Potato virus Y Transmission Efficiency from Potato Infected with Single or Multiple Virus Strains

There has been a recent shift in the prevalence of Potato virus Y (PVY) strains affecting potato with the ordinary strain PVY^O declining and the recombinant strains PVY^NTN and PVY^N:O emerging in the United States. Multiple PVY strains are commonly found in potato fields and even in individual plants. Factors contributing to the emergence of the recombinant strains are not well defined but differential aphid transmission of strains from single and mixed infections may play a role. We found that the transmission efficiencies by Myzus persicae, the green peach aphid, of PVY^NTN, PVY^N:O, and PVY^O varied depending on the potato cultivar serving as the virus source. Overall transmission efficiency was highest from sources infected with three virus strains, whereas transmission from sources infected with one or two virus strains was not significantly different. Two strains were concomitantly transmitted by individual aphids from many of the mixed-source combinations, especially if PVY^O was present. Triple-strain infections were not transmitted by any single aphid. PVY^O was transmitted most efficiently from mixed-strain infection sources. The data do not support the hypothesis that differential transmission of PVY strains by M. persicae is a major contributing factor in the emergence of recombinant PVY strains in the U.S. potato crop.