WERA-89 (Potato Virus Disease Control) 
Accomplishments

Summary of Accomplishments:

1. Facilitating the interstate cooperation to detect, analyze and determine the distribution of PVY strains. 
2. Informing the USDA officials about the status of the PVY strain problem. 
3. Interacting with regulatory officials on the management of tuber necrotic viruses. 
4. Facilitating the proper testing in seed certification agencies to properly assess the PVY strain diversity in the potato seed industry. 
5. Facilitating the assessment of the potato mop top threat. 
6. Assisting seed certification programs in establishing rules regarding tolerance for tobacco rattle virus in seed. 
7. Assessing new testing technology options so that seed certification agencies can properly evaluate technology upgrades. 
8. Establishing resolutions to guide policymakers on recommended research areas to solve virus problems in potato. 
9. Facilitating team efforts to establish beet leafhopper as sole vector of the phytoplasma 
10. Discovery of Leafhopper Transmitted Virescence Agent as the sole incident of the recent outbreak of Potato Purple Top in Washington State. 

Specific accomplishments:

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 Aberdeen, 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, Aberdeen, 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 possibility of managing PVY-PVA mosaic using early vine kill combined with application of crop oil for seed producers. 

Dan Hane of Oregon State University, Hermiston, 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.

Publications

1.	Alvarez, J.M. 2004. Potato insect pests. In J.L. Capinera (ed.), Encyclopedia of Entomology. Klower Academic Press, 1803-1816. 

2.	Alvarez, J.M. 2004. Nightshade plants are an aphid magnet and also harbor potato viruses. Potato Grower, 33: 44-46. 

3.	Alvarez, J.M. and P.J.S. Hutchinson. 2005. Managing hairy nightshade to reduce potato viruses and insect vectors. Outlooks on Pest Management Journal. 16: 249-252.

4.	Alvarez, J.M. and R. Srinivasan. 2005. Evaluation of hairy nightshade as an inoculum source for the aphid-mediated transmission of potato leafroll virus. J. Economic Entomol. 98: 1101-1108. 

5.	Boydston, R.A., H. Mojtahedi, J.M. Crosslin, P.E. Thomas, T. Anderson, E. Riga. 2004. Evidence for the influence of weeds on corky ringspot persistence in alfalfa and Scotch spearmint rotations. Am. J. Pot. Res. 81:215-225.

6.	Crosslin, J.M., P.B. Hamm, K.C. Eastwell, R.E. Thornton, C.R. Brown, D. Corsini, P.J. Shiel, and P.H. Berger. 2002. First report of the necrotic strain of Potato virus Y (PVYN) potyvirus on potatoes in the northwestern United States. Plant Disease 86:1177.

7.	Crosslin, J.M., P.E. Thomas, and R.W. Hammond. 2003. Genetic variability of genomic RNA 2 of four tobacco rattle tobravirus isolates from potato fields in the northwestern United States. Virus Research 96:99-105. 

8.	Mojtahedi, H., R.A. Boydston, P.E. Thomas, J.M. Crosslin, G.S. Santo, E. Riga, and T.L. Anderson. 2003. Weed hosts of Paratrichodorus allius and Tobacco rattle virus in the Pacific Northwest. Am. J. Pot. Res. 80:379-385.

9.	Mojtahedi, H., J.M. Crosslin, P.E. Thomas, G.S. Santo, C.R. Brown, and J.H. Wilson. 2002. Impact of wheat and corn as rotational crops on corky ringspot disease of Russet Norkotah potato. Am. J. Pot. Res. 79:339-344.

10.	Mojtahedi, H, G.S. Santo, P.E. Thomas, J.M. Crosslin, and R.A Boydston. 2002. Eliminating tobacco rattle virus from viruliferous Paratrichodorus allius and establishing a new virus-vector combination. J. Nematology 34:66-69.

11.	Nolte, P., JL Whitworth, MK Thornton and CS McItosh. 2004. Effect of Seedborne Potato virus Y on Performance of Russet Burbank, Russet Norkotah and Shepody Potato. Plant Disease 88:248-252.

12.	Novy, R.G., Alvarez, J.M., Corsini, D.L., Nasruddin, A., Radcliffe, E.B., and Ragsdale, D.W. 2004. Resistance to PVY, PLRV, PVX, green peach aphid, Colorado potato beetle, and wireworm in the progeny of a tri-species somatic hybrid. Am. J. Pot. Res. 81 (1): 77-78. 

13.	Piche, L.M., R. P. Singh, X. Nie, and N. C. Gudmestad. 2004. Diversity Among Potato virus Y Isolates Obtained from Potatoes Grown in the United States. Phytopathology 94:1368-1375.

14.	Srinivasan, R. J.M. Alvarez, S. Eigenbrode, and N. Bosque-Perez. 2006. Influence of hairy nightshade Solanum sarrachoides (Sendtner) and Potato leafroll virus (Luteoviridae: Poleovirus) on the preference of Myzus persicae (Sulzer) (Homoptera: Aphididae). Envirnomental Entomology. In press.

15.	Whitworth, J.L., P. Nolte, C. McIntosh, and R. Davidson. 2006. Effect of Potato virus Y on yield of three potato cultivars grown under different nitrogen levels.  Plant Disease 90:73-76.