【摘要】 为明确广东省四季海棠叶斑病的病原菌种类，从广东省广州市番禺区采集病害样本，采用组织分离法分离病原菌，基于病菌致病性、形态和分子生物学特征确定其分类地位，获得13株形态特征相似的单孢分离物。供试菌株可侵染四季海棠，产生与田间相似的叶斑病症状。在PDA上，菌落浅灰绿色，气生菌丝丰富。分生孢子梗多单生，(36.4～102.8)μm×(4.6～8.6)μm(n=50)。分生孢子褐色，单生，倒棒形、倒梨形、卵形或椭圆形，(25.6～72.5)μm×(15.4～26.3)μm(n=50)，横隔3～7个，纵隔0～3个。基于21株链格孢属内种的ITS、TEF-1α、GAPDH、Alt a1和RPB2基因序列构建系统发育树，病原菌与番茄链格菌的4个菌株单独聚成一支。研究表明，广东四季海棠叶斑病菌为番茄链格孢(Alternaria tomato)，这是番茄链格孢侵染四季海棠的首次报道。更多还原

【Abstract】 To clarify the pathogen causing leaf spot on Begonia semperflorens in Guangdong, samples of begonia leaf spot from Panyu District, Guangzhou in Guangdong were collected as test materials. Strains were isolated by tissue isolation method. The taxonomic status of pathogens was identified based on pathogenicity determination, morphological and molecular biological characteristics. A total of 13 single-conidium-isolates with similar morphological characteristics were obtained from diseased plant samples. Artificial inoculation results showed that the tested isolates could infect Begonia semperflorens and cause typical leaf spot symptoms observed in the field. Their colonies were light gray-green with abundant aerial hyphae on PDA medium.Conidiophores were brown, solitary,(36.4-102.8) μm×(4.6-8.6) μm(n=50). Conidia were brown, obclavate,obpyriform, oval,(25.6-72.5) μm×(15.4-26.3) μm(n=50), with three to seven transverse and zero to three longitudinal septa. Based on a phylogenetic tree obtained using multiplex alignments of concatenations of ITS,TEF-1α, GAPDH, Alt a1 and RPB2 genes sequences from 21 Alternaria species, two tested isolates were grouped together with four Alternaria tomato strains to form a single clade. This study clarified that the pathogen causing begonia leaf spot in Guangdong was determined as A. tomato, which was reported for the first time that A. tomato could cause begonia leaf spot.更多还原