水稻胡麻叶斑病病原菌的分离及鉴定

【目的】对水稻胡麻叶斑病病原菌进行分离和鉴定，为进一步研究该病的发病机理和有效防控奠定基础。【方法】采用常规真菌分离方法分离水稻胡麻叶斑病病原菌，通过回接试验进行柯赫氏法则验证，对确认为水稻胡麻叶斑病病原菌的菌落进行形态学和分子鉴定。【结果】经回接试验确认分离的水稻胡麻叶斑病病原菌的分生孢子梗单生，褐色，不分枝，顶端呈膝状弯曲，分生孢子呈长椭圆形、梭形、倒棍棒状，正直或向一侧弯曲，褐色，两端渐狭，钝圆，种脐较平，有5～10个假隔膜。18S rDNA和ITS序列长度分别约为1.8 kb和570 bp,与待鉴定病原菌18S rDNA同源性最高的是狗牙根平脐蠕孢有性态（Cochliobolus cynodontis），二者的相似度为99%；与其ITS序列同源性最高的是稻平脐蠕孢（Bipolaris oryzae），二者的相似度也为99%。聚类分析发现，该病原菌与蟋蟀草平脐蠕孢（Bipolaris eleusines）的18S rDNA同源关系最近，与平脐蠕孢属（Bipolaris sp.）的ITS同源关系最近。【结论】成功分离到水稻胡麻叶斑病病原菌，形态学与分子鉴定结果均显示其为稻平脐蠕孢。

Isolation and identification of pathogenic fungi of rice brown spot

【Objective】 The isolation and identification of pathogenic fungi of rice brown spot were studied,which laid the foundation for further study of the pathogenesis of the disease and effective prevention and control.【Method】 The pathogenic fungi of rice brown spot was separated by using the conventional separation method of the fungal.The inoculation experiment was verified by Koch’s postulates.The pathogen colonies of rice brown spot were identified by the morphological and molecular.【Result】 The separation of the pathogenic fungi of rice brown spot was confirmed by inoculation experiment.Its conidiophores of the pathogenic fungi of rice brown spot isolated were single,brown,not branched and their tops were geniculation.Conidia was elongated oval,spindle,pour sticks shape,straight or bent to one side,brown,the both ends of the conidia gradually narrowed,obtuse,its hilum was relatively flat,5-10 replums;The lengths of 18S rDNA and ITS sequence were respectively about 1.8 kb and 570 bp.Homdogy between the 18S rDNA of pathogen identified and one of Cochliobolus cynodontis was the highest,and their similarity was 99%;homology between the ITS of pathogen identified and one of Bipolaris oryzae was the highest,and their similarity was 99%.Cluster analysis indicated that this pathogen had the closest relation with the 18S rDNA of Bipolaris eleusines and the ITS of Bipolaris sp.【Conclusion】 The pathogenic fungus of rice brown spot was successfully isolated from the rice;The results of morphological and molecular identification were both B.oryzae.