Modified resistance of Solanum brevidens to potato Y potyvirus and tobacco mosaic tobamovirus following genetic transformation and explant regeneration

Abstract

Infected plants of Solanum brevidens accumulate extremely low titres of potato Y potyvirus (PVY) and moderate titres of tobacco mosaic tobamovirus (TMV); but, in plants infected with both viruses, accumulation of PVY is enhanced, suggesting that TMV assists the cell-to-cell spread or replication of PVY. Cell-to-cell movement of TMV is mediated by the virus-coded 30-kDa movement protein. In this study, S. brevidens was 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 temperature (33°C) indicating expression of functional wild type 30-kDa protein capable of complementing defective movement functions of TMV-Ls1. PVY accumulation was enhanced in three of these lines, in four transgenic ‘sense’ lines in which no complementation of TMV-Ls1 occurred, in nine ‘antisense’ lines, two lines lacking the 30-kDa gene insert, and nine non-transgenic callus-derived lines. No detectable infection or systemic spread of TMV-204 occurred in most of the callus-derived lines. Thus, enhanced accumulation of PVY and increased resistance to TMV appeared to be associated with tissue culture-induced changes rather than the 30-kDa gene insert.