Molecular and Biological Characterization of Recombinant Isolates of Circulating in Potato Fields in Mexico.

(PVY) is a significant threat to potato () production in Mexico. The presence of recombinant strains of PVY circulating in potato has been reported in the country, but no systematic study on the genetic diversity of PVY in potato and prevalence of PVY strains has been conducted yet. We report on a series of surveys in seed potato production areas in two states in Mexico, namely, Chihuahua and Jalisco, between 2011 and 2019. PVY was detected through the period of nine years in multiple potato cultivars in both states, often remaining asymptomatic in the most popular cultivars, such as 'Fianna' and 'Agata'. When typed to strain, all PVY samples studied were found to have N-serotype, and were all identified molecularly as isolates of the same recombinant strain, PVY. Five of these PVY isolates were tested on tobacco (), where they induced vein necrosis supporting the molecular typing. This identification was also confirmed biologically on differential potato cultivars, where one PVY isolate from the 2013 survey triggered the hypersensitive resistance conferred by the gene in the cv. Maris Bard. Seven of these Mexican PVY isolates, collected between 2013 and 2019, including two PVY isolates from potato tubers exhibiting potato tuber necrotic ringspot disease, were subjected to whole genome sequencing and found to show a typical PVY recombinant structure. When subjected to phylogenetic analysis, Mexican PVY sequences clustered in more than three separate clades, suggesting multiple introductions of PVY in the country. The wide circulation of the PVY strain in Mexican potato should be considered by potato producers, to develop mitigation strategies for this PVY strain associated with tuber necrotic symptoms.