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POSTERS: Population Biology Genetics I

P-557 - Population flux in tomato bacterial spot species following a two-year outbreak and identification of a new species Xanthomonas oklahomensis sp. nov.

Monday, August 4, 2025
4:30 PM - 5:15 PM HST
Location: Exhibit Hall 3
Abstract Text:

Bacterial spot of tomato (BST) is an important disease of tomato caused by Xanthomonas euvesicatoria pv. euvesicatoria (Xee), X. euvesicatoria pv. perforans (Xep), X. hortorum pv. gardneri (Xhg) and X. vesicatoria (Xv). Phenotypic and genomic characterization of these species have improved understanding of species identity, diversity and evolution. The identity and Xanthomonas species causing BST in Oklahoma is not well characterized. Following reports of epidemics of tomato diseases in tomato fields in central and eastern Oklahoma in 2018 and 2019, field surveys were carried out in 29 field sites across 13 counties. Strains recovered in these surveys, alongside strains recovered in previous years, were characterized to identify  their races  on  tomato/pepper race differential lines, copper and streptomycin sensitivities, amylolytic activity and genome-based characterization. Phenotypic and whole genome characterization identified strains exhibiting differences in amylolytic activity, streptomycin and copper sensitivities and race profiles, with majority of strains identified as Xee and Xep, including an apparent displacement of Xee by Xep and a shift from T3 to T4 race within two years. The study also identified  xanthomonad strains that did not cause BST,  including a new species X. oklahomensis sp. nov. These results are important in understanding the species and epidemiology of strains causing bacterial of tomato in Oklahoma.