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Molecular Plant Pathology

Differentiation of Genomic Structure by rep-PCR Fingerprinting to Rapidly Classify Xanthomonas campestris pv. vesicatoria. Frank J. Louws, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824, Current address: Center For Microbial Ecology/MSU-DOE Plant Research Laboratory, Rm. 306, Plant Biology Bldg., Michigan State University, East Lansing 48824; Dennis W. Fulbright(2), Christine Taylor Stephens(3), and Frans J. de Bruijn(4). (2)(3)Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; (4)MSU-DOE Plant Research Laboratory and Department of Microbiology, Michigan State University, East Lansing 48824; (2)(4)NSF Center for Microbial Ecology, Michigan State University, East Lansing 48824. Phytopathology 85:528-536. Accepted for publication 27 January 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/Phyto-85-528.

DNA primers corresponding to repetitive extragenic sequences (repetitive extragenic palindromic [REP], enterobacterial repetitive intergenic consensus [ERIC], and BOX element [BOX1A] sequences) and polymerase chain reaction (rep-PCR) were used to generate complex fingerprint patterns that identified four distinct genotypes among strains classified as Xanthomonas campestris pv. vesicatoria. After agarose gel electrophoresis, these genotypes were easily differentiated from each other by comparing the migration rates of 60 or more bands generated with rep-PCR. Representative strains of each genotype were pathogenic to tomato and/or pepper. We performed rep-PCR on numerous strains that have been included in previous studies, and our observations using the simple, rapid procedure of rep-PCR were consistent with the polyphasic approaches published by others. The majority of strains belonged to two previously described groups, A and B. Group A strains originated from tomato or pepper. Most of these strains proved to be negative in starch hydrolysis and pectolytic activity tests. All group A strains were relatively homogeneous with regard to their rep-PCR fingerprint patterns. Group B strains originated primarily from tomato and were positive for starch hydrolysis and pectolytic activity. Numerous rep-PCR fingerprint polymorphisms distinguished six patterns or lineages in group B. Group B strains comprised an important component of the tomato spot complex in the Northcentral tomato production region of North America. Three strains comprised two additional genotypes and were clear outliers compared to strains classified as group A or B. Interestingly, based on rep-PCR genomic fingerprint patterns, two of the nongroup A/B strains shared numerous bands of similar mobility with strains pathogenic for cabbage, classified as X. c. pv. campestris, suggesting that these two solanaceous strains are closely related to the cabbage pathogen.

Additional keywords: bacterial spot, genetic diversity, integrated disease management, population structure, strain identification.