Transmission of potato virus Y strains from single, two-way, and three-way strain mixtures by the aphid vector Myzus persicae (Sulzer) on potato

Potato virus Y (PVY) constrains potato production and seed tuber production in the USA and worldwide. PVY is transmitted by many different aphid species in a non-persistent manner; however, green peach aphid (GPA, Myzus persicae Sulzer) is the most efficient vector. An evolving concern of PVY in the United States is the recent emergence of necrotic strains (N, N:O, NTN, NA-NTN) relative to the ordinary strain (O). Mixtures of different PVY strains also have been observed in potato. GPA-mediated transmission studies were conducted to clarify transmission efficiency and strain specificity in single versus mixed-strain inoculum sources. Eight treatments of the experiment included single (PVY^O, PVY^N:O, PVY^NA-NTN), double (PVY^O+N:O, PVY^N:O+NA-NTN , PVY^O+NA-NTN ), and triple (PVY^O+N:O+NA-NTN ) strain mixtures as well as a sham inoculation. Transmission efficiency varied among treatments. GPA tended to transmit a single strain when the source mixture included O, but were more likely to transmit multiple strains when the source mixture did not include O. In the triple-mixture treatment, all dual combinations except N:O+NA-NTN were observed; however, we did not observe simultaneous transmission of all 3 strains. Regardless of strain combination, an apparent dominance of the O strain was observed. Apparent primacy of transmission of the O strain from strain mixtures suggests that differences in transmission efficiency for GPA may not be a contributing factor to the recent emergence of necrotic strains.