Development and validation of real‐time PCR tests for specific identification of Xanthomonas species causing bacterial spot disease on tomato (Solanum lycopersicum) and pepper (Capsicum annuum)

Abstract

AbstractBacterial spot is a significant disease of tomato and pepper crops caused by members of four Xanthomonas pathogens from three species, namely Xanthomonas euvesicatoria pv. euvesicatoria, Xanthomonas euvesicatoria pv. perforans, Xanthomonas vesicatoria and Xanthomonas hortorum pv. gardneri. These Gram‐negative bacterial plant pathogens are recommended for regulation as quarantine pests by the European and Mediterranean Plant Protection Organization and are currently regulated on tomato and pepper seeds in many regions of the world. Tomato and pepper seeds are a transmission pathway for all three species. Real‐time PCR TaqMan tests were developed and validated for specific identification of isolates from tomato and pepper seeds of these pathogens. These tests are designed to be used in seed health tests after isolation on semiselective media to reduce the number of isolates that need testing in follow‐up pathogenicity tests. A second set of real‐time TaqMan PCR tests was subsequently developed targeting two markers for each taxonomic group of strains. The analytical specificity of all developed tests was evaluated with in vitro and in silico analyses. Diagnostic specificity and sensitivity were also validated on collections of isolates in several laboratories.