Changing Strain Composition of
Potato virus Y (PVY) in the U.S. Potato
By Alexander V. Karasev, Ph.D.
Professor of Plant Virology
University of Idaho
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Potato virus Y (PVY) is the most serious problem facing the seed potato industry in the United States and the main cause for rejection of seed potato lots. In addition to affecting seed potato production, PVY reduces yields of commercial potato crops and may reduce the quality of tubers because of necrotic reactions in susceptible cultivars. PVY is a complex of strains with a range of symptoms in different potato cultivars and different environments. During the past 10 years, a distinct shift has been observed in the prevalence of recombinant PVY strains (associated with tuber damage) in the U.S. potato. This shift in strain prevalence resulted in the virtual disappearance of the nonrecombinant, ordinary strain, PVYO, dominant in the United States until 2012 and the rise of two recombinant strains,
PVYN-Wi and PVYNTN, which together represent more than 90% of all PVY isolates now circulating in potato. This PVY
strain-prevalence shift is related to the release of new potato cultivars exhibiting strain-specific resistance mainly against PVYO. These changes in PVY strain composition in potato fields have important consequences for potato certification, potato breeding programs, and diagnostic laboratories.