Biological and Serological Properties of Potato virus Y Isolates in Northeastern United States Potato

A survey of six potato viruses, Potato virus A (PVA), Potato virus M (PVM), Potato virus S(PVS), Potato virus X (PVX), Potato virus Y (PVY), and Potato leafroll virus (PLRV), was conducted in New York and Maine during 2002 and 2003. Leaf samples were tested by enzyme-linked immunosorbent assay and PVY-positive samples were further tested to determine whether a necrotic strain of PVY (PVY^N) or a strain able to induce necrosis in tobacco and in potato tubers (PVY^NTN) were present. In both years, PVY and PVS were identified in a majority of the samples, and mixed infections predominated in 83% of the symptomatic leaves in 2002. Of the total 394 PVY-positive samples, 3 reacted with monoclonal antibody (MAb) 1F5 and caused veinal necrosis (VN) in tobacco. Two of these isolates caused tuber necrosis in the potato cv. Yukon Gold. Three PVY isolates reacted with MAb 1F5 but did not cause VN in tobacco, and two caused VN but did not react with MAb 1F5. None of these eight isolates were able to overcome the Ry resistance gene in the potato cultivar Eva, but several were able to overcome the Ny resistance gene found in Allegany. PVY^N isolates were not widespread in the northeastern United States; however, several PVY isolates differed from both PVY^N and the ordinary strain of PVY and may represent strain recombinants.