Exploring Diversity of Bacterial Spot Associated Xanthomonas Population of Pepper in Southwest Florida

Abstract

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

Draft genome sequences of 11 Xanthomonas strains associated with bacterial spot disease in Turkey

“… X. perforans , formerly known as bacterial spot pathogen on tomato only, has recently been shown to have expanded its host range to pepper as an emerging pathogen [2, 3, 9, 10]. We found X.…”

“…However, in the last decade, a host range shift in the X. perforans population to include pepper as a host has been observed in North America [2, 3, 9, 10]. Surveys of Xanthomonas populations in other growing regions are needed to identify host-range shifts.…”

Draft genomes announcement of Vietnamese Xanthomonas euvesicatoria strains causing bacterial spot on pepper

“…Pathogenicity and pepper race determinations in pepper differentials were determined as explained in Subedi et al . [ 4 ]. Briefly, the pepper cultivar 'Early California Wonder' (ECW) and its near-isogenic lines carrying resistance genes ( Bs1 , Bs2 , Bs3 ) were infiltrated with bacterial suspensions of 10 8 c.f.u.…”

Diversification of an emerging bacterial plant pathogen; insights from the global spread ofXanthomonas euvesicatoriapv.perforans

“…Effector content varies among Xanthomonas species and distinct lineages of X. perforans have distinguishable effector content 8,31,33,40,41 . Early populations of X. perforans were limited to tomato 42 , but now it has been found to cause bacterial spot disease of pepper 33,41,43 . Host range expansion was attributed, in part, to loss of effectors that act as avirulence factors in pepper and other genomic changes as a result of recombination with other Xanthomonas lineages, including pepper pathogenic X. euvesicatoria .…”

“…were limited to tomato 42 , but now it has been found to cause bacterial spot disease of pepper 33,41,43 . Host range expansion was attributed, in part, to loss of effectors that act as avirulence factors in pepper and other genomic changes as a result of recombination with other Xanthomonas lineages, including pepper pathogenic X. euvesicatoria.…”