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Differential spread of Potato virus Y (PVY) strains in the field: implications for the rise of recombinant PVY strains in New Brunswick, Canada

Xianzhou Nie: Agriculture and Agri-Food Canada, Fredericton Research and Development Centre

<div><em>Potato virus Y</em> (PVY) is a major cause of yield and quality loss in potato crops worldwide. Multiple strains and substrains, including the common strain (PVY<sup>O</sup>), recombinant N:O strain (PVY<sup>N:O</sup>) and recombinant potato tuber necrosis (PVY<sup>NTN</sup>) strain have been recognized. In a survey carried out in 2009 in New Brunswick (NB), Canada, PVY<sup>O</sup> was the predominant strain followed by PVY<sup>N:O</sup> and PVY<sup>NTN</sup> were widespread in potato seed lots. Recently, populations of PVY strains have shifted dramatically toward recombinant strains. A continuous survey of PVY strains in commercial fields of NB from 2009 to 2016 and five field trials tracking PVY spread in the province were conducted to study the current status of PVY strains and their relative rates of spread. PVY<sup>O</sup> dropped from 82% of infections in 2010 to 14% in 2016, replaced mostly by PVY<sup>NTN</sup> (64%) and PVY<sup>N:O</sup> (22%). In field trials with potato cultivars Russet Burbank and Goldrush, PVY<sup>NTN </sup>spread most effectively compared to PVY<sup>N:O</sup> and PVY<sup>O</sup>. Strain-specific PVY spread varied with the potato cultivar, possibly due to selective PVY<sup>O</sup> hypertensive resistance in Goldrush, mostly expressed at the plant-to-plant transmission level with little difference in transduction to tubers in infected plants.</div>