FIELD-RESISTANCE OF TRANSGENIC BURLEY TOBACCO LINES AND HYBRIDS EXPRESSING THE TOBACCO VEIN MOTTLING VIRUS COAT PROTEIN GENE

Fifty transgenic lines expressing the tobacco vein mottling virus (TVM V) coat protein (CP) gene in five genetic backgrounds were evaluated u nder field conditions for response to mechanic inoculation with TVMV, tobacco etch virus (TEV) and potato virus Y (PVY). TVMV CP transgenic lines conferred resistance to TVMV, TEV and PVY under field conditions . Combining two strategies, coat protein-mediated resistance (CPMR) co upled with an endogenous resistance gene (Virgin A Mutant, VAM) signif icantly extended the range and magnitude of virus resistance and provi ded a potential valuable new source of protection against potyviruses. CP transgenic lines lacking the VAM gene had high resistance to TEV, medium resistance to PVY, and a recovery phenotype to TVMV. A series o f hybrids involving transgenic lines were generated and tested under f ield conditions for response to virus inoculation. One copy of TVMV-CP gene presented in lines homozygous for the VAM gene provided effectiv e resistance to all three potyviruses. These studies also suggested th at selection of a suitable recipient genotype was critical and that he ld evaluation was necessary in order to select elite resistant transge nic lines. Engineering viral CP genes into genotypes possessing some l evel of virus resistance could be critical to achieve an effective lev el of resistance.