Possible Escape of a Recombinant Isolate of Potato virus Y by Serological Indexing and Methods of its Detection.

Surveys of commercial and seed potato fields for virus diseases (1998 to 2002) in Manitoba established that Potato virus Y (PVY) is of concern in seed potato production. To determine the prevalence of PVY strains, PVY-infected tubers identified by reverse transcription-polymerase chain reaction (RT-PCR) from surveys (2000 to 2001) were grown for symptom expression and strain characterization by strain-specific RT-PCR, bioassays, and serological assays. Of the samples collected (2000 to 2001) and tested by RT-PCR, 4.0% contained PVY. Further analysis of the PVY-positive samples by a duplex RT-PCR facilitating the simultaneous detection of common (PVY) and tobacco veinal necrosis strains (PVY) indicated that 37.5% contained PVY and 63.5% contained PVY-type isolates. Analysis of the PVY-type samples using three monoclonal antibodies (MAbs) showed that all reacted with only the PVY MAbs and not with the PVY-specific MAb. Partial nucleotide sequences of both ends of PVY-RNA showed that the PVY-type isolates resembled those reported in 1996 from Manitoba. These isolates are designated as PVY. In view of the increased incidence of PVY in one production area, seed tubers imported from other provinces of Canada and the neighboring United States were analyzed for PVY. The PVY was detected in imported seeds from Minnesota, Montana, and North Dakota.