Characterization of potato potyvirus Y (PVY) isolates from seed potato batches. Situation of the NTN, Wilga and Z isolates

A collection of 38 PVY isolates from seed potato batches, originating from several Western European countries, was characterized by using current biol ogical, serological and molecular tools differentiating PVY strains and gro ups. The correlation between the three kinds of tests was good but not abso lute. No single serological or PCR method was able to discriminate among th e five isolate groups found. Twenty-nine isolates belonged to the PVYN stra in and six to the PVYO strain. No PVYC was found. Two other isolates reacte d serologically like PVYO, but were unable to elicit a hypersensitive respo nse from the Ny(tbr) gene and probably represent the PVYZ group. At the mol ecular level, these two isolates showed a combination of both PVYO and PVYN and could be recombinants of these strains. Another isolate reacted serolo gically like PVYO, but induced vein necrosis in tobacco, like PVYN-Wilga. S ome PVYN isolates caused tuber ring necrosis in glasshouse conditions. Thes e might belong to the PVYNTN group. The PVYNTN, PVYN-Wilga and PVYZ groups probably represent pathotypes within strains PVYN and PVYO, respectively. T he present study also confirms previous reports showing a high genetic vari ation at the 5' end within the PVYN strain.