Bacterial spot caused by spp. is a significant disease that challenges pepper growers worldwide and is particularly severe in a hot and humid environment. Understanding the pathogen’s population biology is critical for sustainable disease management. The goal of this study was to characterize the species, race, and bactericide sensitivity of bacterial spot-associated Xanthomonas collected from pepper in Florida. A survey of pepper production fields in Southwest Florida between 2019-2021—covering two counties, eight farms, and two transplant facilities— resulted in the isolation of 542 Xanthomonas euvesicatoria (X. euvesicatoria) and 35 Xanthomonas perforans (X. perforans) strains. Four races were identified on pepper, of which most strains were race P1 (42%), race P6 (26%), race P3 (24%), and less common was race P4 (8%). All X. perforans strains were characterized as race P1 and showed a compatible reaction on tomato. Sixty-two and 96% of strains were sensitive to copper sulfate and streptomycin, respectively. One farm that did not use copper to manage the disease contained only copper-sensitive strains and was the only farm with race P3 strains. Strains were assayed for starch hydrolysis activity of which a third of X. euvesicatoria strains were strongly amylolytic, a characteristic not typically observed in X. euvesicatoria. All X. perforans strains produced bacteriocins against X. euvesicatoria in-vitro. The Xanthomonas population causing bacterial spot-on pepper in Southwest Florida is diverse and dynamic; thus, regular monitoring provides pertinent information to plant breeders and growers for designing disease management strategies. Key words: Bacterial-spot, Xanthomonas, pepper, races, copper, streptomycin, amylase, bacteriocin

Xanthomonas perforans (X. perforans)—the dominant causal agent of bacterial leaf spot of tomato—is an emerging pathogen of pepper, indicative of a potential host expansion across the Southeastern United States. However, studies of the genetic diversity and evolution of X. perforans from pepper remain limited. In this study, the whole genome sequences of 35 X. perforans strains isolated from pepper from 4 fields and 2 transplant facilities across Southwest Florida between 2019-2021 were used to compare genomic divergence, evolution, and variation in Type III secreted effectors. Phylogenetic analysis based on core genes revealed that all 35 X. perforans strains formed one genetic cluster with pepper and tomato strains from Alabama and Turkey and were closely related to strains isolated from tomato in Indiana, Mexico, and Louisiana. The in-planta population growth of tomato strains isolated from Indiana, Mexico, Louisiana, and Turkey in pepper leaf mesophyll was on par with pepper X. perforans and X. euvesicatoria strains. Molecular clock analysis of the 35 Florida strains dated their emergence to approximately 2017. While strains varied in copper tolerance, all sequenced strains harbored the avrHah1 transcription activation-like effector located on a conjugative plasmid, not previously reported in Florida. Our findings suggest that there is a geographically distributed lineage of X. perforans strains on tomato that have the genetic background to cause disease on pepper. Moreover, this study clarifies potential adaptive variants of X. perforans on pepper host which could help forecast the emergence of such strains and enable immediate or pre-emptive intervention.

Bacterial spot is an economically significant disease in tomato and pepper-producing countries globally. We report the whole-genome sequence of 11 Xanthomonas strains associated with bacterial spot disease on pepper, tomato and eggplant in the Southeastern Anatolia Region, Turkey. This genomic information can be used as a reference to study the genetic diversity of these species and contribute to illuminating pathogen evolution with respect to host specificity.

Bacterial spot is an economically significant disease in tomato and pepper-producing countries globally. We report the whole genome sequence of 11 Xanthomonas strains associated with bacterial spot disease on pepper, tomato, and eggplant in the Southeastern Anatolia Region, Turkey.  This genomic information can be used as a reference to study the genetic diversity of these species and contribute to illuminating pathogen evolution with respect to host specificity.

Bacterial spot is an economically significant disease in tomato and pepper-producing countries globally. We report the whole genome sequence of 11 Xanthomonas strains associated with bacterial spot disease on pepper, tomato, and eggplant in the Southeastern Anatolia Region, Turkey.  This genomic information can be used as a reference to study the genetic diversity of these species and contribute to illuminating pathogen evolution with respect to host specificity.