Potato virus Y in Seed Potatoes Sold at Garden Stores in Western Washington: Prevalence and Strain Composition

Between 2016 and 2018, a study was conducted to evaluate the prevalence and significance of Potato virus Y (PVY) present in seed potatoes distributed through garden stores in western Washington. Seed potatoes, particularly those exhibiting symptoms of cracking possibly caused by PVY, were purchased and grown-out in greenhouse tests. A relatively high incidence (47% in 2016; 26% in 2017; 29% in 2018) of the collections (15, 31, and 49 seed lots in total, respectively) produced plants that were confirmed by ELISA to be infected with PVY. Seed sold for organic production yielded approximately ten times more PVY infections than seed sold for conventional production. Strain typing revealed infections primarily by PVYO, PVYNTN, and PVYN-Wi. Mixed infections of PVYO/NTN and PVYO/N-Wi were detected a few times and no new or unusual PVY strains were found. These PVY strain types often were recovered from plants originating from cracked seed tubers, and the incidence of PVYN-Wi from cracked tubers increased (22% to 69%) during the study. PVYN-Wi remains an important constituent of the region’s PVY strain composition since its first detection in 2011. Garden enthusiasts and organic potato growers need more information about PVY to help mitigate the risk that PVY infected seed tubers could pose to commercial potato production fields.