芝麻白绢病病原菌的分离鉴定及其生物学特性

Identification and characterization of sesame southern blight pathogen

为了明确芝麻白绢病的病原菌,采用常规组织分离法分离病原菌,依据柯赫法则、形态特征及核糖体基因内转录间隔区(rDNA-ITS)序列进行鉴定,同时检测其部分生物学特性。结果表明:引起芝麻白绢病的病原菌为罗氏阿太菌Athelia rolfsii(无性世代:齐整小核菌Sclerotium rolfsii);该菌适宜生长温度为22～34℃,最适生长温度为31℃;在pH4.0～9.0范围内均可生长,以pH 6.5～7.0生长最好,表明微酸性至中性环境最有利于菌体生长;该菌虽能利用供试的13种碳源和8种氮源进行营养生长,但在以可溶性淀粉、蔗糖、葡萄糖、麦芽糖、L-阿拉伯糖和菊糖分别作为唯一碳源并配以硝酸盐为氮源的生长条件下不产生菌核,而在以葡萄糖为碳源并配以铵盐为氮源的生长条件下可产生菌核。与合成培养基相比,A.rolfsii在天然培养基上生长更好,可形成更多、更大的菌核。

To identify and characterize the pathogen causing sesame southern blight, the pathogen was isolated and its pathogenicity to sesame plants was confirmed based on Koch＇s postulates. Pathogen identification was carried out based on morphological characteristics and ribosomal DNA internal transcribed spacer （rDNA-ITS ） sequences. Partial biological characteristics of the pathogen were tested in vitro. The pathogen causing sesame southem blight was identified as Athelia rolfsii （anamorph：Sclerotium rolfsii）. The temperatures suitable for its growth were 22 to 34℃ with the optimum temperature at 31℃. A. rolfsii grew well at a pH range of 4.0 to 9.0 with the optimum pH at 6.5 to 7.0, indicating that slight acidic to neutral environment was more suitable for vegetative growth of the pathogen. The pathogen could utilize all of the 13 tested carbon sources for its vegetative growth. However, no selerotia were developed on the media containing each of the seven substances （soluble starch, saeeharose, glucose, maltose, D-fructose, L-arabinose and inulin） as a carbon source and nitrate as the nitrogen source. A. rolfsii could produce sclerotia on the media containing glucose as a carbon source and ammonium salt as the nitrogen source. More A. rolfsii selerotia with larger size developed on natural media than on synthetic media.