IMMUNITY TO INFECTION BY POTATO VIRUS Y AND POTATO VIRUS X IN A Solanum phureja - S. stentomum HYBRID POTATO POPULATION

Abstract

A random sample of 6000 individuals from a recombinant Solanum phureja - S. stentomum hybrid population and 250 individuals of Solanum phureja were twice inoculated with potato virus Y (PVY) strain “o” using the air brush technique. Symptomless seedlings were field transplanted for further evaluation and 1508 seedlings were judged to be resistant to PVY (33%). At harvest, a mild selection pressure for tuber appearance was applied and 602 clones were selected.Selected clones were re-evaluated for PVY resistance in the greenhouse: twice inoculated with PVY, tested by ELISA (Enzyme-linked immunosorbent assay), graft-inoculated with tobacco PVY infected scions, and subjected to a second ELISA test. To assess immunity to infection by PVY, the ELISA negative clones were bioassayed using tobacco cv. “Burley 21” as a plant indicator. We identified 224 PVY immune clones (4.8%).Simultaneously, the first year PVY selected clones were twice inoculated with U.S. common strain of potato virus X (PVX). Clones free of PVX symptoms were tested by ELISA. Negative clones were re-inoculated with PVX and symptomless clones were re-tested by ELISA. To assess immunity to infection by PVX, negative clones were bioassayed using Gomphrena globosa as a plant indicator. We identified 7 immune (1.3%); 4 highly resistant and 4 resistant clones. Eight clones showed high levels of resistance to both PVY and PVX (high resistance to immunity).