Factors influencing PVY development and disease expression in three potato cultivars

Abstract

Studies were performed to investigate factors affecting symptom expression of potato virus Y infection in three potato cultivars, Russet Norkotah, Shepody, and Red LaSoda. Quantitative enzyme-linked immunosorbent assay (ELISA) results revealed few differences in the relative virus titer among cultivars tested. Potato virus Y (PVY) titers developed as rapidly in Russet Norkotah as in Shepody and Red LaSoda. Additional studies were performed to determine the effect of light intensity and infections of PVY and potato virus X (PVX), alone and in combination, on the expression of mosaic symptoms in these three cultivars. Low light intensity (270-330 uE/m2/sec) significantly increased plant heights and severity of mosaic disease among the cultivars compared to high light intensity (100-200 uE/m2/sec). PVX and PVY, as well as the combination of PVX and PVY in the same plant, decreased plant height compared to the uninoculated (healthy) controls. Low light intensity and dual infections of PVX and PVY significantly increased mosaic disease severity in Shepody and Red LaSoda, but not in Russet Norkotah. Results of these studies refute the suggestion that Russet Norkotah is resistant to PVY infection since virus titers in this cultivar are similar to the known susceptible cultivars Shepody and Red LaSoda. These results further suggest that while Russet Norkotah is fully susceptible to infection by PVY, it resists symptom expression.