Sudden Shift in the Prevalent Race of Xanthomonas campestris pv. vesicatoria in Pepper Fields in Southern Florida. Ken Pohronezny, University of Florida, Institute of Food and Agricultural Sciences (IFAS), Everglades Research and Education Center, Belle Glade 33430. Robert E. Stall, Blanca I. Canteros, Melanie Kegley, Lawrence E. Datnoff, and Ramachandra Subramanya. University of Florida, IFAS, Department of Plant Pathology, Gainesville 32611; University of Florida, Belle Glade; and Pepper Research Inc., 980 S.E. 4th St., Belle Glade 33430. Plant Dis. 76:118-120. Accepted for publication 4 September 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0118.

In the spring of 1988, 89% of 97 strains of Xanthomonas campestris pv. vesicatoria isolated from naturally infected pepper plants in commercial fields in southern Florida were race 2 and 11% were race 3. During the 1989–1990 season, however, 84% of 118 strains isolated were race 1, 15% were race 2, and 1% were race 3. Race 1 was predominant again during 1990–1991, with 68% of 100 strains identified as race 1, 13% as race 2, 11% as race 3, and 8% as the tomato race of X. c. vesicatoria. Four of 97 and four of 118 strains were found to be resistant to 200 μg/ml of streptomycin in 1988 and 1989–1990, respectively. During 1990–1991, streptomycin resistance was recorded for 26 of the 100 strains collected. Copper tolerance was detected for 114 of the 118 strains during 1989–1990. Possible reasons for these shifts in populations of X. c. vesicatoria are discussed.