The effects of single and mixed PVY infections on vector efficiencies

North American seed potato producers continue to experience an unprecedented Potato virus Y (PVY) epidemic. Since 1997, 45% of potato seed lots entered into the Minnesota Seed Potato Certification Program winter grow-out have exceeded PVY tolerances. The greatest obstacle to managing this PVY epidemic is the increasing prevalence of the visually cryptic PVY strain N:O. In 2003, our virus survey detected PVY^N:O in 30% of PVY infected plants. PVY^N:O has become the dominant PVY strain in the North Central Plains, accounting for 56% and 75% of PVY infected plants tested in 2005 and 2007, respectively. Given the rapid increase in the prevalence PVY^N:O, we conducted experiments to determine whether PVY strains PVY^O, PVY^N:O, and PVY^mixed (infected with both PVY^O and PVY^N:O) differed in their transmission efficiencies by four key aphid vectors; Myzus persicae (green peach aphid), Aphis glycines (soybean aphid), Rhopalosiphum padi (bird cherry-oat aphid), and Acyrthosiphon pisum (pea aphid). Green peach aphid was the most efficient PVY vector (30%), followed by soybean aphid (12%), bird cherry-oat aphid (6%) and pea aphid (3%). Green peach aphid and soybean aphid transmitted all PVY strains equally. Pea aphid vector efficiencies were significantly higher from PVY^N:O (3%) and PVY^mixed (7%) acquisition sources than from PVY^O (0%). Bird cherry-oat aphid PVY transmission was significantly reduced, from 8% to 2%, when acquiring from a mixed source. This is the first report of PVY^O-PVY^N:Omixed infection effects on transmission efficiencies.