CHARACTERIZATION OF A PEPPER MILD MOTTLE TOBAMOVIRUS STRAIN CAPABLE OF OVERCOMING THE L-3 GENE-MEDIATED RESISTANCE, DISTINCT FROM THE RESISTANCE-BREAKING ITALIAN ISOLATE

Green pepper plants with the L-3 resistance gene usually develop necro tic lesions on leaves infected with a Japanese strain of pepper mild m ottle tobamovirus (PMMoV-J), A recently discovered strain, PMMoV-Ij, h as the ability to overcome L-3 resistance, Phytopathological responses of a variety of plant species to PMMoV-J and PMMoV-Ij were determined and the coat protein (CP) sequence comparisons revealed both amino ac ids 43 and 50 of PMMoV-Ij were unique, This led us to believe that sub stitutions at these residues would enable PMMoV-J to overcome L-3 resi stance, This was confirmed by Western blot (immunoblot) detection of P MMoV-J containing both point mutations in upper uninoculated leaves of resistant plants, Computer models suggest the critical residues in ov ercoming resistance lie in CP regions that putatively interact with ot her subunits. These results contribute to our understanding of the vir us's ability to circumvent plant resistance.