烟草叶斑病病原菌的鉴定及其生物学特性

Identification and characterization of the pathogen Didymella segeticola causing tobacco leaf spot

为明确贵州省新发现的烟草叶斑病病原菌种类和生物学特性,2019年自田间采集具有典型发病症状的烟叶,采用组织分离法对其进行分离纯化,对分离菌株进行致病性测定,观察病原菌形态学特征,基于ITS、LSU、tub2和rpb2基因序列进行分子生物学鉴定,同时对病原菌的生物学特性进行测定。结果显示,烟草叶斑病病斑呈圆形或椭圆形,病斑中间呈浅褐色,边缘呈棕色,周围环绕黄色晕圈。经分离纯化共获得3株病原菌,形成的菌落为深褐色,气生菌丝呈白色;分子孢子器呈球形或扁球形,为深褐色,大小为79.3~91.7μm×148.4~167.3μm;分生孢子呈椭圆形,光滑,无隔膜,具0~3个油球,大小为3.5~5.6μm×1.7~2.9μm。根据形态学特征和分子生物学特征将其鉴定为Didymella segeticola。该病原菌菌丝生长适宜温度为20~25℃;适宜pH为6~10,最适碳源为乳糖,最适氮源为蛋白胨,通气和光暗交替环境有利于其生长。

To clarify the newly discovered pathogen causing tobacco leaf spot in Guizhou Province and its biological characteristics,the tobacco leaves with typical disease symptoms were collected from the field for pathogen isolation,purification and pathogenicity determination.The morphological character-istics of pathogen was observed,and its ITS,LSU,tub2 and rpb2 gene sequences were analyzed,the biological characteristics of the pathogen was also determined.The results showed that the tobacco leaf spot was round or oval,light brown in the center and brown at the edge,surrounded by a yellow halo.Three pathogenic strains were obtained by isolation and purification.Their colonies were dark brown with white aerial mycelium,and their pycnidia were spherical or flattened,dark brown,and 79.3-91.7µm×148.4-167.3µm in size with conidia oval,smooth,without septum,with 0-3 oil globules,3.5-5.6µm×1.7-2.9µm.Combining the results of morphological characteristics and phylogenetic analysis,the pathogen was identified as Didymella segeticola.The optimum temperature range for growth of the strains of D.segeticola was 20-25℃,the optimum pH range was 6-10,the optimum carbon and nitro-gen sources were lactose and peptone,respectively,and the ventilated environments with alternating light and dark were conducive to its growth.