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 tra nsformed with the tobacco vein mottling virus (TVMV) coat protein (CP) gene. Transgenic lines were initially tested for their reaction to in oculation with a TVMV systemic strain (TVMV-S) and a potato virus Y co mmon strain (PVY-O). Of the 104 TVMV CP lines 60% were classified as r esistant 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 TVM V, tobacco etch virus (TEV) and five isolates of PVY. The same ten lin es were also tested for responses to a serial dilution of inoculum for two PW isolates, PVY-KY1 and PVY-NN. Transgenic lines carrying an end ogenous resistance gene known as Virgin A mutant (VAM) had greater res istance and a broader spectrum of resistance than did transgenic lines without the VAM gene. This additive effect of the endogenous resistan ce gene and coat protein-mediated resistance (CPMR) was not overcome b y the highest inoculum concentration. The results indicate that the ad ditive effect of the VAM gene and CPMR could extend the effectiveness of CPMR in controlling potiviruses. These findings could have importan t implications for plant improvement programs using CPMR against potyv irus diseases.