Multilocus Sequence Analysis of a Worldwide Collection of Xanthomonas Strains, Causing Bacterial Leaf Spot

Four distinct Xanthomonas species are responsible for bacterial leaf spot of tomato. Eighteen Xanthomonas strains collected from different geographical locations around the world were characterized to determine their phylogenetic relationships to other xanthomonads based on multilocus sequence analysis of the lepA, lacF, fusA, gapA, gltA and gyrB house-keeping genes. Phylogenetic analysis based on Maximum Likelihood and Bayesian methods provided congruent placement of the strains within their respective species. Strains of X. euvesicatoria originating from the United States, Barbados, Mexico and Australia showed the most variation between the amylolytic and non-amylolytic strains. Strains of X. vesicatoria originating from South America and New Zealand showed slight sequence variation, while X. perforans strains from Mexico, Thailand and the United States were highly conserved except for a recently isolated strain from pepper. Strains of X. gardneri isolated from Costa Rica and former Yugoslavia exhibited no sequence variation among the six characterized housekeeping genes.