半夏细菌性软腐病原菌的分离及鉴定

Isolation and identification of a bacterial pathogen causing soft-rot on Pinellia ternata

在浙江省人工栽培的半夏[Pinellia ternata（Thunb．）Breit．]上发现一种新的软腐病害，软腐症状常常表现在块茎上，高温高湿条件可导致叶面腐烂和整株死亡。为了对病原菌进行鉴定，从软腐的半夏病株块茎中分离到10个菌株，分别指定为RF1～RF10，并进行了致病性测定、形态观察和细菌学特性分析，同时对RF1菌株进行了分子鉴定。结果表明，10个菌株均可经人工接种导致半夏、胡萝卜、马铃薯、番茄、黄瓜和白菜软腐。在电镜下菌体呈短杆状，两端钝圆，具有4～6根周生鞭毛。兼性厌氧、革兰氏阴性，DNA中G＋Cmol％为51。RF1菌株的16S rDNA测序和系统发育学分析表明，其与胡萝卜软腐果胶杆菌胡萝卜软腐亚种（Pectobacterium carotovorum subsp．carotovorum）M1菌株报告的序列相同点为99％，与该亚种另2个菌株（E161和441）的序列相同点达97％。结果表明，半夏软腐病原菌应归属于胡萝卜软腐果胶杆菌胡萝卜软腐亚种。

A new soft-rot disease was commonly found on cultivated Pinellia ternata （Thunb.） Breit. in Zhejiang province in China. Soft-rot symptom prevalently appeared on tubes, and leaves became rot or even the whole plant might die under hot and humid conditions. To investigate the causing agent of the disease, ten bacterial strains designated as RF1 - RF 10 were isolated from rotted tuber of P. ternata and characterized by etiological, morphological and bacteriological tests. Furthermore, strain RF1 was selected for analysis of 16S rDNA sequence. The results showed that all the ten isolates caused soft rot on P. ternata, as well as on carrot, potato, tomato, cucumber and Chinese cabbage in artificial inoculation tests. The bacterial cells appeared short bacillary in shape with 4 -6 peritrichous flagella under scan electronic microscope. They were facultative anaerobes and gram negative. G ＋ C mol% of the bacterial genomic DNA was measured as 51. The sequence of 16S rDNA of RFI was determined and found by BLAST shared 99% identity to that of Pectobacterium carotovorum subsp, carotovorum （Pcc）Ml strain, and 97% with those of the other 2 Pcc strains El61 and 441. It comes to the conclusion that the causing agent of soft-rot disease on P. ternata belongs to P. carotovorum subsp, carotovorum.