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Whole genome sequence analysis of Xanthomonas perforans shows widespread recombination events

Sujan Timilsina: Department of Plant Pathology, University of Florida

<div>Bacterial spot is an important disease of tomato in the United Stated caused by multiple <em>Xanthomonas </em>species. In Florida, this disease is caused by <em>X. perforans</em> (<em>Xp</em>). Over the last 15 years, significant changes have occurred in <em>Xp</em> strains isolated from Florida, including shifts in bacterial races, loss of bacteriocins, and changes in effector profiles. Preliminary phylogenetic and genomic studies have identified recombination events between <em>X. euvesicatoria</em> (<em>Xe</em>) and <em>Xp</em>. Different phylogenetic groups within <em>Xp </em>appear to have differing patterns of recombination. Our objective was to analyze the extent and role of genetic exchange from <em>Xe</em> to <em>Xp </em>strains. We used whole genome sequences of <em>Xp</em> strains collected from the United States between 1991 and 2016. A core gene multilocus sequence analysis identified genes present in all <em>Xp</em> strains. Comparing core genes against reference strains <em>Xe</em> 85-10 and <em>Xp</em> 91-118 identified allelic variation specific to <em>Xe</em> and <em>Xp</em>, respectively. Results show that genetic exchange is distributed throughout <em>Xp</em> genomes and includes housekeeping and effector genes. Histidine kinase and TonB receptors were among the genes observed to have recombined in multiple genetic groups. These observations define the extent of genetic exchange driving recent <em>Xp</em> evolution.</div>