three separate strain blocks and one block was inoculated with PVY-O, one with PVY-N:O, and one with PVY-NTN. In addition, no insecticides for aphid control were used in the plots. In the first set there were 15 clones in addition to Russet Burbank and Yukon Gold used as controls. Two of the 15 were known to have markers for the PVY resistance gene, Ryadg. A total of four clones, including the two with the Ryadg gene, were not infected by PVY during the season or in subsequent grow-out tests of daughter tubers. Foliar and tuber symptoms were recorded on all clones in the trials. <br /> <br /> A second set of nine clones for these screening trials had four clones with the presence of Ry genes, with two from Ryadg, one from Rysto, and one from Rychc. Results from the two years (2013 and 2014) are not yet complete, but preliminary results show that six of the nine clones are resistant to PVY. The Ryadg, Rysto, and Rychc genes are reported to provide resistance against all strains of PVY. <br /> In addition to these trials, an example of the multiplying effect of advanced breeding lines with PVY resistance is that in 2013, one of the clones in the first set of trials was used in 12 crosses to develop chip, tablestock, and yellow varieties. These crosses were made with a clone developed by Dave Douches at Michigan State University. These 12 crosses resulted in 2973 individuals, all with the potential to have extreme resistance to PVY. <br /> The molecular markers for genes conferring extreme PVY resistance are now being used by breeding programs in the USA. In the USDA-ARS potato breeding program in Idaho, both the Rysto and the Ryadg markers are routinely used to identify second field year selections with these genes. Both genes have been introgressed into the program, and Rychc is currently being introgressed. A variety to be released this year named Payette Russet has the Rysto marker and in two years of field testing at high virus pressure shows no PVY in grow-out tests of daughter tubers. In the same trial, the Russet Burbank controls averaged 85% PVY. In addition to virus resistance, this variety has been trialed by multiple cooperators and scored high in agronomic, processing, and culinary trials. Another PVY resistant variety, Eva, released in 1999 is a round white chipping potato that also has extreme resistance to PVY. <br /> These releases and the increase in the number of putative PVY resistant clones submitted for these trials between the first and second set of clones shows clear progress in developing PVY resistant varieties that are acceptable to the industry. They also demonstrate an emphasis on PVY resistance in breeding programs. As these and other PVY resistant varieties become accepted and more widely grown, the impact is great for the seed grower as rejections and downgrading of seed will decrease and to the commercial grower as yield reduction and quality defects caused by necrotic strains of PVY will be reduced.<br /> <br /> Best Management Practices to Minimize PVY Spread – Singh et al.<br /> <br /> Potato is the most valuable agricultural crop in New Brunswick, Canada. The province is an important seed producer both for Canada and for export to foreign markets. About 47,000 acres of the limited agriculture land in this small province is used for potato seed production every year. Up to 2011, many potato seed lots were testing with high levels of PVY (5 to 10% or more). Specifically, in 2011, 33% tested >5% PVY, and less than 43% tested at or below 2% PVY. Subsequent efforts of the research community to develop and communicate science-based best management practices and strict certification thresholds set by the government have resulted in drastic improvements over the past several years. In 2014, only 1.1% of tested lots were >5% PVY and over 93% were at or below 2% PVY.<br /> <br /> A project tracking PVY spread in commercial potato fields across the potato growing region of New Brunswick was conducted from 2010 to 2014. In total, 16 commercial growers participated, including 56 separate fields and 13 different potato varieties. PVY inoculum was determined at the beginning of the growing season, and then its spread to marked initially virus-free plants was measured through the season and correlated with initial inoculum, aphid abundance, and management practices used in the field. The results make clear that frequent mineral oil spraying at moderate rates (ca. 2 liters/acre, every 5 to 7 days) beginning early (prior to full crop emergence) and continuing season-long helps to reduce PVY spread to uninfected plants. The effectiveness was substantially increased when several of these oil sprays (at least 5) were combined with contact insecticide sprays, especially when more effective lambda-cyhalothrin or flonicamid type insecticides were used. Control fields that were not sprayed with either oil or insecticide showed an average PVY spread ranging 27% to 31% in the first years of the study, which dropped to 11% by 2014. At the same time, intensively sprayed fields had average PVY spread of 14% in 2010, dropping to only 1.2% in 2014. The near 30-fold reduction in on-farm spread of PVY between unsprayed fields in 2010 to intensively sprayed fields in 2014 is largely due to more frequent and better-timed oil spraying combined with numerous insecticide applications of known-effective chemistries. Also contributing to the decline, however, was a better recognition among growers of the value of planting clean seed. This led to a general trend toward lower inoculum in the field over the years; it went from averaging 2.2% PVY-positive plants in 2010 to only 0.6% in 2014. In 2013 and 2014, controlled and replicated experimental field trials were undertaken to test various treatment combinations of mineral oil and insecticide sprays in many small plots within the same field. In 2013, 13 replicated mineral oil and insecticide treatments were planted, but with low PVY inoculum, thus only a slight amount of spread to new plants occurred. It was difficult to distinguish the different effects of each individual treatment in 2013; despite this, trends in the broad categories of the treatments reflected what was observed on commercial farmers' fields. In a redesigned trial in 2014, higher initial inoculum (2.3%) ensured far more potential for PVY spread (up to 17% in control plots). These data more clearly showed that frequent mineral oil spray and combination of mineral oil and insecticide spray significantly reduces PVY spread (down to 7% to 9%) in these controlled experiments, similar to observations on commercial farms. Other important results from the field trials, however, are that increased rates of mineral oil spray (4 liters/acre rather than 2 liters/acre) do not increase the effectiveness of the spray, and confirm the suspicion that insecticide sprays alone (not in combination with mineral oil) do not significantly reduce PVY spread compared to unsprayed control plots. From both experimental field trials and the long study surveying PVY spread and management practices in commercial potato fields, best management practice recommendations have been developed for reducing on-farm spread of PVY. The practices are effective, economically viable and now widely adopted by the local industry. Planting the lowest possible PVY inoculum in seed is recommended as the most cost-effective deterrent against PVY spread. Furthermore, mineral oil sprays are recommended early (before full crop emergence or large aphid abundances) and frequently (every 5 to 7 days; 12 to 15 sprays per season) until top-kill; oil rates at 2 liters/acre mixed as 2-3% oil in water are sufficient, with several of these sprays (at least 5) tank-mixed with foliar contact insecticides such as lambda-cyhalothrin or flonicamid. Spray programs should increase in intensity during the rapid early growth of the crop or periods of higher aphid activity. <br /> <br /> The large-scale survey of New Brunswick growers' practices and PVY spread in commercial fields has been completed, but the experimental field trial will continue and expand to include investigating effects of different strains. By planting known-positive tubers of three major strains of PVY, consistency of inoculum in the treatment plots can be maximized and the possibility of differential rates of spread of the strains can be investigated.<br /> <br /> Symptom Expression of Major PVY Strains in Different Potato Varieties – Singh et al.<br /> <br /> PVY exists in nature as a complex of several distinct and evolving strains. In many major potato producing regions of the world several novel strains (e.g. PVY-N:O and PVY-NTN) have recently emerged that are quickly displacing the traditional "ordinary" strain PVY-O. These novel strains are concerning, as they typically show more cryptic symptoms, hampering field detection, and distinct phytopathology compared to PVY-O. The responses of eleven commercial potato varieties commonly grown across Canada were characterized to infection with different PVY strains. Plants of each variety grown in the greenhouse were artificially infected with one of the PVY-O, PVY-N:O and PVY-NTN strains. While ten of the varieties were easy to infect with all strains, one variety "Eva" could not be infected by any of the tested strains. In infected varieties, visual symptoms on leaves and effects on tubers varied greatly depending on the infecting strain. Generally, most varieties showed strongest visual symptoms and tuber yield reduction with PVY-O; notably, however, varieties "Bintje" and "Innovator" showed mild symptoms and no significant plant vigor or tuber yield reductions with any PVY strain. There was no clear correspondence between the typically more mild visual symptoms from PVY-N:O or PVY-NTN and effects on tuber yield or quality, though several varieties were identified (e.g. "Atlantic", "Chieftain", "Norland" and "Sangre") that showed no significant tuber effects from these strains. A particular concern about PVY-NTN is its potential to cause tuber necrosis, yet only one variety "Envol" showed these symptoms from the eleven varieties tested thus far.<br /> <br /> The characterization of symptom expression in different variety-strain combinations will continue in 2015, with the addition of more potato varieties as well as the replanting of progeny tubers from the 2014 trials to investigate symptoms in secondary infection.<br /> <br /> Mechanical Transmission of PVY and Within-plant Transduction of PVY – Singh et al.<br /> <br /> In the greenhouse, the potential of mechanical transmission of PVY through seed cutting or plant wounding was studied. There is substantial concern in the local industry that these events during planting, field operations or even violent weather phenomena may transfer PVY to neighboring plants. To investigate seed-cutting, known-infected tubers each carrying the PVY-O, PVY-N:O or PVY-NTN strains were manually cut as though being prepared for planting. Without sterilizing the knife, five more known-negative tubers were immediately cut, then all the seed were planted in marked pots to later test if the resulting plant was infected with PVY. Despite testing all three strains and replicating the experiment twice, in no case did PVY spread to the negative tubers. Mechanical transmission between the foliage of the plants, however, did occur easily in the greenhouse setting. Simply hammering together the leaves of an infected and non-infected plant with a pair of stones was sufficient to transfer the virus in 90% of attempts. Firmly squeezing two stems together, as may happen by stepping on plants or striking them with farm equipment, was 60-70% effective at transferring PVY, and even only jostling plants together by blowing a fan on them for a few days caused up to 40% transmission in some trials. Clearly, mechanical transmission of PVY with realistic treatments is a significant potential. In 2015, the investigators will study the potential for mechanical spread in several growers' fields by testing plants adjacent to known-infected plants. These infected plants will be intentionally planted in high-traffic rows (along tractorways) and compared to infected plants in low-traffic control rows.<br /> <br /> After artificially infecting greenhouse-grown plants, the transduction of the virus through the plant was also studied. From inoculation on a leaf half-way up the stem of a ca. 75 day old plant, the results show faster transduction upward into the youngest growing leaves (59% of plants after 12 days) than toward older leaves lower on the plant (53% of plants after 24 days). Downward transduction into developing tubers may be slightly faster, however, as 63% of plants showed infected tubers after 24 days. Further research into rates of virus transduction and distribution in the plant may produce important advice for management, such as the timing and method of top-kill. All three PVY-O, PVY-N:O or PVY-NTN strains were tested individually for the mechanical transmission and transduction experiments, though there were no clear differences between the strains.<br /> <br /> Aphid Vectors and Alternative Sources of PVY on Potatoes – Rondon et al.<br /> <br /> Several strains of PVY have been problematic in potatoes in the Pacific Northwest causing reduction in quality and yield loss. This disease has increased in severity in recent years and represents one of the most common reasons for rejections of seed lots for certification. Potato Virus Y can be vectored by many aphid species and has several alternative weed hosts; however, alternative weed hosts have not been thoroughly investigated in this region. Therefore, weeds and neighboring crops were surveyed for PVY and aphid vectors in Oregon (Umatilla, Morrow, Baker, Union, Klamath counties) and Washington (Franklin and Benton counties) in 2013 and 2014. Fields were monitored for aphids using green tile traps, buckets, inverted leaf blower, berlese funnel, leaf samples and yellow sticky cards. Weeds such as lambsquarters, tumble mustard, prickly lettuce, redstem filaree and bittersweet nightshade were surveyed for presence of aphids and PVY; neighboring volunteer potatoes, wheat and alfalfa were also sampled. Total number of aphids in the lower Umatilla and Morrow counties were some of the highest seen in the last 30 years. Numbers were relatively high in Klamath Basin and in Union-Baker counties as well. Over 20,000 aphids were collected for species identification. The weed and/or crop species that supported the greatest percent of aphids included: alfalfa, wheat, redstem filaree, prickly lettuce, tumble mustard and bittersweet nightshade. Over 30 species of aphids were identified from traps in potato fields. Potato aphid, cereal aphids (bird cherry-oat aphid, corn leaf aphid, etc.), mint aphids and mealy plum aphids were the most abundant species. PVY was found in 50% of the potato fields surveyed, and approximately 30% of the volunteer potatoes sampled in neighboring fields.<br /> <br /> Transmission Efficiency of PVY Isolates by Three Aphid Species – Wenninger et al.<br /> <br /> PVY is transmitted by aphids in a non-persistent, non-circulative manner. Green peach aphid is the most efficient vector in laboratory studies, but potato aphid and bird cherry-oat aphid can also transmit the virus. Studies were conducted with all three of these aphids to evaluate PVY transmission efficiencies for two isolates of each of three PVY strains (PVY-O, PVY-N:O, and PVY-NTN). Treatment also included a sham inoculation. Infected plantlets (Russet Burbank cv.) were used as the virus source and virus-free plantlets were used as the virus recipients. Recipient plants were tested using quantitative DAS-ELISA to assess virus titer and infection percentage five weeks post-inoculation. Positive recipient plants were also tested using RT-PCR to verify the virus strain present. Transmission efficiency in general was highest with the green peach aphid. Green peach aphid and bird cherry-oat aphid transmitted PVY-NTN with greater efficiency than PVY-O and PVY-N:O. Transmission efficiency for all aphid species did not differ significantly between isolates within strains. There were no correlations between plant titer, infection percentage, and recipient plant titer. Bird cherry-oat aphid transmitted PVY at higher efficiency than previously reported, suggesting that it is more important to PVY spread than was once thought. <br /> <br /> Factors Influencing PVY Transmission – Wenninger et al.<br /> <br /> A study was conducted to compare factors that might influence PVY transmission. Infection rates in aphid-inoculated and mechanically inoculated plants were compared across two potato genotypes (Yukon Gold and A98345-1), three PVY strains (PVY-O, PVY-N:O, and PVY-NTN), and two growth stages (pre- and post-flowering). Infection rate and virus titer was measured using DAS-ELISA. Yukon Gold had a higher PVY infection rate than A98345-1 regardless of PVY strain, especially when inoculated mechanically. Infected Yukon Gold plants had higher virus titer and lower tuber mass compared to A98345-1. Yukon Gold was most susceptible to PVY-O, while A98345-1 was most susceptible to PVY-N:O. Across potato genotypes, plants infected with PVY-O had the highest virus titer while plants infected with PVY-N:O had the lowest virus titer. Both cultivars demonstrated age-based resistance, with higher infection rates when inoculated pre-flowering versus post-flowering. This study demonstrates that many factors influence PVY transmission. These factors should be considered when screening genotypes for resistance. <br /> <br /> Potato Mop Top Virus (PMTV) – Pappu et al.<br /> <br /> Potato mop-top virus (PMTV; family Virgaviridae) was reported recently in the Pacific Northwest USA. To better understand the genetic diversity of the virus, the complete genome of an isolate from Washington State (WA) was characterized. Sequence comparisons of the WA isolate with other known sequences revealed that the RNA Rep-encoded RdRp protein and the RNA CP-encoded coat protein displayed >99% amino acid identity with those of two Nordic (RdRp) and several European and North American isolates (CP) respectively. The RNA TGB-encoded TGB 1 and TGB 3 protein sequences had >99% amino acid identity with the corresponding proteins of the Czech and Danish isolates, whereas the TGB 2 protein is identical to the Colombian isolates. Phylogenetic analysis of the viral genes of the WA isolate reflected the close relationship among the WA and European isolates. RFLP analysis of corresponding DNA of RNA TGB and RNA CP revealed that the WA isolate is considered RNA TGB-II and RNA CP-B types, which are prevalent in Europe and other parts of world. This is the first report of the complete genome characterization of PMTV from the Americas.<br />

Publications

Chikh-Ali, M., Gray, S.M., and Karasev, A.V. (2014) A multiplex RT-PCR assay for the detection and accurate identification of the complex strains and recombinants of Potato virus Y. Abstracts of the Annual Meeting of the Pacific Division of the American Phytopathological Society, July 9-11, 2014; Bozeman, MT. Phytopathology. 104: S3.180.<br /> <br /> Chikh-Ali, M., Gray, S.M., and Karasev, A.V. (2014) A multiplex IC-RT-PCR assay distinguishes fourteen recombinant structures of Potato virus Y. Abstracts of the Annual Meeting of the Potato Association of America, July 27-31, 2014; Spokane, WA. American Journal of Potato Researc.h 92: 180.<br /> <br /> Chikh-Ali, M., Rowley, J.S., Kuhl, J.C., Gray, S.M., and Karasev, A.V. (2014) Evidence of a monogenic nature of the Nz gene conferring resistance against Potato virus Y strain Z (PVYZ) in potato. American Journal of Potato Research. 91: 649-654. <br /> <br /> Dahan, J., Thompson, B., Wenninger, E.J., Olsen, N., and Karasev, A.V. (2014) Monitoring prevalence of Liberibacter solanacearum and haplotypes of its insect vector Bactericera cockerelli in Idaho potato fields. Abstracts of the Annual Meeting of the Pacific Division of the American Phytopathological Society, July 9-11, 2014; Bozeman, MT. Phytopathology. 104: S3.180.<br /> <br /> DeBlasio, S.L., Johnson, R., Mahoney, J., Karasev, A., Gray, S.M., MacCoss, M.J., and Cilia, M. (2015) Insights into the polerovirus-plant interactome revealed by co-immunoprecipitation and mass spectrometry. Molecular Plant-Microbe Interactions. 28: 467-481. <br /> <br /> Fageria, M., X. Nie, A. Gallagher, and M. Singh. (2014) Mechanical Transmission of Potato Virus Y (PVY) Through Seed Cutting and Plant Wounding. American Journal of Potato Research. 92(1):143-147.<br /> <br /> Karasev, A.V. (2014) Potato virus Y: a new problem in potato. Abstracts of the European Association of Potato Research, Pathology Section Meeting, November 17-21, 2013, Jerusalem, Israel. Potato Research. 57: 164-165.<br /> <br /> Karasev, A.V. (2014) Recombinant strains of Potato virus Y – a new problem in potato. Abstracts of the Annual Meeting of the Pacific Division of the American Phytopathological Society, July 9-11, 2014; Bozeman, MT. Phytopathology.104: S3.182.<br /> <br /> Lin, Y.H., J.A. Abad, C.J. Maroon-Lango, K.L. Perry, and H.R. Pappu. (2014) Molecular characterization of domestic and exotic potato virus S isolates and a global analysis of genomic sequences. Achrives of Virology. 159(8):2115-2122.<br /> <br /> Lin, Y.H., D.A. Johnson, and H.R. Pappu. (2014) Effect of Potato Virus S Infection on Late Blight Resistance in Potato. American Journal of Potato Research. 91(6):642-648.<br /> <br /> Murphy, A.F., R. Cating, P.B. Hamm, and S.I. Rondon. 2014. Evaluating sources of aphid vectors and Potato Virus Y in eastern Oregon and Washington. Abstracts of the Annual Meeting of the Potato Association of America, July 27-31, 2014; Spokane, WA. American Journal of Potato Research 92: 64. <br /> <br /> Murphy, A.F., A. Moreno, A. Fereres, and S.I. Rondon. 2014. International endeavors in investigating Potato Virus Y trasnmission. Abstracts of the Annual Meeting of the Potato Association of America, July 27-31, 2014; Spokane, WA. American Journal of Potato Research. 92: 37. <br /> <br /> Naveed, K., N. Mitter, A. Harper, A. Dhingra, and H.R. Pappu. (2014) Comparative analysis of virus-specific small RNA profiles of three biologically distinct strains of Potato virus Y in infected potato (Solanum tuberosum) cv. Russet Burbank. Virus Research. 191(1):153-160.<br /> <br /> Nikolaeva, O.V. and Karasev, A.V. (2014) Antigenic structure of Potato virus Y. Abstracts of the European Association of Potato Research, Pathology Section Meeting, November 17-21, 2013, Jerusalem, Israel. Potato Research. 57: 165.<br /> <br /> Quintero-Ferrer, A., Evans, K.J., and Karasev, A.V. (2014) Genetic diversity of the NE-11 strain of Potato virus Y. Abstracts of the Annual Meeting of the Pacific Division of the American Phytopathological Society, July 9-11, 2014; Bozeman, MT. Phytopathology. 104: S3.183.<br /> <br /> Quintero-Ferrer, A., Robles-Hernandez, L., Gonzalez-Franco A.C., Kerlan, C., and Karasev, A.V. (2014) Molecular and biological characterization of a recombinant isolate of Potato virus Y from Mexico. Archives of Virology. 159: 1781-1785. <br /> <br /> Ramesh, S.V., G. Raikhy, C.R. Brown, J.L. Whitworth, and H.R. Pappu. (2014) Complete genomic characterization of a potato mop-top virus isolate from the United States. Archives of Virology. 159(12):3427-3433.<br /> <br /> Rowley, J.S., Gray, S.M., and Karasev, A.V. (2015) Screening potato cultivars for new sources of resistance to Potato virus Y. American Journal of Potato Research. 92: 38-48.<br /> <br /> Tyler, D., B. MacKenzie, M.S. Fageria, X. Nie, and M. Singh. (2014) Effects of Crop Management Practices on Current Season Spread of Potato Virus Y. Plant Disease. 98(2):213-222.<br /> <br /> Shrestha, D., E.J. Wenninger, P.J. Hutchinson, J.L. Whitworth, S. Mondal, S.D. Eigenbrode, N.A. Bosque-Perez. (2014) Interactions among potato genotypes, virus strains, and inoculation timing and methods in the Potato virus Y and green peach aphid pathosystem. Environmental Entomology. 43:662-671.<br /> <br /> Swisher, K.D., Sengoda, V.G., Dixon, J., Munyaneza, J.E., Murphy, A.F., Rondon, S.I., Thompson, B., Karasev, A.V., Wenninger, E.J., Olsen, N., and Crosslin, J.M. (2014) Assessing potato psyllid haplotypes in potato crops in the Pacific Northwestern United States. American Journal of Potato Research. 91: 485-491.<br /> <br />

Impact Statements

1. We have a better understanding of host responses to the different PVY strains circulating in North American potato cultivars thanks to work that has recently been conducted by team members. This information should be useful to potato breeding programs.
2. There has been significant progress in the development and release of PVY resistant cultivars. This is the result of making PVY resistance breeding a priority. This will have a significant positive impact on the potato industry; as PVY resistant cultivars are more widely grown there will be fewer rejections and less downgrading of seed due to PVY infection, fewer yield losses due to PVY infections, and fewer quality defects caused by necrotic strains of PVY.
3. There has been a significant decline in PVY in seed potatoes produced in New Brunswick, Canada since 2011. This is mostly attributed to the efforts of researchers to develop and communicate science-based best management practices for minimizing the spread of PVY. Best management practices developed and verified in New Brunswick and elsewhere can potentially improve PVY management in other regions where seed potatoes are grown.
4. Our colleagues have demonstrated that bird cherry-oat aphid is capable of transmitting PVY at higher efficiency than previously reported, suggesting that it is more important to PVY spread than was once thought. This information may result in some modifications to current aphid-management strategies that are aimed at control of aphids known to colonize potato fields.

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Report Information

Participants

Bag, Sudeep (sudeep.bag@oregonstate.edu) – Oregon State University;
Blua, Matthew (mblua@potatoes.com) – Washington State Potato Commission;
Chikh-Ali, Mohamad (mohamad.chikhali@simplot.com) – J.R. Simplot Co.;
Davidson, Robert (robert.davidson@colostate.edu) - Colorado State University;
Fulladolsa, Ana Cristina (ana.fulladolsa@wisc.edu) – University of Wisconsin-Madison;
Guzman, Pablo (pguzman@ucdavis.edu) - California Crop Improvement Association;
Hall, Darren (darren.hall@ars.usda.gov) - USDA-ARS;
Jensen, Andy (ajensen@potatoes.com) - Idaho Potato Commission, Oregon Potato Commission, Washington State Potato Commission;
Jones, Rebecca (rebecca.jones@simplot.com) – J.R. Simplot Co.;
Karasev, Alexander (akarasev@uidaho.edu) – University of Idaho
Marquardt, Steven (smarquardt@nebraskapotatoes.com) – Potato Certification Association of Nebraska;
Mizicko, John (johnmizicko@eurofinsus.com) – Eurofins STA Labs;
Pavek, Mark (mjpavek@wsu.edu) - Washington State University;
Siemsen, Susie (uplss@montana.edu) - Montana Seed Certification;
Weber, Erin (elweber2@wisc.edu) – University of Wisconsin-Madison;
Westra, Alan (awestra@idahocrop.com) - Idaho Crop Improvement Association;
Whitworth, Jonathan (jonathan.whitworth@ars.usda.gov) - USDA-ARS;
Wohleb, Carrie (cwohleb@wsu.edu) - Washington State University;
Zidack, Nina (nzidack@montant.edu) - Montana Seed Certification;

Brief Summary of Minutes

Minutes Summary: WERA-89 Annual Meeting

DoubleTree Suites by Hilton Tucson Airport

Tucson, AZ on March 2-3, 2016

Chair: Carrie Wohleb; Vice Chair: Andrew Houser; Secretary: Ken Frost

The meeting started at 8:00 am March 2, 2016. The minutes of the WERA-89 Annual Meeting of March 4-5, 2015 were corrected and then unanimously approved.

Administrative Advisor Report:  Alex Karasev reported for the new WERA-89 Administrative Advisor, Mark McGuire, who was unable to attend.  The WERA-89 group was praised for being very active and submitting documents on time.

State Certification Reports: 

CA - Pablo Guzman noted some issues that came up while inspecting potato seed crops in California in 2015. He said two seed lots with mop top virus were found in an ‘Atlantic’ seed crop.  He noted that the symptoms were very difficult to see pre-bloom.  The symptoms resembled those of frost injury or potato calico (alfalfa mosaic virus), but there was no alfalfa grown in the area.  Guzman shared several images with the group.  The foliar lesions are usually less splotchy than calico symptoms, are often in a “V” shape, and tend to bleach out.  He noted that a nearby commercial potato field with powdery scab and mop top virus is probably the source of the problem in the seed field.  The commercial potato field has been under continuous potato production.  Guzman said the grower uses separate equipment to work the potato seed fields.  California does not reject seed lots for mop top virus per se, but there is the 0.5% tolerance under the Canada/US-Management Plan for Potato Viruses that Cause Tuber Necrosis.  It was noted that many varieties do not show significant necrotic tuber symptoms, including ‘Atlantic’.  There was a discussion about the prevalence of mop top in seed potato crops.  Alan Westra said spraing symptoms are found occasionally in the Idaho seed program, and when tested, usually turn out to be mop top or alfalfa mosaic virus, rather than tobacco rattle virus.  Idaho is getting rid of their zero tolerance for tobacco rattle virus.  He noted finding mop top in seed fields belonging to 4-5 growers in the past few years.  Rob Davidson said that mop top has been found on two farms in three seed lots over the past three years in Colorado.  He noted that tobacco rattle virus used to be more common.    

Guzman talked about a potato seed field with several varieties that had alfalfa mosaic virus.  He saw more symptoms in ‘White Rose’ than in ‘Granola’, ‘Red Lasoda’ or ‘Atlantic’.  There was a discussion about why this might be. 

Guzman was asked to do a late inspection of a seed crop in Arizona destined for Central America.  He noted that it was difficult to inspect the crop because it was senescing.  Later, he heard that zebra chip was found in the shipment and the potatoes were destroyed.  He learned about this by chance from the grower and did not hear anything from USDA-APHIS.  He does not know who did the testing.  The WERA group discussed the spread of zebra chip through infected tubers.  It was noted that transmission from infected seed tubers is rare, but can occur occasionally.  There were concerns by the group that APHIS does not always contact the state agency when potato seed issues arise.  Instead, they notify the U.S. Potato Board and state agencies are left out of the information loop.  Nina Zidack will be serving on the Seed Taskforce Committee and will bring this issue up at their next meeting.  Zidack suggested that all of the state potato seed agencies write case histories to demonstrate times when they found they were kept out of the information loop.    

CO  - Rob Davidson used a PowerPoint presentation provided by Andrew Houser, who could not attend the meeting this year, to present the seed report for Colorado.  He reported that Kent Sather is moving to North Dakota and will work with the seed program there.  Andrew Houser is now the Manager of the Colorado Potato Certification Service.  Greg Hess is now the disease testing Lab Supervisor.  Davidson reviewed the history of rejections for mosaic in Colorado.  He noted that there has been a drop in rejected acres since they adopted the Colorado Seed Potato Act, which lowered tolerance for mosaic viruses to 5% maximum in the post-harvest test.  They are seeing fewer lots with very high infection rates and think the new rules have helped significantly.  They are also seeing a cultivar shift to those with less susceptibility for PVY.  He noted excellent resistance to all PVY strains for ‘Fortress Russet’, ‘Masquerade’, and ‘Midnight Moon’. 

Davidson talked about the winter testing of Colorado seed lots in Hawaii.  He noted that any lots with over 1% mosaic in the second field inspection were ELISA tested in Hawaii, along with plants visually expressing mosaic in the winter grow-out.  Plants were tested individually.  There were 80 lots of 670 in 2015 with mosaic exceeding the 5% maximum tolerance.  Davidson noted that the Colorado Seed Potato Act has a maximum tolerance of no more than 1% PVY-N serotype strains.  There were two seed lots of 670 in 2015 with PVY-N/NTN over 1%.

ID -  Alan Westra reported that no PLRV was seen in the Idaho seed lots in 2015.  There were three lots with PLRV in the previous year sourced out of Canada.  The Canadian grower said he eased up on aphid controls.  Westra noted that PVY continues to be a significant problem.  The number of clean seed lots decreased 2013-2015, but is still an improvement over the years 2007-2009.  Leaf testing for all seed lots in the winter grow-out was implemented in 2008.  There was significant improvement in the number of clean seed lots after that, but more needs to be done.  Most of the planting stock is coming in with some PVY, but current-season spread is a problem, especially outside of the designated seed management areas in Idaho.  Westra suggested that growers need to focus on the fundamentals for managing current-season spread of PVY.     

Westra noted some concerns about the accuracy of leaf testing for PVY during the winter grow-out.  He said the timing of leaf picking is critical to get a good result.  Leaves picked too early, when the plants are less than 10 inches tall, can have low titer.  Leaves picked late can be problematic because plants tend to grow quickly in Hawaii and then it is difficult to differentiate individual plants.  In both cases, this can result in a tendency to underestimate PVY incidence.  Westra has found that the best results occur when they start picking at a plant height of 10-12 inches and then get it done within ten days.  Westra also studied the importance of composite sample sizes when testing PVY in the winter grow-outs.  He found that composite samples of 5-10 leaves for 400 plants can be good for up to 5% incidence, but can overestimate when incidence is higher than that.

Westra also reported on Idaho’s bacterial ring rot sampling program. 

MT -  Nina Zidack reported that Montana has implemented a garden potato seed program to provide Montana certified seed to gardeners.  There are concerns that potato seed used in home gardens can be a source for virus.  Zidack said the need is for small volumes of seed of many different varieties.

Zidack said that Ian MacRae, University of Minnesota, monitored aphids in the winter grow-out fields in Hawaii using suction traps.  There were very low numbers of aphids collected in Dec-Jan, suggesting that the current-season spread was not a big concern.

Zidack reported an increase in the incidence of PVY in Montana seed lots in 2015, which was not surprising given the significant aphid pressure noted during the 2015 growing season.  The winter grow-out results showed that 30% of seed lots had PVY incidence above the 0.5% tolerance.  She said they like to begin leaf picking for PVY testing at about 40 days after planting.  Zidack reported that G1, G2, or G3 seed lots with more than 0.1% PVY during the summer inspection have almost no chance of making the 0.5% tolerance at the winter grow-out.  It is too difficult to rogue anything over 0.1% in the summer. 

NE – Steve Marquardt reported that the Nebraska potato seed program rejected about 1% of the seed lots for PVY after the winter grow-out in Hawaii.  He noted that volunteer potatoes were a problem in Hawaii.  Cultivars with long tuber dormancy, like Canela Russet, can cause big problems for the winter grow-outs. 

WA -  Mark Pavek talked about the Commercial Seed Lot Trial that has been conducted in Washington every year since 1978.  In 2015, there were 310 seed lots entered in the trial and 52 different cultivars.  He noted an increase in the number of European cultivars.  Most of the seed in the trial was grown in Montana and Idaho.  He said approximately 50% of the seed lots had at least one plant with PVY.

 Project Reports: 

Darren Hall:  Use of Molecular Markers in Potato Breeding.  Hall summarized the objectives of the USDA-ARS Potato Breeding and Pathology Research Program in Aberdeen, ID and noted that much of their efforts have focused on resistance to PVY.  He talked about seed increases and some of the challenges with maintaining virus-free seed for trials and supplying that seed to cooperators.  They have increased rogueing and ELISA testing in second generation material, and are now culling out about 20%.  Neogen kits are being used in the summer for rogueing.  Hall talked about PVY resistance genes, hypersensitive response (Ny) and extreme resistance (Ry), and said they are most interested in extreme resistance against all strains.  They have been looking for molecular markers in second generation clones using a high throughput extraction procedure.  They are using S. andigena (Ry-adg) primers: RYSC# and ADG2/Bbv1; S. stoloniferum (Ry-sto) primers: Yes3-3A; and S. chacoense (Ry-chc) primers: Ry186 and Ry364.    

Ana Cristina Fulladolsa:  Progress in fine mapping the PVY resistance gene Rychc in a diploid potato population.  Fulladolsa discussed two different “pre-breeding” programs to identify molecular markers for virus resistance breeding.  The Wisconsin program identified several PVY resistant clones using markers for Rysto (YES3-3B marker) and Ryadg (RYSC3 marker).   They also confirmed that no major negative traits were associated with PVY resistance and those R genes.  Two PVY resistant S. chacoense clones were found in the core collection from the potato germplasm bank, but published markers linked to Rychc were not efficient in populations derived from the clones.  Shelley Jansky crossed the two resistant clones with US-W4 and other breeding clones with good agronomic traits. SNP genotyping of a population segregating for resistance revealed five SNPs with good correlations with resistance and all were on the end of chromosome IX. They developed PCR-based markers in the region close to the SNPs to use for further genotyping and mapping. They genotyped an XD3 (resistant S. chacoense x US-W4) selfed population and found some recombination (< 5 %) between the markers and the resistance gene, suggesting that the gene is further towards the end of the chromosome. They also found few susceptible individuals and think susceptibility may be associated with a lethal factor. They are continuing to cross XD3 with other clones to develop PVY resistant breeding clones with better agronomic traits.

Sudeep Bag: Coordinating the Vector and Disease Diversity of PVY.  Bag talked about projects that were conducted in Oregon to study population dynamics of aphids and their relationship with virus incidence, the role of weeds as alternate hosts for viruses, and the diversity of PVY strains.  Their trapping protocol for aphids included nine fields with four trap stations per field.  Each trap station included a bucket trap, a yellow sticky card, and a tile trap.  More aphids were collected in bucket traps than with other methods.  They sampled potato leaves at each trap station and tested them for PVY using ELISA and RT-PCR.  PVY incidence was positively correlated with aphid abundance.  The PVY positive leaves were tested for strains and they found PVY-NO (56%), PVY-O (10.3%), PVY-NTN (5.8%), and PVY-NO/NTN (1.1%).  They tested 66 weed samples (14 different types) for PVY and found it in only 1.5% of the samples. 

Alexander Karasev: PVY Survey Update.  Karasev reviewed PVY strain analysis of Idaho seed lots produced in 2014 and 2015 during the winter grow-out in Hawaii.  Seed lots from 2014 included 710 PVY positive samples of 754 mosaic samples tested.  These were typed as PVY-O (13%), PVY-NO/Wi (64%), PVY-NTN (16%), PVY-NE-11 (4%), and mixed or unclassified (3%).  They are working on the seed lots from 2015 now.  Of the 929 samples collected in the 2015 seed lots, 94% were PVY positive.  Karasev also reviewed the strain composition of commercial seed lots tested 2011-2015 in Othello, WA.  The seed lots are obtained from commercial producers in Washington.  The seed is sourced from several seed producing areas in the U.S. and Canada.  He noted dramatic changes in PVY strain composition in the field.  Incidence of PVY-O is decreasing, but recombinant strains are spreading including some that induce tuber necrotic ringspot disorder.  Karasev talked about a screen house study to compare seed-borne PVY symptom expression in four cultivars with three strains (O, NTN, and N-Wi).  He noted that ‘Russet Burbank’ has no strain-specific resistance to PVY, but weak non-specific resistance whereas ‘Alturas’, ‘Umatilla’ and ‘Ranger’ all have significant strain specific resistance against PVY-O.  ‘Alturas’, ‘Umatilla’ and ‘Ranger’ have increased susceptibility to PVY-NTN and PVY-N-Wi relative to ‘Burbank’.  Karasev noted that we are changing strain composition without intending to, because many new cultivars carry the Ny gene against PVY-O and some have the Nz gene against PVY-NTN, but almost no cultivars carry N genes selecting against N-Wi, NE-11, or other recombinants.   

Jonathan Whitworth: SCRI Necrotic Virus Grant – PMTV and TRV.  Whitworth discussed work being done by Whitworth, Gudmestad and Brown to study cultivar reactions to Potato Mop Top Virus (PMTV) and Tobacco Rattle Virus (TRV), and to identify markers for PMTV and TRV resistance breeding.  They compared more than 60 varieties and found a range in symptom expression for varieties planted in a plot with high TRV pressure.  Symptom expression ranged from a low of 0% incidence of corky ringspot in ‘AO03123-2’ to a high of over 90% incidence in ‘AO06191-1’.  They did the same with PMTV and found no internal symptoms in ‘A06021-1T’, ‘CO03202-1RU’, and ‘CO97087-2RU’.  ‘Umatilla’, ‘Pomerelle’, ‘Russet Burbank’, and ‘Russet Norkotah’ also had few internal symptoms.  The highest incidence of internal symptoms (25%) was in ‘Payette’ and ‘A03921-2’.  ‘POR06V12-3’ had low incidence of both TRV and PMTV symptoms.  This clone is being used in a cross with ‘A06084-1TE’ to develop a segregating population for marker development.

Carrie Wohleb: Extension Efforts to Help Washington’s Potato Industry Monitor and Manage Important Insect Pests.  Wohleb talked about the insect monitoring network she coordinates in the Columbia Basin of Washington.  She gave an overview of the program, reviewed seasonal insect pest population patterns, and talked about the pest density population maps that were developed to provide a visual indication of pest population distribution.  Wohleb said they are working on using monitoring data and phenology models to develop maps that forecast pest population densities one or two weeks out.

Election:  Andrew Houser will move from Vice Chair to Chair. Ken Frost will move from Secretary to Vice Chair.  Matthew Blua was unanimously elected to serve as the Secretary.

WERA-89 Meeting in 2017:  Most of the people in attendance agree that the second week of March will be the best time to hold the 2017 WERA89 meeting, but we were reluctant to set a date.  It was suggested that the Chair, Andrew Houser, poll the WERA89 group to decide which week in March 2017 will be the best for all WERA89 participants.  The consensus was that San Diego or San Antonio would be the best locations for the meeting.  The 2015-16 Chair, Carrie Wohleb, suggested that Andrew Houser should start the meeting planning process in the late summer or fall of 2016 since there are usually challenges with finding a good venue and signing contracts.  Also, participants need lead time to get approval to attend the meeting and make flight reservations.      

The meeting adjourned at 10:00 am March 3, 2016.

 

Accomplishments

<p><strong>PVY Assessment during Winter Grow-out of Seed Potatoes in Hawaii</strong></p><br /> <p>Personnel from several states who conduct PVY assessments during winter grow-out of seed potatoes in Hawaii shared observations and compared methods.&nbsp; The information they shared will lead to improved results for all programs.&nbsp; It is clear that the timing of leaf picking is critical for getting accurate results for PVY testing.&nbsp; Alan Westra from the Idaho Crop Improvement Program reported that the best results occur when they start collecting leaves at a plant height of 10-12 inches and then get it done within 10 days.&nbsp; He noted that leaves picked too early, when the plants are smaller than 10 inches tall, can have low virus titer.&nbsp; Leaves picked late can be problematic because plants tend to grow quickly in Hawaii and it is difficult to differentiate individual plants when they are large.&nbsp; In both cases, there is a tendency to underestimate PVY incidence.&nbsp; Westra also studied the importance of composite sample sizes when testing PVY in the winter grow-outs.&nbsp; He found that composite samples of 5-10 leaves for 400 plants can be good for up to 5% incidence, but can overestimate when incidence is higher than that.</p><br /> <p>Ian MacRae, University of Minnesota, monitored aphids in the winter grow-out fields in Hawaii using suction traps in 2015-16.&nbsp; There were very low numbers of aphids collected in Dec-Jan, suggesting that the current-season spread of virus was not a big concern.&nbsp;&nbsp;</p><br /> <p>Personnel from several state programs noted concerns about including cultivars with long tuber dormancy, like Canela Russet, in the winter grow-outs.&nbsp; These cultivars are difficult to assess for virus because of poor emergence, and they have also led to some problems as volunteer potatoes in the following year.</p><br /> <p><strong>PVY Strain Diversity in Potato Cultivars and Practical Consequences of Strain-specific Resistance</strong></p><br /> <p>Strain composition studies since 2011 have shown that incidence of PVY-O is decreasing in the U.S., but recombinant strains are spreading including some that induce tuber necrotic ringspot disorder.&nbsp; What is driving this change in strains? Alexander Karasev suggested that we are changing strain composition without intending to, because many new cultivars carry the Ny gene against PVY-O and some have the Nz gene against PVY-NTN, but almost no cultivars carry N genes selecting against N-Wi, NE-11, or other recombinants.&nbsp; Hypersensitivity resistance (HR) to PVY conferred by N genes is strain specific.&nbsp;</p><br /> <p><strong>Developing Molecular Markers to Assist in Breeding Potato Cultivars Resistant to PVY </strong></p><br /> <p>Potato breeding programs in the Pacific Northwest and Midwest have focused a lot of effort on developing new cultivars with resistance to PVY.&nbsp; Since multiple PVY strains are occurring in potato production areas, breeders are&nbsp; most interested in breeding for extreme resistance to PVY using R genes that are non-strain specific. The Ry-adg, Ry-sto, and Ry-chc genes provide durable resistance against all strains of PVY.&nbsp; Molecular markers associated with these genes are being identified and used to identify early selections from crosses with these genes. The breeders at the USDA-ARS Potato Breeding Program in Idaho have been looking for molecular markers in second generation clones using a high throughput extraction procedure.&nbsp; They are using <em>S. andigena </em>(Ry-adg) primers: RYSC# and ADG2/Bbv1; <em>S. stoloniferum</em> (Ry-sto) primers: Yes3-3A; and <em>S. chacoense</em> (Ry-chc) primers: Ry186 and Ry364. The Wisconsin breeding program identified several resistant clones using markers for <em>Rysto</em> (YES3-3B marker) and <em>Ryadg</em> (RYSC3 marker).&nbsp; They also confirmed that no major negative traits were associated with those R genes.&nbsp; Two PVY resistant<em> S. chacoense </em>clones were found in the core collection from the potato germplasm bank, but published markers linked to<em> Rychc</em> were not efficient in populations derived from the clones.&nbsp; Shelley Jansky crossed the resistant clones with US-W4 and other breeding clones with good agronomic traits. SNP genotyping of a population segregating for resistance revealed five SNPs with good correlations with resistance and all were on the end of chromosome IX. They developed PCR-based markers to use for rapid genotyping and mapping. Their results suggest that the <em>Rychc</em> gene is further towards the end of the long arm of chromosome IX and that PVY susceptibility in their population may be linked to a lethal factor. The breeders continue to cross the resistant materials with clones that have good agronomic traits and evaluating them for resistance, fertility, yield, and quality.</p><br /> <p><strong>Screening Clones and Cultivars for Potato Mop Top Virus and Tobacco Rattle Virus Resistance</strong></p><br /> <p>Potato breeding programs are focusing more on developing cultivars resistant to PMTV and TRV.&nbsp; Whitworth discussed work being done by Whitworth, Gudmestad and Brown to study cultivar reactions to PMTV and TRV, and to identify markers for PMTV and TRV resistance breeding.&nbsp; They compared more than 60 clones and cultivars and found a range in symptom expression for varieties planted in a plot with high TRV pressure.&nbsp; Symptom expression ranged from a low of 0% incidence of corky ringspot in &lsquo;AO03123-2&rsquo; to a high of over 90% incidence in &lsquo;AO06191-1&rsquo;.&nbsp; They did the same with PMTV and found no internal tuber symptoms in &lsquo;A06021-1T&rsquo;, &lsquo;CO03202-1RU&rsquo;, and &lsquo;CO97087-2RU&rsquo;.&nbsp; &lsquo;Umatilla&rsquo;, &lsquo;Pomerelle&rsquo;, &lsquo;Russet Burbank&rsquo;, and &lsquo;Russet Norkotah&rsquo; also had few internal symptoms.&nbsp; The highest incidence of internal symptoms (25%) was in &lsquo;Payette&rsquo; and &lsquo;A03921-2&rsquo;.&nbsp; &lsquo;POR06V12-3&rsquo; had low incidence of both TRV and PMTV tuber symptoms.&nbsp; This clone is being used in a cross with &lsquo;A06084-1TE&rsquo; to develop a segregating population for marker development.&nbsp; This is an important step toward developing more cultivars with resistance to potato tuber necrotic diseases.</p><br /> <p><strong>Potato Virus Detection Training</strong></p><br /> <p>WERA 89 participants from the USDA, University of Idaho, Montana State University, Washington State University, and the University of Wisconsin have been developing a potato virus detection training for growers, inspectors, regulators, and anyone interested in learning more about detection of PVY, PMTV and TRV in field applications.&nbsp; The training will take place at the WSU Othello Agricultural Research &amp; Extension Center on June 20, 2016.&nbsp; They will be demonstrating 40 popular cultivars infected with three PVY strains (O, N-Wi, and NTN).&nbsp; They plan to show tuber symptoms of PVY, PMTV and TRV.&nbsp; They will also update attendees on the latest diagnostic assays for viruses and their vectors.</p><br /> <p>&nbsp;</p><br /> <p>&nbsp;</p>

Publications

<p>Benedict, C., McMoran, D., Inglis, D., and Karasev, A.V. (2015) Tuber symptoms associated with recombinant strains of Potato virus Y in specialty potatoes under northwestern Washington growing conditions. American Journal of Potato Research 92: 593-602. Fig. 1 of this paper has been selected for the cover of the October issue of American Journal of Potato Research.</p><br /> <p>Cating, R.A., Funke, C.N., Kaur, N., Hamm, P.B., and K.E. Frost. (2015) A multiplex reverse transcription (RT) high-fidelity PCR protocol for the detection of six viruses that cause potato tuber necrosis. The <em>American Journal of Potato Research</em> 92 :850-864.</p><br /> <p>Chikh-Ali, M., Bosque-Perez, N., **Vander Pol, D., Sembel, D., and Karasev, A.V. (2016) Occurrence and molecular characterization of recombinant Potato virus YNTN (PVYNTN) isolates from Sulawesi, Indonesia. <em>Plant Disease</em> 100: 269-275.</p><br /> <p>Chikh-Ali, M., *Alruwaili, H., **Vander Pol, D., and Karasev, A.V. (2016) Molecular characterization of recombinant strains of Potato virus Y from Saudi Arabia. <em>Plant Disease </em>100: 292-297.</p><br /> <p>DeBlasio, S.L., Johnson, R., Mahoney, J., Karasev, A.V., Gray, S.M., MacCoss, M.J., and Cilia, M. (2015) Insights into the polerovirus-plant interactome revealed by co-immunoprecipitation and mass spectrometry. <em>Molecular Plant-Microbe Interactions</em> 28: 467-481.</p><br /> <p>DeBlasio, S.L., Johnson, R., Sweeney, M.M., Karasev, A.V., Gray, S.M., MacCoss, M.J., and Cilia, M. (2015) The Potato leafroll virus structural proteins manipulate overlapping, yet distinct protein interaction networks during infection. <em>Proteomics </em>15: 2098-2112.</p><br /> <p>Fulladolsa, A.C., F.M. Navarro, R. Kota, K. Severson, J.P. Palta, and A.O. Charkowski. (2015) Application of marker assisted selection for Potato virus Y resistance in the University of Wisconsin Potato Breeding Program. <em>Am. J. Pot. Res. </em>92:444-450.</p><br /> <p>Mondal, S.; E. J. Wenninger; P. J. S. Hutchinson; J. L. Whitworth; D. Shrestha; S. D. Eigenbrode, and N. A. Bosque-Perez. (2016) Comparison of transmission efficiency of various isolates of Potato virus Y among three aphid vectors. <em>Entomologia Experimentalis et Applicata</em> 158: 258-268.</p><br /> <p>Rowley, J.S., Gray, S.M., and Karasev, A.V. (2015) Screening potato cultivars for new sources of resistance to Potato virus Y. <em>American Journal of Potato Research </em>92: 38-48. &ndash; Fig. 8 of this paper has been selected for the cover of the February issue of American Journal of Potato Research.</p><br /> <p>Wohleb, C.H., T.D. Waters, E.M. D&rsquo;Auria, and D.W. Crowder. (2015) WSU Potato Pest Alerts &ndash; Providing Regional Pest Information and IPM-based Recommendations to Aid Management Decisions. Abstracts of the Papers Presented at the 99^th Annual Meeting of the Potato Association of America. <em>Am. J. of Potato Res., </em>93(2)<em>.</em></p><br /> <p>Wohleb, C.H. (2015) Development and impact of a pest alert system for potato growers in the Columbia Basin of Washington. 8^th International IPM Symposium.</p>

Impact Statements

1. Efforts to characterize symptoms of many different potato cultivars infected with different viruses (PVY, PMTV, TRV) and virus strains (PVY-O, PVY-NTN, PVY-N/Wi) have helped personnel with seed certification agencies correctly identify virus-infected plants when they are doing inspections.

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