CONTRIBUTION OF 4 RACES OF XANTHOMONAS-CAMPESTRIS PV VESICATORIA TO BACTERIAL SPOT IN BARBADOS

The size of typical lesions of bacterial spot on tomato and pepper fruits was used to assess the extent to which each race of Xanthomonas campestris pv. vesicatoria contributes to disease in the field. Lesions associated with race 1 strains of the pepper or tomato group only were significantly larger than those from which pepper-tomato group race 2 or race 3 strains were detected. Pepper-tomato group race 3 was isolated from the smallest lesions. Six strains from tomato were virulent on pepper carrying the Bs2 resistance gene to bacterial spot, and no pepper group strains were detected on tomato. Race 1 strains of the pepper or tomato group were also most abundant and were associated with more lesions on pepper and tomato than pepper-tomato group race 2 or race 3 strains. Mixtures of strains comprising pepper or tomato group race 1 and pepper-tomato group race 2 were obtained from 10 to 15% of lesions on pepper and 11 to 20% of lesions on tomato fruit.