COPPER-RESISTANT AND STREPTOMYCIN-RESISTANT STRAINS AND HOST DIFFERENTIATED RACES OF XANTHOMONAS-CAMPESTRIS PV VESICATORIA IN NORTH-CAROLINA

Copper- and streptomycin-resistant strains of Xanthomonas campestris pv. vesicatoria were detected in diseased pepper and tomato plants. In surveys of 32 noncontiguous fields during four growing seasons, 63% of 70 strains were copper resistant and 30% were resistant to at least 100-mu-g/ml of streptomycin. All streptomycin-resistant strains were copper resistant. Strains of pepper races 1, 2, and 3, as well as strains from the tomato group, were detected. All tomato strains, all pepper race 2 strains, and 50% of pepper race 1 strains were copper resistant. Streptomycin resistance was detected only in the tomato strains and pepper race 2 strains. All strains of race 3 from the field were copper and streptomycin sensitive. Of 65 strains pathogenic to pepper (cv. Early Calwonder), 55, 31, and 12% were races 1, 2, and 3, respectively. A strain was isolated that was pathogenic on Early Calwonder (Xcv 19) but elicited a hypersensitive response in the three near-isogenic lines of Early Calwonder. It is proposed that this strain be designated race 0.