Characteristics and Rapid Diagnosis of Ssp. Associated With Bacterial Soft Rot of Vegetables in China

, a causal agent of vegetable soft rot, contains three valid subspecies: subsp. (), subsp. (), and subsp. (). Using 16S rDNA sequencing and genus-specific PCR, we identified 72 strains from Chinese cabbage, bok choy, and celery and assessed their pathogenicity on Chinese cabbage petioles and potato tubers. Based on phylogenetic analysis of sequences and confirmation by subspecies-specific PCR, the strains were divided into 18 , 29 , and 25 Several characteristic features were also assessed and supported the distinctiveness of the strains. All strains caused soft rot symptoms on Chinese cabbage and potato, but the strains exhibited the greatest severity. We developed a conventional PCR and a quantitative PCR (qPCR) assay for the identification of based on its specific gene encoding sorbitol-specific phosphotransferase. These two methods could specifically amplify the expected products of 674 and 108 bp, respectively, from all of the strains. The assays demonstrated high sensitivity and could detect as little as 1 and 100 pg/µl of bacterial genomic DNA, respectively. Both assays could also detect the pathogens directly from plant tissues infected with as little as 2.5 × 10 CFU/mg of , even before external symptoms appeared. These assays constitute effective tools for disease diagnosis and the rapid identification of soft rot pathogens.