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Resistance

Plasmid-Mediated Resistance to Streptomycin in Xanthomonas campestris pv. vesicatoria. G. V. Minsavage, Department of Plant Pathology, University of Florida, Gainesville 32611; B. I. Canteros, and R. E. Stall. Department of Plant Pathology, University of Florida, Gainesville 32611. Phytopathology 80:719-723. Accepted for publication 26 January 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-719.

Fifty-five percent of 548 strains of Xanthomonas campestris pv. vesicatoria from pepper and tomato grew on media containing 100 µg/ml of streptomycin sulfate. A DNA library of resistant strain BV5-4a was constructed in the cosmid vector pLAFR3. A clone containing an insert of 17 kb conferred resistance to streptomycin after conjugative transfer to a sensitive strain of X. c. vesicatoria. The 4.9-kb insert DNA of a subclone encoding wild-type resistance to streptomycin was labeled and used as a probe in Southern hybridization analyses. The streptomycin-resistance locus was found to be on a plasmid of 68 kb. The subclone DNA hybridized with enzyme-digested genomic or plasmid DNA of three of 17 other resistant strains of X. c. vesicatoria as well as with the DNA from streptomycin-resistant strains Psp 34 and Psp 36 of Pseudomonas syringae pv. papulans. No hybridization occurred with DNA from Erwinia amylovora strain UCBPP 829 or P. cichorii strain Pc 83-1, which also are resistant to streptomycin.