Combining a host gene and a tobacco vein mottling virus coat protein gene for broad and effective resistance to potyviruses in tobacco (Nicotiana tabacum L.)

Over 100 transgenic tobacco lines in five genetic backgrounds were transformed with the tobacco vein mottling virus (TVMV) coat protein (CP) gene. Transgenic lines were initially tested for their reaction to inoculation with a TVMV systemic strain (TVMV-S) and a potato virus Y common strain (PVY-O). Of the 104 TVMV CP lines 60% were classified as resistant to PVY-O, whereas only 30% of these same lines were resistant to TVMV-S. A subset of six PVY-O-resistant transgenic lines and four control lines were tested for their reaction to a local isolate of TVMV, tobacco etch virus (TEV) and five isolates of PVY. The same ten lines were also tested for responses to a serial dilution of inoculum for two PVY isolates, PVY-KY1 and PVY-NN. Transgenic lines carrying an endogenous resistance gene known as Virgin A mutant (VAM) had greater resistance and a broader spectrum of resistance than did transgenic lines without the VAM gene. This additive effect of the endogenous resistance gene and coat protein-mediated resistance (CPMR) was not overcome by the highest inoculum concentration. The results indicate that the additive effect of the VAM gene and CPMR could extend the effectiveness of CPMR in controlling potiviruses. These findings could have important implications for plant improvement programs using CPMR against potyvirus diseases.