A 3RD TOMATO RACE OF XANTHOMONAS-CAMPESTRIS PV VESICATORIA

Strains of Xanthomonas campestris pv. vesicatoria were isolated from several tomato fields in Florida that differed from tomato race 1 (T1) strains commonly found in Florida. The strains produced a compatible reaction on tomato genotype Hawaii 7998 (H7998), were amylolytic and pectolytic, and were classified originally as T2 strains. However, these strains produced a rapid hypersensitive response when infiltrated into the tomato genotypes Hawaii 7981 (H7981), PI 126932, and PI 128216, whereas T2 strains produced a compatible reaction. In an experiment where electrolyte leakage was determined in leaflets of tomato cv. Bonny Best (compatible with ah tomato strains), H7998 (resistant to T1 strains), and the two PIs, a member of these new strains induced a rapid hypersensitive response in the three tomato genotypes, whereas a T2 strain did not. After low concentrations of bacteria were infiltrated into the mesophyll of leaflets of PI 126932, PI 128216, H7998, and cv. Waiter (compatible with all tomato strains), internal populations of the amylolytic, pectolytic Florida strain were reduced when tested in the first two genotypes but not in the latter two genotypes. Populations of the T1 strain were reduced only in H7998. These new strains are designated tomato race 3 (T3). When the T3 strains were compared with a representative group of T1 and T2 strains by fatty acid analysis and carbon substrate utilization patterns, the new T3 strains clustered distinctly from representative T1 and T2 strains. The evidence suggests the T3 strain is a recent introduction to Florida. An amylolytic, pectolytic strain isolated from seed grown in Thailand reacted similarly to the T3 strains on the tomato differentials. It also clustered with the T3 strains in the fatty acid and carbon substrate utilization dendrograms.