广西烟草一种斑枯病新病原菌的鉴定

为明确导致广西田林县烟草叶片斑枯的病原菌种类，采用组织分离法对典型发病叶片的病原菌进行分离，并以菌丝块接种法测定分离物的致病性。用PDA和V8培养基培养并观察其形态特征，再将其rRNA-ITS和TUB2序列联合进行分子鉴定。结果表明，分离获得的代表菌株可致烟草叶片发病，在PDA培养基上不能产孢，在V8培养基上培养可形成分生孢子器和分生孢子。分生孢子器近球形，直径70 ~150 μm。分生孢子为单胞，无色，呈椭圆形，平均大小7.1 μm×2.7 μm。代表菌株的rRNA-ITS和TUB2序列Blastn比对及系统进化树分析显示，其与木瓜拟多隔孢（Stagonosporopsis caricae）的相似度分别为99.61%和100%，与S. caricae归为同一分支。结合致病性和形态特征，将广西烟草斑枯病的病原菌鉴定为S. caricae。 

Identification of a new pathogen causing tobacco spot blight in Guangxi

To identify the pathogen causing spot blight of tobacco leaves in Tianlin County, Guangxi, the pathogens were isolated from typical diseased leaves and the pathogenicity of the isolate was determined by mycelium inoculation. The isolate was cultured on PDA and V8 media and its morphological characteristics were observed, and the rRNA-ITS and TUB2 sequences of the isolate were jointly analyzed for molecular identification. The results showed that the representative isolate was pathogenic to tobacco leaves, it could not produce conidia on PDA medium, but could form pycnidia and conidia on V8 medium. The pycnidia were nearly spherical with a diameter of 70-150 μ m. The conidia were single-cell, colorless and oval in shape with the average size of 7.1 μ m × 2.7 μ m. Blastn alignment and phylogenetic tree analysis of rRNA-ITS and TUB2 sequences of the representative isolate indicated that its similarity with Stagonosporopsis caricae was 99.61% and 100% respectively, and the isolate belonged to the same branch with S. caricae. Combined with pathogenicity and morphological characteristics, the pathogen of tobacco spot blight in Guangxi was identified as S. caricae.