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Identification of Xanthomonads and Grouping of Strains of Xanthomonas campestris pv. campestris with Monoclonal Antibodies. A. M. Alvarez, Departments of Plant Pathology and Microbiology, University of Hawaii, Honolulu 96822; A. A. Benedict(2), and C. Y. Mizumoto(3). (2)(3)Departments of Plant Pathology and Microbiology, University of Hawaii, Honolulu 96822. Phytopathology 75:722-728. Accepted for publication 28 January 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/Phyto-75-722.

Monoclonal antibodies (MCAs) were produced that identified the genus Xanthomonas, distinguished Xanthomonas campestris pv. campestris (X.c. pv. campestris) from other pathovars of X. campestris, and grouped and subgrouped strains of X.c. pv. campestris. One antibody, X1, was specific for all 436 xanthomonads that were tested, but it did not react with 104 bacteria of 12 other genera that were tested. Only crucifer strains (X.c. pv. campestris and two strains of X.c. pv. armoraciae) reacted with one or more of three MCAs (X9, X13, and X17) whereas 192 xanthomonads of other species and pathovars failed to react with any of these MCAs. The 104 strains of other genera and species also failed to react with these antibodies. Two hundred X.c. pv. campestris strains from Hawaii, Georgia, California, and Thailand were divided into six groups based on reactions with five MCAs, and into subgroups based on these and other MCAs. Most (83%) strains were in groups 1, 2, and 5; however, the strains from Hawaii and Georgia, the largest sample sizes, were distributed differently among these groups. These MCAs may be applied as markers for rapid identification of X.c. pv. campestris strains and for tracing strains in epidemiological studies of black rot.