RAPID PRODUCTION AND FIELD TESTING OF HOMOZYGOUS TRANSGENIC TOBACCO LINES WITH VIRUS-RESISTANCE CONFERRED BY EXPRESSION OF SATELLITE RNA AND COAT PROTEIN OF CUCUMBER MOSAIC-VIRUS

A procedure for the fast production of homozygotic transgenic plants w as developed. Leaf discs of haploid tobacco plants from anther culture s were transformed with a chimaeric vector containing coat protein (CP ) and satellite RNA (Sat-RNA) genes from cucumber mosaic virus (CMV). One-hundred-and-twelve Kanamycin-resistant transformed haploid plants were subjected to selection based on the expression of both CP and Sat -RNA. Eighty-nine transgenic plants expressing both genes were selecte d and tested for their resistance to CMV by inoculation with high conc entration of CMV (200 mu g ml(-1)). Only five plants showed no symptom s of viral infection 30 days after inoculation. These plants were then diploidized by colchicine treatment. Three homozygous diploid lines w ith high levels of resistance to CMV were obtained after only one gene ration. The three transgenic lines were further tested under field con ditions. The results showed that the progenies of these transgenic lin es were homozygous and were highly resistant to CMV under natural fiel d infection and manual inoculation conditions.