Role of hairy nightshade Solanum sarrachoides (Sendtner) in the transmission of Potato virus Y (PVY) strains by aphids and characterization of the PVY strain reactions on Solanum tuberosum (L.)

Potato virus Y (PVY) (Potyviridae: Potyvirus ), is the most economically important virus affecting potato seed and tuber commercial production in the Pacific Northwest (PNW) of the USA. The complexity of the PVY-potato pathosystem is affected by the presence of several virus strains that differ in their ability to produce tuber necrosis, and the presence of an alternate host that increases the amount of inoculum in potato fields. Solanum sarrachoides (Sendtner), an invasive weed from South America present in PNW potato agro-ecosystems, serves as reservoir of PVY and its most efficient vectors, the green peach aphid, Myzus persicae (Sulzer), and the potato aphid, Macrosiphum euphorbiae (Thomas). The role of S. sarrachoides as vector and virus reservoir in PVY epidemiology was investigated through a series of laboratory and field experiments. A study of symptom development and titer accumulation of PVY in S. sarrachoides revealed the host susceptibility to infection by different strains of PVY. Greenhouse transmission studies revealed that PVY-infected S. sarrachoides increased the transmission rate of PVY necrotic strains by M. persicae and M. euphorbiae. A field study experimentally demonstrated that the presence of PVY-infected S. sarrachoides increased the transmission of PVY in potato plots by M. persicae, M. euphorbiae and Rhopalosiphum padi (L). A comparative study between mechanical and aphid virus inoculation of three potato cultivars with PVY revealed that necrotic strains were more efficiently transmitted by M. persicae than the non-necrotic strain, and upon virus inoculation these strains tended to reach higher virus concentrations. Upon PVY aphid-inoculation in S. sarrachoides, PVYNTN, a necrotic strain, reached higher concentrations than PVYO, a non-necrotic strain, at different sites in the plant.