Induction of RNA-mediated Multiple Virus Resistance to Potato virus Y, Tobacco mosaic virus and Cucumber mosaic virus

Potato virus Y (PVY), Tobacco mosaic virus (TMV) and Cucumber mosaic virus (CMV) are three major tobacco viruses, which are widely spread and cause serious damage to tobacco. We sub-cloned the cDNA fragments from the 5' ends of the coat protein (CP) gene of PVY, TMV and CMV, with lengths of 200, 200 and 250 bp, respectively. The three cDNA fragments were cloned into one chimeric cDNA, and introduced into the binary vector pROKII in a way of inverted repeat which was supposed to form a hairpin RNA (hpRNA) after transcription. The corresponding construct pRHPTC was introduced into tobacco NC89 via Agrobacterium tumefaciens, and 1018 transgenic tobacco plants were obtained. Resistance assay indicated that up to 18% of the transgenic plants were immune to co-infection with PVY, TMV and CMV. Molecular analysis demonstrated that multiple virus resistance was RNA-mediated and stably inherited in T₂ progeny.