Pseudomonas capsici sp. nov., a plant-pathogenic bacterium isolated from pepper leaf in Georgia, USA

Three phytopathogenic bacterial strains (Pc19-1(T), Pc19-2 and Pc19-3) were isolated from seedlings displaying water-soaked, dark brown-to-black, necrotic lesions on pepper (Capsicum annuum) leaves in Georgia, USA. Upon isolation on King’s medium B, light cream-coloured colonies were observed and a diffusible fluorescent pigment was visible under ultraviolet light. Analysis of their 16S rRNA gene sequences showed that they belonged to the genus Pseudomonas , with the highest similarity to Pseudomonas cichorii ATCC 10857(T) (99.7 %). The fatty acid analysis revealed that the majority of the fatty acids were summed feature 3 (C(16 : 1) ω7c/C(16 : 1) ω6c), C(16 : 0) and summed feature 8 (C(18 : 1) ω7c/C(18 : 1) ω6c). Phylogenomic analyses based on whole genome sequences demonstrated that the pepper strains belonged to the Pseudomonas syringae complex with P. cichorii as their closest neighbour, and formed a separate monophyletic clade from other species. Between the pepper strains and P. cichorii , the average nucleotide identity values were 91.3 %. Furthermore, the digital DNA–DNA hybridization values of the pepper strains when compared to their closest relatives, including P. cichorii , were 45.2 % or less. In addition, biochemical and physiological features were examined in this study and the results indicate that the pepper strains represent a novel Pseudomonas species. Therefore, we propose a new species Pseudomonas capsici sp. nov., with Pc19-1(T) (=CFBP 8884(T)=LMG 32209(T)) as the type strain. The DNA G+C content of the strain Pc19-1(T) is 58.4 mol%.