Distribution and Characterization of Xanthomonas Strains Causing Bacterial Spot of Tomato in Indiana

Abstract

Over a 2-year period, samples of tomato suspected of being infected with bacterial spot were collected across Indiana and sent to the Purdue Plant and Pest Diagnostic Laboratory (PPDL). A total of 50 strains were collected over 2 years. An effort was made to collect from both fresh market and processing tomato fields (22 from fresh market, 25 from processing, and 3 unspecified). The PPDL screened samples for bacterial spot, and they isolated and confirmed the pathogen. The Xanthomonas isolates were then sent to Jeff Jones at the University of Florida to determine taxonomic identification, race determination, and sensitivity to copper at 50 ppm and streptomycin at 200 ppm. The majority of Xanthomonas strains collected (78%) were classified as X. perforans. The majority of the X. perforans strains were designated race T4. A total of 12% of strains were classified as X. gardneri, all of which were collected north of U.S. I-70, a route that bisects the state into approximately even halves. X. euvesicatoria was only observed on one sample. X. vesicatoria was not observed. Of all strains collected in Indiana, 84% were copper tolerant. In contrast, only 58% of the strains were insensitive to streptomycin.