Disease Note.

First Report of Pepper Race 6 of Xanthomonas campestris pv. vesicatoria, Causal Agent of Bacterial Spot of Pepper. F. Sahin, Department of Plant Pathology, The Ohio State University, OARDC, Wooster, OH 44691. S. A. Miller, Department of Plant Pathology, The Ohio State University, OARDC, Wooster, OH 44691. Plant Dis. 79:1188. Accepted for publication 18 September 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-1188C.

During 1993 to 1994, a survey of commercial pepper fields and home gardens was conducted in Ohio and several neighboring states to determine the prevalence of different races of the bacterial spot pathogen, Xanthomonas campestris pv. vesicatoria (Xcv). Bacterial strains were identified as Xcv based on morphology, growth on yeast dextrose carbonate (YDC) medium and CKTM (2) semi-selective medium, biochemical and nutritional tests, hypersensitive reaction (HR) on tobacco, fatty acid methyl ester (FAME) analysis, and pathogenicity on pepper and tomato. The strains were characterized by the following criteria: reaction on pepper and tomato Xcv race differential lines (1), ability to degrade starch and pectin, composition of fatty acids (FAs), reaction to a panel of monoclonal antibodies (MAbs Xv 1, 5, 6, 8, 10, 15, 21, and 30) (1), and sensitivity to copper and streptomycin. Of the 76 strains isolated during that period and identified as Xcv, one strain isolated from pepper in Huron County, OH, in 1993 did nol cause a hypersensitive response on any of the three pepper race differential lines (near-isogenic derivatives of var. Early Calwonder). This strain, Xcv 17b, is a new, previously unde-scribed race, designated pepper race 6. All of the other Xcv pepper races cause hypersensitivity on at least one of these lines Strain Xcv 17b was highly aggressive on the Xcv-susceptible variety Marengo, and was also pathogenic on processing tomato cultivar OH8245. It induced an HR on tomato genotype Hawaii 7998, placing it in the Xcv tomato race 1 group. Its FAME profile closely matched those of the representative Xcv strains in the TSBA library (Microbial ID, Inc., Newark, DE). It was not amylolytic or peclolytic. Furthermore, it was sensitive to copper (30 ?g/ml), but resistant lo streptomycin (100 ?g/ml). Xcv 17b did not react positively with any of the eight Xcv-specific MAbs tested. This is the first report of the occurrence of a race of Xcv capable of overcoming all three of the known sources of resistance in pepper to this pathogen.