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Epidemiology and pathogen diversity of Xanthomonas campestris pv. campestris in New York

Holly Lange: SIPS,Cornell University

<div>Black rot caused by the bacterium <em>Xanthomonas campestris </em>pv<em>. campestris</em> (Xcc) is often a serious disease of crucifers in New York, impacting yield and storage quality. We have followed the pathogen population in New York to determine its diversity, if it overwinters in weeds or crop residue, which control methods are most efficacious, and how currently grown cultivars differ in susceptibility over diverse seasonal weather patterns. Over 300 isolates have been collected, from 2004-2017, and tested for pathogenicity on cabbage as well as examined for diversity via multi-locus sequence analysis. Studies to identify the frequency of Xcc overwintering in NY and starting epidemics the following year have also been performed. Our findings show that new strains of Xcc enter NY each year, and while weeds can be hosts of Xcc, they are not a major source of inoculum. Copper-based products and plant activators are effective in slowing disease spread in the greenhouse and field. Additionally, resistant cultivars that were tested held up over cool/wet or hot/dry seasons with warmer seasons being more conducive to infection. Increased knowledge of the epidemiology, population diversity, and products that control this bacterium have improved management strategies for growers and identified future areas for research.</div>