Isolation and Identification of Pathogenic Bacteria Causing Soft Rot of Brassica campestris

In order to identify the main pathogenic bacteria causing soft rot after harvest, some fresh Brassica campestris were chosen as the experimental material and stored at room temperature for a certain time until the onset of disease. The typical leaves of soft rot disease were selected for isolation, purification and determination of pathogenicity. Related species and genera of pathogenic bacteria were obtained through morphological observation, physiological and biochemical identification and molecular biology identification. The results showed that the bacterial colonies of C-2 and C-11 were round, milky, slightly raised, and the bacteria were short rod-shaped, which were Gram-negative bacteria. It could grow normally at 37 ℃ and in medium containing 7% NaCl. Citrate and gelatin could be used, and glucose, fructose, sucrose, glycerin, galactose, salicin, maltose, mannitol and sorbitol could be used as carbon source fermentation to produce acid. Based on the phylogenetic relationship of 16S rDNA gene sequence, C-2 and C-11 formed obvious P.carotovorum subsp. odoriferum (Pco) group with other Pco strains. Therefore, it could be concluded that the strain belonged to the species of Pectobacterium carotovorum (Pc), the subspecies of Pco. The results of this study could provide reference for the research and prevention of soft rot of Brassica campestris.