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 (PVYO) and tobacco veinal necrosis strains (PVYN/NTN) indicated that 37.5% contained PVYO and 63.5% contained PVYN-type isolates. Analysis of the PVYN-type samples using three monoclonal antibodies (MAbs) showed that all reacted with only the PVYO MAbs and not with the PVYN-specific MAb. Partial nucleotide sequences of both ends of PVY-RNA showed that the PVYN-type isolates resembled those reported in 1996 from Manitoba. These isolates are designated as PVYN:O. In view of the increased incidence of PVYN:O in one production area, seed tubers imported from other provinces of Canada and the neighboring United States were analyzed for PVYN:O. The PVYN:O was detected in imported seeds from Minnesota, Montana, and North Dakota.