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Weeds like survival niches of Xanthomonas campestris pv. campestris

Karine Teles Girotto: São Paulo State University

<div>Weeds compete with crops for resources and are host pathogens such as the bacterium <em>Xanthomonas campestris</em> pv. <em>campestris</em> (Xcc), causal agent of crucifer black rot. The aim of this study was to identify symptomatic hosts and epiphytic colonization in the weed phylloplane. Weeds were collected in a crucifer production area with a history of black rot in the municipality of Pardinho, São Paulo, Brazil and sent to the laboratory. Isolation of the symptomatic plants and the processing of the phylloplane samples were performed, plated in NSCAA semi-selective medium, incubated (28 °C / 72h) and the characteristics of colonies were observed. <em>Raphanus raphanistrum</em>, <em>Bidens pilosa</em> and <em>Sonchus oleraceus</em> were confirmed as hosts and the presence of the bacterium was verified in the phylloplane of <em>Eleusine indica</em>, <em>Solanum americanum</em>, <em>Ageratum conyzoides</em>, <em>Commelina</em> spp., <em>Galinsoga parviflora</em> and <em>Leonurus sibiricus</em>. The identity of the isolates was confirmed by PCR with the specific primers HrcCF2 and HrcCR2, and by pathogenicity test. Based on the results, it is recommended the eradication of these weed species in areas with black rot occurrence for inoculum reduction.</div>