甘薯茎腐病症状及其病原鉴定

Characterization of stem and root rot symptoms of sweet potato and the causal pathogen of the disease

甘薯茎腐病是危害甘薯的一种严重病害,甘薯茎、叶柄、叶片和块根均可被害。该病典型症状是茎基部发黑和变软腐烂,叶发黄,茎和块根维管束黑褐色,引起块根腐烂、有臭味。通过对甘薯茎腐病典型症状样本的采集、病原菌的分离和纯化以及致病性测定,明确该病害是一种细菌病害。通过对甘薯茎腐病菌的菌体形态和培养特性观察发现,病原菌是革兰氏阴性细菌,菌体短杆状,大小约为2.36μm×0.4μm,周生鞭毛,可在烟草上激发过敏性反应(HR)。Biolog测定、脂肪酸分析、16S rDNA序列分析、MALDI-TOF质谱鉴定和8个看家基因(dnaX、rplB、fusA、gapA、gyrA、purA、recA和rpoS)的序列系统发育分析,发现该病原菌与达旦提狄克氏菌Dickeya dadantii高度一致。这些结果说明,浙江省发生的小番薯病害是甘薯茎腐病,病原为D.dadantii。

Bacterial stem and root rot of sweet potato is a severe disease which can infect its stems,petioles,leaves and tuberous roots. The typical symptoms of the disease include black and rot basal stems,yellow leaves,dark brown vascular stems and smelly tuberous roots. On the basis of typical symptoms,pathogen isolation,purification and pathogenicity test,it was confirmed that it was a bacterial disease. Through the observation of the bacterial morphological and cultural characteristics,it was found that the pathogen is a short rod-shaped,gram-negative bacterium with peritrichous flagella,2.36 μm × 0.4 μm in size,and can elicit the hypersensitive response（ HR） in tobacco. According to Biolog test,analysis of fatty acid methyl esters and 16 S rDNA sequence,MALDI-TOF mass spectrometry test and phylogenetic sequence analysis of 8 house-keeping genes,dnaX,rplB,fusA,gapA,gyrA,purA,recA and rpoS,it was found that the pathogen shares high similarity with Dickeya dadantii. These results indicated that the stem rot disease of sweet potato in Zhejiang Province was caused by D. dadantii.