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Pathovar-Specific Monoclonal Antibodies for Xanthomonas campestris pv. oryzae and for Xanthomonas campestris pv. oryzicola. A. A. Benedict, Departments of Microbiology and Plant Pathology, University of Hawaii, Honolulu 96822; A. M. Alvarez, J. Berestecky, W. Imanaka, C. Y. Mizumoto, L. W. Pollard, T. W. Mew, and C. F. Gonzalez. International Rice Research Institute, Philippines, and Department of Plant Pathology and Microbiology, Texas A & M University, College Station 77843. Phytopathology 79:322-328. Accepted for publication 22 September 1988. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-322.

Monoclonal antibodies (mAbs) were produced that were specific for Xanthomonas campestris pv. oryzae. Monoclonal antibody Xco-1 reacted with all 178 tested strains of X. c. oryzae from diverse geographical locations, including strains isolated from the recent blight outbreak on rice in Texas and Louisiana. A second mAb, Xco-2, reacted with most (87%) strains of X. c. oryzae, which included all but one of 92 Philippine strains. A third mAb of X. c. oryzae (Xco-5) reacted only with the 29 strains from Texas and Louisiana, and not with any other strain of X. c. oryzae; however, Xco-5 also reacted weakly with strains of X. c. oryzicola. An mAb specific for X. c. oryzicola was generated. None of the mAbs reacted with 130 xanthomonads of other pathovars and species, including 11 epiphytic xanthomonads from rice leaves, or with 89 strains of other genera. Based on immunofluorescence and immunoelectron microscopy, these mAbs detected surface antigens. The Xco-1 and Xco-2 epitopes were heat-sensitive and heat-resistant, respectively, and the Xco-2 epitope was found in the lipopolysaccharide fraction. Culture conditions were critical for expression of the Xco-5 epitope.