PROTECTION AGAINST CUCUMBER MOSAIC-VIRUS (CMV) STRAINS-O AND STRAINS-Y AND CHRYSANTHEMUM MILD MOTTLE VIRUS IN TRANSGENIC TOBACCO PLANTS EXPRESSING CMV-O COAT PROTEIN

Transgenic tobacco expressing the coat protein (CP) of cucumber mosaic virus strain O (CMV-O) showed a significant level of protection against CMV strains O and Y. When inoculum concentrations were increased, the transformants showed a stronger level of protection against CMV-O than against CMV-Y. The substitution of an amino acid residue between CMV-O and CMV-Y, which is presumed to change the conformation of CP, may reflect the difference in susceptibility to these viruses. Furthermore the transgenic tobacco plants showed a significant level of protection against chrysanthemum mild mottle virus, a member of the cucumo-virus group but with no serological relationship to CMV.