Brief Summary of Minutes of Annual Meeting

Brown convened 1:10 pm. Lorenzen noted new AA, Bohach, couldn't attend but extended best wishes. Brown requested approval of last meeting's minutes. Hane had 1 amendment: Whitworth brought up the point about PVY-N management plan. Motion approved as amended; minutes approved. Brown reminded about accomplishments for 2006 renewal and to secure funding for potato virus-related projects. Bewick gave overview of funding opportunities and distributed handouts of CSREES programs. He suggested group start working on renewal project and importance of a good accomplishment report. He described USDA National Plant Diagnostic Network. Surveillance is major part of network/includes training extension agents and growers. The U MD NIMSS website lists all multistate projects. Participants must fill out Appendix E for WCC-89 membership. Thompson: PVY is concern in Norkotah and Shepody. Gemstar Russet appears to be a sponge. Must investigate what isolation distance is effective and what management recommendations reduce incidence. Susceptibility difference between varieties was noticed. ie, Russestt Burbank had more PVA; no PVA was seen in A9014-2. She gave an update on testing for PYV NTN and corky ring spot. McMorran: 1) OR concern about rouging based on foliar symptoms of TRV, since 95% of potatoes show no foliar symptoms. Tuber symptoms are better indication of infection. 2) National standards seem to be based on politics rather than science. Eg. OR allows G5 with 2% PVY infection. However, they were asked if this could be lowered to 1.5% to meet a common national standard. Is there valid scientific reason for requiring pre-commercial to be certified at 1.5% but not 2.0%? 3) According to Schrages UNECE report regarding PMTV, TRV & PNYn. It was decided that testing on tubers with necrotic symptoms was not practical yet. So why is it considered practical in the US? 4) In the case of aster yellows, OR has no tolerance for disease in field, but we do have tolerances in greenhouse. Should we be concerned about this disease in the seed programs? Thompson expressed concern about difficulties training field inspectors on PMTV. Only images are being used as import of PMTV under permit is not allowed. Haslar: There was a drop of 2600 acres in seed production due to drought and PVY. Some growers could not manage PYV. New PVY resistant varieties on horizon. One tentatively named RioGrande Russet. No recombinant PYV found in CO. Some leaf roll noticed. TRV seen in commercial crop but not in seed crop. Marquardt: No TRV and PMTV in ND. Charkowski: PYV was big issue. Incidence was 4% in 2001, lower in 2002, but back to 4% in 2003. Contributory factor may be planting of Russest Norkotah. However, this year had lowest ever seen in winter test. Border crops ie. rye grass and oils seemed to help. Gray: PVY not big issue. Lambert: PVA a problem for first time. PMTV symptoms being studied. So far, not found in the field. Tubers with necrotic spots found in Ontario and PEI. Cutting tubers to find symptoms seems the most reliable approach for diagnosis. Sun: Gave update on testing for PVY-N. In 2000, 100% tested. ELISA showed one + in each of Ranger, Umatilla, A*410, and Liberty. PVY-N not detected last 2 years. 100% of nuclear and G1 tested for PVY and PVX. For G2, 200 leaves per acre were tested. Use of Admire may have led to drop in PVY infection 2002. Guzman: Only 3 are growers in CA; they buy seed from Canada and WA. Singh: PVY continues to be a problem. Those using oils and rouging produce good seed. Some provinces not allow monitoring. As a result incidence is going up. Research updates - PVY Gray: Presented results of a ME and NY survey. Samples from seed lots from other states, seed farms and commercial farms were surveyed. Symptomatic plants were tested. In imported lots 97% had PVY, 68% PVS and 35% PVX. This does not mean high incidences necessarily just some infection in that percentage of lots. ME and NY farms had lower virus incidence than imported lots. Asymptomatic plants were also tested; 46% had PVS 1% PVY and 1%vPVX. Testing of PYV isolates included inoculating tobacco for necrosis and ELISA using PVY-N specific monoclonal antibody. Some samples were positive without necrosis. PVY-N produces systemic infection in Allegheny; PVY-O causes hypersensitive response (does not go systemic). None of the isolates infected Eva which is extremely resistant. One of isolates exhibited PVY-NTN symptoms. Attempts to use micro tubers for developing assays were not successful. Screening of a potato cDNA library showed the presence of sequences related to cherry rasp leaf nepovirus. Keith Perry of Cornell works on this. Whitworth: Breeding and virus indexing. Advanced clones of Bannock Russet are highly resistant to PVY. Results of a 2 year test were shown. Described symptoms of PVY complex in foliage and tubers. Using PVY strains: N, NTN, N:O, and cultivars: Russet Burbank, Ranger Russet, Alturas, Yukon Gold at two temperature, 10 & 20 C. Lower temp resulted in less symptoms. Provided a suggested definition of the PVY complex. The group felt that this is a very useful and worthwhile effort which is likely to increase the understanding of PYV complex and its diagnosis. A subcommittee formed to review above and suggest a set of descriptors for each strain in PVY complex. Brown nominated Whitworth, Hamm, Berger and Crosslin to the sub-committee. Hall: Provided update on markers associated with PVY resistance using S. andrigena. There was a higher manual transmission of PVY-N than PVY-O. Crosslin: Described the results of ELISA on samples from Phil Hamm and some transgenic lines. The MAb from Agdia, MAb4C3, detects all PVY isolates. He made antisera to synthetic peptides to develop strain-specific antisera but the antisera did not work. He gave an update on the use of RT-PCR to identify N/NTN or PVY O. Hamm: Discussed PVY symptoms and summarized the results of the occurrence of PVY-N, N:O in seed lots from various states and provinces. N, NTN and N:O seemed to be present in most states and Canadian provinces. Piche (Gudmestad's lab): Described work characterizing 58 field isolates from ID, MN, ND, NE, NV, OR, TX and WA. ELISA testing of samples using Agdia antisera and RT-PCR using primers from published reports (J Vir Meth 104:40) to identify PYV complex components. Duplex PCR using S6, S7 and A primers (J Vir Meth 113:69) and recombinant point PCR characterized these isolates. 18% of the isolates did not fit the PVY demarcation. Some N:O had atypical symptoms. Among the PVY N-like isolates 6 types were distinguishable based on tobacco host reaction, production of necrosis in tester varieties and sequence data identifying recombination sites in the viral genome. Adjourned. Brown opened the meeting 4/7 at 8:00 AM. He suggested the group prepare a statement of accomplishments for USDA and potato commissions. Lorenzen: Presented sequencing results, started by Berger and Shiel, now carried on by him. Alturas (N:O) was completed and found to be 93% identical with the Hungarian strain (N strain). Confusion exists in literature about the nature of PVY-N/NTN host response. Based on sequence comparisons, isolate 423 provided by P Hamm appears to be a typical European NTN, shared 99.3% homology with the Hungarian NTN and 93.2% homology with the Swiss PVY-N. The "Montana" isolate showed 99.2% identity with the Swiss PYV N (X97895); the "RRA2" isolate was very similar to the NA-NTN/NA-N strains (99.0%, 98.9%) previously described by Singh. He suggested that there may be some evidence of gene conversion. Singh: Described a new recombinant isolate from Canada. Survey done in Manitoba potatoes showed a PVY-N like which upon further characterization turned out to be a recombinant PVY sharing PVY-N pathotype and PVY-O serotype, considered as PVY N:O. He suggested that the spread of PVY N:O in North America was due to the PVY-O like serological reaction of this isolate. Complete genome of this recombinant isolate was sequenced. The 5 was N-like and 3 was O-like. Hence the anomaly in serological reaction. He described a multiplex RT PCR for specific detection of recombinant PYV isolates and showed the primers specific for recombinant junctions, RJ1, RJ2 and RJ3. He later described a new extraction method for RNA from potatoes that is suitable for conducting RT PCR. The key feature of this method is the use of a liquid form of Triton X ATN available from Sigma. Lent: Described the effect of PVA on yield of Russet Norkotah. PVA was found in 1996 in ID and became serious in 1999. It causes mild symptoms. The objective of the study was to determine the effect of various levels of seed borne PVA on yield of Norktoah. Field data from 2000, 2001, and 2002 at Parma, ID and Hermiston, OR were presented. Burbank showed a 0.1 ton reduction with 1% seed borne PVA infection per acre, whereas Norkotah showed no reduction in yield with seedborne PVA infection. Discussion followed. Chuck Brown asked if we should ignore PVA like we did with PVS. Stewart Gray asked if there is any synergism with other viruses and suggested that caution should be exercised. R.P. Singh mentioned that Bud Wright published some data on this in Potato Journal. Berger initiated discussion on deregulating PVY. Group discussed PVY management plan with respect to US, Canada, and Mexico, and the need to establish tolerance levels. Brown and Hamm suggested resistance should be the long term, high priority goal for managing PYV. Berger moved the group recommend above; Colleen seconded; passed unanimously. It was mentioned that there is a need to recognize that releasing new varieties should take into consideration the detrimental effect of potato cultivars as potential symptomless carriers of PYV. This could be a quality factor. A motion was proposed and passed unanimously. Lorenzen: Gave an update on volatiles in case of PLRV and he mentioned that work is in progress on QTLs. Singh said that CO potato beetle prefers PLRV-infected potatoes. Discussion followed and Juan raised the point of what attracts green peach aphids. He described some of his on-going research on the role of night shade and the behavior of winged and wingless aphids and the progression of disease in potatoes. Henderson asked if there is any data on change in volatiles due to insecticidal treatment. Crosslin: He showed results of his research on the role of weeds in TRV epidemiology. Some weeds were tested for TRV and reproduction of stubby root nematode. He gave a list of weeds that are hosts for nematodes but not for the virus. He showed the results of detection of TRV in hairy nightshade plants by RT PCR in berries and seed of systemically infected plants. No seed transmission detected. TRV was confined to roots. Discussion followed on the role of weeds in TRV spread. TRV was seen occasionally in commercial fields, with zero tolerance in CO and ID. Elections Brown invited nominations for the position of Secretary. Hamm nominated Alvarez. Horton seconded. Uunanimous. Venue: Next meeting in Phoenix, date TBD. Crosslin: gave update on potato phytoplasma including phytoplasma taxonomy. He presented PCR results of potato phytoplasma detection and compared single vs nested PCR. Some nested PCR gave false +s and some gave false -s. He designed primers specific to r-proteins which seemed to improve specificity. Hamm mentioned that controlling leafhoppers early may reduce disease. Munyaneza discussed population dynamics of leaf hoppers and remarked that we need to id the vector so that application timing can be refined. Franc suggested grafting of symptomatic potatoes to tomatoes since leafhoppers do not survive on tomato. PMTV Hamm asked the group about the latest situation regarding PMTV. Based on the information on testing of US potatoes by Canada, Nolte mentioned that the ID Dept. of Ag extensively sampled the area identified by the Canadian report. Results are not available. Lambert said that 32 of 2000 samples were positive in ME. Thompson commented that tubers should be tested instead of leaves and asked if samples can be tested in a central location. Singh mentioned a proposal to develop standardized protocols for screening PMTV under controlled conditions. Foliar symptoms are not common for PMTV and hence tuber testing is required. A motion was made that tuber testing should be used for diagnosis of PMTV. Singh pointed out that foliar symptoms referred to as stem mottle were described in Europe. A Dutch Plant Pathology textbook being translated to English has chapter on stem mottle. Brown asked if there is any transgenic work in potatoes. Appears there is none. PVY management plan Whitworth updated on the status of the plan. He motioned that the group ask NPC Subcommittee on Certification that the document be distributed for final comments with a reasonable amount of comment period allowed prior to final signatures. Seconded by Thompson/unanimously passed. Adjourned 3:00 pm. The following passed unanimously: 1. Critical need to establish criteria for describing the PYV complex. Sub-committee formed. Brown nominated Whitworth, Hamm, Berger and Crosslin. 2. Berger moved highest priority be given to develop potato cultivars immune to PVY complex (non-strain specific). Additionally, the group recognizes there should be an official recognition of the fact that releasing new varieties latent or asymptomatic carriers of viruses is detrimental to the industry in that the necrotic symptom of the tubers is a quality factor. Thompson seconded. 3. Hamm moved that we remove foliar symptoms of tobacco rattle virus (TRV) in management plant because foliar symptoms are not reliable in TRV diagnosis. Davidson seconded. 4. Thompson moved we would not recommend identification of potato mop top virus based on foliar testing until such time it is proven to be reliable. Diagnosis should continue to be based on ELISA testing of tubers. Seconded by Davidson. 5. Whitworth proposed WCC-89 ask the NPC Sub Committee on Certification that the document be distributed for final comments with a reasonable amount of comment period allowed prior to final signatures. Thompson seconded. 6. Brown moved that WCC-89 recognize leadership of outgoing AA, R Heimsch. Hamm seconded.

Ongoing efforts in New York by Dr. Steward Gray from Ithaca, NY and his collaborators include a survey done in ME and NY. Samples from imported seed lots from other states, seed farms and commercial farms were surveyed and symptomatic plants were collected and tested. In imported lots 97% had PVY, 68% PVS and 35% PVX at some level of infection i.e., at least one infected sample. This does not mean high incidences necessarily just some infection in that percentage of lots. ME and NY farms had lower virus incidence than imported lots. Asymptomatic plants were also tested. Results showed 46 % had PVS 1% PVY and 1%vPVX. Testing showed that variety, Eva was highly resistant. Screening of a potato cDNA library showed the presence of sequences related to cherry rasp leaf nepovirus. As part of a continuing effort, Dr. Jonathan Whitworth of USDA-ARS from Kimberly, ID developed advanced clones of Bannock Russet that are highly resistant to PVY. He compiled the symptomatology of the PVY complex in foliage and tubers, using PVY strains: N, NTN, N:O, and cultivars Russet Burbank, Ranger Russet, Alturas, Yukon Gold at two temperature, 10 and 20 C. Provided a suggested definition of the PVY complex. The group felt that this is a very useful and worthwhile effort which is likely to increase the understanding of the PYV complex and its diagnosis. A subcommittee is formed to review the above and to suggest a set of descriptors for each strain in the PVY complex. Darren Hall and Jonathan Whitworth of USDA-ARS, Kimberly, ID are exploring markers associated with PVY Resistance, using Solanum andrigena. Jim Crosslin of USDA-ARS, Prosser, WA has standardized a RT-PCR assay to identify N/NTN or PVY-O. Testing of seed lots by Phil Hamm of Oregon State University, Hermiston, OR showed the occurrence of PVY-N, N:O, and NTN in various states and Canadian provinces which highlighted the need for continued monitoring of seed for these viruses. Neil Gudmestad, North Dakota State University, ND, used various sets of primers to identify the various components of PYV complex in ND. Novel PCR-based approaches such as duplex PCR and recombinant point PCR are being used to characterize various PYV isolates at molecular level. Based on this work, new isolates are found that did not fit the PVY demarcation. Several PYV isolates were sequenced in the laboratory of Jim Lorenzen of University of Idaho, Moscow, ID, which will be useful in determining the sequence identity of several PVY variants. Specific accomplishments include, near completion of whole-genome sequencing of 10 PVY isolates, and PCR assays designed for three newly discovered PVYN:O recombinant junctions. Plans for coming year include, sequencing another 6 to 10 PVY genomes selected by collaborators for novel genotype/phenotype combinations, development of multiplex PCR assay to more accurately differentiate known PVY strain types/recombinants in N. America, development of an infectious PVY clone system to use in hypothesis testing, determination of the effect of PVY, PLRV and PLRV constructs on gene expression of potato leaves using cDNA microarrays (while collaborators determine effect on foliar metabolite content and volatile emission). As part of an ongoing effort to understand the PYV complex, RP Singh of Agriculture and Agri-Food Canada, New Brunswick, found a new recombinant isolate in Canada. Survey done in Manitoba potatoes showed a PVY-N like which upon further characterization turned out to be a recombinant PVY sharing PVY-N pathotype and PVY-O serotype, considered as PVY N:O. He suggested that the spread of PVY N:O in North America was due to the PVY-O like serological reaction of this isolate. Complete genome of this recombinant isolate was sequenced. The 5? was N-like and 3? was O-like which may be the reason for the observed anomaly in serological reaction. A multiplex RT PCR assay for specific detection of recombinant PYV isolates was developed and primers specific for recombinant junctions, RJ1, RJ2 and RJ3 are developed. A new extraction method for RNA from potatoes that is suitable for conducting RT PCR was developed. Based on field evaluations over a three-year period (2000-2002), the effect of PVA on yield of selected varieties, carried out by Melinda Lent of University of Idaho, showed that Burbank showed a 0.1 ton reduction with 1% seed borne PVA infection per acre, whereas Norkotah showed no reduction in yield with seed borne PVA infection. Phil Nolte, Alvarez, Whitworth and Thompson of University of Idaho and USDA-ARS are currently investigating the possiblity of managing PVY-PVA mosaic using early vine kill combined with application of crop oil for seed producers. Dan Hane of Oregon State University, Hermitson, OR is participating in the second year of a national PVY variety susceptibility evaluation for entries received from breeders across the U.S. The project entitled, Characterization of symptom expression to PVY of potato breeding lines advanced from breeding programs in the US and the identification of resistance earlier in breeding, is led by Chritian Thill. Selections from Colorado, Maine, Minnesota, New York, Texas Wisconsin, and the USDA/ARS have been evaluated. Sixty eight entries were evaluated in 2003 of which 4 clones were designated as asymptomatic and 2 with unreadable symptoms in two of four replications in the Hawaiian winter grow-out. Part of the effort is also directed at the environmental component for symptom expression. This season, 105 clones are being evaluated. This effort is directed at identifying asymptomatic clones being advanced in breeding programs as well as comparing the environmental differences between Minnesota and Oregon. Additionally, Phil Hamm & Dan Hane evaluated 8 cultivars this past season for their ability to acquire PVY in a natural field setting. Four of the clones are noted for their spongeeffect when it comes to acquiring PVY Shepody, Russet Norkotah, Gem Russet, and GemStar. The other 4 are not generally as problematic Russet Burbank, Ranger Russet, Umatilla Russet, and Alturas. The purpose is to try to understand whether varieties do in fact become infected with PVY at different rates under field conditions and if so, try to define contributing factors to the differences. This would be of particular use in seed growing areas for managing PVY in seed fields.

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