Interactions among potato genotypes, virus strains, inoculation timing and method in the potato virus Y and green peach aphid pathosystem

Abstract                                                                           

Potato virus Y (PVY) is an economically important and reemerging pathogen of potato in North America. PVY infection reduces the yield and some necrotic and recombinant strains render the tuber unmarketable. Although the strain PVY^O is most prevalent in the United States, the necrotic and recombinant strains PVY^NTN and PVY^N:O are becoming more widespread. Most varietal screening is conducted via mechanical inoculation; however, aphid inoculation is the primary means by which virus is transmitted in the field. The objective of this study was to examine infection rates in aphid-inoculated and mechanically inoculated plants, comparing (1) two potato genotypes (Yukon Gold, A98345-1), (2) three PVY strains (PVY^O , PVY^N:O, PVY^NTN), and (3) two growth stages at inoculation time (pre- vs. post-flowering). Plant infection status was determined via DAS-ELISA. Yukon Gold was more susceptible than A98345-1 to PVY. The rank order of overall infection rate from mechanical inoculation for Yukon Gold was PVY^O > PVY^N:O > PVY^NTN, and for A98345-1 was PVY^N:O > PVY^O ≈ PVY^NTN. Overall infection rate from aphid inoculation did not differ significantly among genotype and strain combinations. In most instances, infection rate was higher for mechanical inoculation compared to aphid inoculation. Infection rate was higher in both genotypes for pre-flowering inoculation relative to post-flowering inoculation, indicating both genotypes exhibit age-based resistance to PVY. Implications of these findings will be discussed.