广东甘薯疮痂病病原菌鉴定

Identification of pathogen causing sweet potato scab in Guangdong

【目的】明确广东甘薯疮痂病的病原菌种类及生物学和系统发育学特征,为甘薯疮痂病防治及抗病育种提供参考。【方法】从广东省茂名和湛江等甘薯产区采集甘薯疮痂病植株,采用分生孢子悬液梯度稀释分离法分离病原菌,通过病原菌的形态特征观察、致病力测定,结合核糖体内转录间隔区(ITS)、28S核糖体RNA(LSU)、RNA聚合酶II第二大亚基(rpb2)和翻译延伸因子1-α(TEF1)部分序列的多核苷酸序列系统学分析等方法对病原菌进行鉴定。【结果】共分离获得26株单分生孢子分离物,随机选取3株代表性菌株SPEb-1、SPEb-2和SPEb-3进行观察和测定。光学显微镜下观察发现,3株代表性菌株的产孢细胞透明,内生芽殖;分生孢子单细胞,透明,短棒形,两侧顶端钝圆,大小为6.1~9.0μm×2.2~3.0μm;分生孢子梗短棒状;致病性人工接种表明,3株代表性菌株均可侵染甘薯引起典型的疮痂病症状。3株代表菌株的ITS、LSU、rpb2和TEF1序列与痂囊腔菌属(Elsino?)的E.ampelina、E.bidentis、E.arachidis、E.mimosae、E.ricini和E.sesseae等多个种的对应序列一致性为95%~99%。系统发育进化树分析结果显示,3株代表性菌株与蓖麻痂囊腔菌(E.ricini)单独聚成一支。【结论】广东甘薯疮痂病的病原菌为甘薯痂囊腔菌(E.batatas)。

【Objective】To clarify the species,biological and multigene phylogenetic characteristics of the pathogen of sweet potato scab in Guangdong,and provide a theoretical basis for disease control of sweet potato scab and disease resistant variety breeding.【Method】Samples that showed scab symptoms of sweet potato plants were collected in Maoming and Zhanjiang of Guangdong.The conidial suspension serial dilution method was used to isolate the pathogen.The pathogen was identified by morphological characterization and phylogenetic analysis using partial sequences of the internal transcribed spacer(ITS)regions,28S ribosome RNA(LSU),RNA polymerase II second largest subunit(rpb2)and translation elongation factor EF-1α(TEF1).Pathogenicity of the pathogen to sweet potato plants was also tested.【Result】Twenty-six single-conidium-isolates with similar colony characteristics of sweet potato scab were obtained.Three representative isolates,including SPEb-1,SPEb-2 and SPEb-3,were randomly selected for morphological observation and pathogen identification.Morphological observation results of three representative isolates using light microscope showed that conidiogenous cells were hyaline,endophytic.Conidia were single celled,hyaline,short rod-shaped,with obtuse apex,with the size of 6.1-9.0μm×2.2-3.0μm.Conidiophores were subcylindrical.Artificial in vivo inoculation results showed that these three representative isolates could infect sweet potato and cause typical scab symptoms.Phylogenetic analysis results using multiple gene loci showed that identities of sequences of ITS,LSU,rpb2 and TEF1 genes of three representative isolates were 95%to 99%identical to those of E.ampelina,E.bidentis,E.arachidis,E.mimosa,E.ricini and E.sesseae.The phylogenetic tree showed that three representative isolates were grouped together with E.ricini to form a single clade.【Conclusion】This study clarifies that the pathogen causing sweet potato scab disease in Guangdong is E.batatas.