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Potato virus Y evolves to overcome strain-specific resistance in potato: rapid shift to recombinant virus strains in the U.S. potato

Alexander Karasev: University of Idaho

<div><em>Potato virus Y</em> (PVY) exists as a complex of strains, including multiple recombinants. Recombinant strains have been spreading in the U.S. for the past several years, but the reasons behind this spread were not clear. To document and assess this spread between 2011 and 2017, strain composition of PVY isolates circulating in the Columbia Basin potato production area was determined from hundreds of seed lots of various cultivars. The proportion of non-recombinant PVY<sup>O</sup> isolates circulating in Columbia Basin potato dropped ten-fold during this period. This decrease in PVY<sup>O</sup> was concomitant with the two-fold rise of the recombinant PVY<sup>N-Wi</sup> strain incidence. Greenhouse and semi-field experiments suggested that hypersensitive resistance (HR) genes present in the most popular potato cultivars may be responsible for the selection against PVY<sup>O</sup> strain and for the concomitant spread of recombinants in potato fields.</div>