娃娃菜（Brassica campestris）软腐病病原菌的分离与鉴定

为鉴定导致娃娃菜采后软腐病的主要病原菌，以新鲜娃娃菜为试验材料，常温贮藏一定时间至发病后，选取典型软腐病病症叶片进行菌株的分离纯化和致病性测定，通过形态学观察、生理生化和分子生物学鉴定得出病原菌的相关种属。结果表明:娃娃菜软腐病病原菌株C-2和C-11菌落呈圆形，乳白色，稍凸起，菌体呈短杆状，为革兰氏阴性菌；可在37 ℃和含有7% NaCl培养基中正常生长，可利用柠檬酸盐和明胶，并能够利用葡萄糖、果糖、蔗糖、甘油、半乳糖、水杨苷、麦芽糖、甘露醇和山梨醇作为碳源发酵产酸；基于16S rDNA基因序列系统发育关系表明，C-2和C-11与其他的P.carotovorum subsp. odoriferum（Pco）菌株形成明显的Pco类群，因此，可以判断该菌株属于胡萝卜软腐果胶杆菌Pco亚种，该研究结果可以为娃娃菜软腐病的研究与防治提供理论基础。

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.