Brief Summary of Minutes of Annual Meeting

WERA089 minutes - March 12-13 2008. San Antonio, TX Chair Jim Crosslin opened the meeting by welcoming all attendees. Introductions were made. Administrative Advisor Greg Bohach made a few comments about the FY09 budget, we now know there will be no FY09 budget signed by the President and we will be on a Continuing Resolution until the next administration goes to D.C. The new Farm Bill and its provision for big new money for Specialty Crops (which includes potatoes) was discussed. Greg also mentioned a new program was established by State Exp. Station Directors; an Excellence Award for Multistate Projects. Greg and Jim Crosslin did submit a nomination packet for this award. All participants should formally register in NIMSS. State Seed Certification Reports Followed: Pablo Guzman described a new on-line application system that growers use to register fields for inspection and certification. The program is on the California Crop Improvement website and will be available for purchase at some point in the future. If interested contact the Director of CA Crop Improvement. Pablo provided a demonstration of the program which is password protected (Pablo would not share his password so we could not play with the system). Growers supply information on the crop, including variety, generation, seed origin, winter test results, other testing data if available, field information (location, history, date planted). The grower also provides a copy of the Certification Tag. Inspectors carry a laptop with wireless capability to the field and can upload data on site. A most interesting benefit, beyond ease of record keeping, was to provide spatial and temporal information on all fields so that maps can be easily generated showing the geographic distribution of disease and pest problems, crop locations, etc. Jeff McMorran (OR) had a normal season overall in 2007. PVY symptoms were more mild, especially noticeable in Ranger. Some anecdotal evidence that milder symptoms were attributable to the recombinant stain of PVY (PVYN:O or PVYN-Wi as the European's like to call it). Mild symptoms were also noticed in the greenhouse winter trials. Commented that symptoms were more variable in the field than greenhouse. Rob Davidson commented that over the past decade symptoms overall are more mild in the field. There was no major rebuttal to this comment. Andy Jensen did not provide a WA state report, but did offer the comment that commercial growers were applying for exemptions from seed certification law that currently requires all seed entering the state be certified. Seed from within the state can be exempted from certification requirements. Greg Boze reported that the Idaho growers had voted to assay all winter test material using ELISA. The growout was done in Southern CA (Central Valley). There was a slight decrease in incidence and rejected lots in 2007 compared to 2006, but he also commented that 2006 was an odd year. The winter test was not set up to allow a comparison of ELISA and visual symptom comparisons. Anecdotally, there was an increase in mild symptoms observed in the field, and much of this was not related to symptoms within the typical latent varieties-similar to the comment by Jeff McMorran. There were no hard numbers on the cost of ELISA testing vs traditional visual assessment of the winter test. Increase costs included sampling, shipping samples to the lab and lab testing. Greg still felt this was cheaper than doing the winter test in a greenhouse. Using 5 leaves per sample for a 400 tuber sample per lot as a standard he tossed out the cost estimates of ~$260 for greenhouse testing of the material vs ~$75 for field testing. PLRV incidence was on the rise and R. Norkota was the cultivar of choice for rejected lots. A brief discussion ensued regarding the origins of the 400 tuber/lot sample. Phil Nolte indicated that Mike Sun et al. published a paper about this in the Am Pot Journal. SAMPLE-SIZE DETERMINATION FOR SEED POTATO CERTIFICATION Author(s): LUND RE, SUN MKC, AMERICAN POTATO JOURNAL 62: 347-353 1985. Tom Unruh indicated the number of samples is less important than how the samples are collected. Rob Davidson indicated that Colorado had a typical year. 6K acres of R. Norkota did not pass inspection; 50% of these acres were decertified on the basis of the summer inspections and another 30-40% in the PHT. R. Norkota acreage is down in CO this year, and CO farmers are growing another 150 varieties that have few virus problems. Growers are beginning to admit to seeing yield loss due to virus. Gerhard Bestes commented that some Atlantic lots out of CO had some PVY issues this year. Rob also mentioned that CO is working on a Seed Law that will require all potatoes moving into the state be winter tested and certified. Also in-state material will need to meet standards in order to be replanted. Currently any in-state lot can be replanted. Steve Marquardt reported that NE had no rejections last summer and only a handful in the PHT, less than last year. PVY was in R. Norkota. The winter test sample rate in NE is 500 tubers/40 acres. A NE seed law was passed early in March; imported seed must be tested and certified to meet NE tolerance limits (0.5%). NE also tried to conduct winter tests in Puerto Rico this year, the inspections were decidedly more festive than in southern Florida. A series of research updates were provided by the following: Joe Munyaneza, Luis Salazar, Jim Crosslin, Ian Barker, Mathieu Rolland, Babu Srinivansan, Felix Cervantes, Jonathan Whitworth, Alex Karasev, Stewart Gray, Phil Nolte, and Julie Pasche. There was a discussion on revisions to the Necrotic Virus Management Plan based on the information that Stewart Gray had sent out to participants prior to the meeting. There was strong support for the management of PVY strains rather than just managing PVY. This was based on the information from the 3 yr survey that strains are not distributed uniformly around the US and some states would like to keep the necrotic strains out if possible. Since no single test will identify all PVY strain or variant groups each state will have to identify what test they want to be conducted to determine strain/variant identification. Growers will be given the option of asking for more detailed information than just PVY levels, but they will have to have information on the various attributes and shortcomings of the various tests they may request. Perhaps some of this information can be provided in the Management Plan appendices. Discussions on tolerance limits and mandatory PHT did not identify consensus proposals although most agreed that PHT were necessary for recertification and for lots shipped out of state. Also tolerance limits should be defined and are defined for seed shipped between states. The issues are how the PVY incidence is determined and what the appropriate levels are for seed and ware potatoes. The NPC has developed a group of people that represents all aspects of the industry, seed certification and scientific advisors to develop and agree upon a strawman proposal that can be presented to the entire US industry. Once the US industry has agreed upon revisions to the plan then discussions will begin with Canada. Jeff McMorran was elected Secretary The rest of the meeting was devoted to identifying key impacts for NIMSS reporting. Next meeting - Back in San Antonio? Send suggestions to Steve Marquardt Meeting adjourned.

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

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