Survival of Xanthomonas campestris pv. vitians on lettuce in crop debris, irrigation water, and weeds in south Florida
2018
Fayette, Joubert | Jones, Jeffrey B. | Pernezny, Kenneth | Roberts, Pamela D. | Raid, Richard
Bacterial leaf spot of lettuce, caused by Xanthomonas campestris pv. vitians (Xcv), can be a disease of economic importance but it occurs sporadically in production fields in Florida. We investigated the role of weeds, irrigation water, and crop debris as potential inoculum sources for Xcv. Detection and identification of Xcv was facilitated using semi-selective media and PCR with two primers pairs. During field outbreaks of the disease, epiphytic populations of Xcv were detected on 13 weed species belonging in the Asteraceae, Amaranthaceae, Aizoaceae, Chenopodiaceae, Portulacaceae, Solanaceae, and Malvaceae families. In greenhouse assays, Xcv epiphytic populations on 12 weed hosts varied greatly. Bacterial leaf spot-like symptoms developed on Sonchus oleraceus and significantly higher populations of Xcv were recovered from this weed. Bacteria were also recovered from surface irrigation water monitored during a 4-month period covering two growing seasons at three commercial sites. In two seasons of survival studies on crop debris, Xcv was recovered up to 1 month after placement of diseased tissue on the soil surface but not detected in tissue buried 15 or 30 cm beneath the soil surface. Therefore, weeds and surface irrigation water may play a role in the survival of Xcv whereas crop debris may be limited as an inoculum source during the fallow period in Florida.
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