ISHS Acta Horticulturae 695: I International Symposium on Tomato Diseases
BACTERIAL SPOT - WORLDWIDE DISTRIBUTION, IMPORTANCE AND REVIEW |
| Authors: | J.B. Jones, G.H. Lacy, H. Bouzar, G.V. Minsavage, R.E. Stall, N.W. Schaad |
| Abstract:
Bacterial spot disease on tomato is a major problem in tropical, subtropical, and temperate climates. Variation within this organism has been well documented. Two distinct groups, i.e., A and B, were identified in the early 1990s based on phenotypic and genotypic tests. These two groups were determined to be distributed widely throughout the world. The two groups were placed in Xanthomonas axonopodis pv. vesicatoria and X. vesicatoria, respectively in 1995. Following the identification of these two groups, two additional groups, C and D, have been identified that are pathogenic to pepper, tomato, or both hosts. The C group was originally isolated in 1991 and has more recently been found in many tomato production regions in the United States and in Mexico. Group D strains originally isolated in Costa Rica were determined to be closely related to X. gardneri, isolated by Sutic in Yugoslavia in 1957. The group D strains have been identified more recently in Michigan and in Brazil. Based on DNA homology experiments the C and D strains were determined to have less than 70% DNA similarity with strains from the other groups, with the type strain of X. axonopodis, and with the currently classified species within Xanthomonas. We have proposed that the C group strains be designated X. perforator sp. nov. and that the D group strains, which had less than 70% DNA similarity with any of the Xanthomonas species and which never had taxonomic status be named X. gardneri to reflect the specific epithet proposed by Sutic in 1957. Tomato races designated T1 (group A strains), T2 (group B strains) and T3 (group C strains) have been identified based on differential reactions with a group of tomato genotypes. Recently, two new races, T4 and T2, were identified in Florida. These races are group C strains with mutations in the avrXv3 and the avrXv3 and avrXv4, respectively. | |
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