MODIFIED RESISTANCE OF SOLANUM-BREVIDENS TO POTATO-Y POTYVIRUS AND TOBACCO MOSAIC TOBAMOVIRUS FOLLOWING GENETIC-TRANSFORMATION AND EXPLANT REGENERATION

Infected plants of Solanum brevidens accumulate extremely low titres o f potato Y potyvirus (PVY) and moderate titres of tobacco mosaic tobam ovirus (TMV); but, in plants infected with both viruses, accumulation of PVY is enhanced, suggesting that TMV assists the cell-to-cell sprea d or replication of PVY. Cell-to-cell movement of TMV is mediated by t he virus-coded 30-kDa movement protein. In this study, S. brevidens wa s transformed with the 30-kDa gene of TMV-204. Systemic spread of the temperature-sensitive mutant TMV-Ls1 occurred in four transgenic lines carrying the 30-kDa gene sense construct at the non-permissive temper ature (33 degrees C) indicating expression of functional wild type 30- kDa protein capable of complementing defective movement functions of T MV-Ls1. PVY accumulation was enhanced in three of these lines, in four transgenic 'sense' lines in which no complementation of TMV-Ls1 occur red, in nine 'antisense' lines, two lines lacking the 30-kDa gene inse rt, and nine non-transgenic callus-derived lines. No detectable infect ion or systemic spread of TMV-204 occurred in most of the callus-deriv ed lines. Thus, enhanced accumulation of PVY and increased resistance to TMV appeared to be associated with tissue culture-induced changes r ather than the 30-kDa gene insert.