黄瓜霜霉病和白粉病病原菌的rDNA-ITS序列分析

为了应用分子特征确定黄瓜霜霉病和白粉病的病原菌种类,扩增、测定了上海地区黄瓜霜霉病菌和白粉病菌的核糖体DNA内转录间隔区(rDNA-ITS)序列,依据rDNA-ITS序列特征分析了两种病原菌种类,以及与近缘种的差异性。结果显示,黄瓜霜霉病菌的rDNA-ITS1和rDNA-ITS2长度分别为141和406 bp,rDNA-ITS1 GC含量为41.13%,rDNA-ITS2 GC含量为46.80%(闵行区株和金山区株)或46.55%(浦东新区株),rDNA-ITS序列在种内保守性很高,种间差异性与亲缘关系呈正相关,分子特征证实研究的黄瓜霜霉病病原菌为古巴拟霜霉菌;黄瓜白粉病菌的rDNA-ITS1和rDNA-ITS2长度分别为136和89 bp,GC含量分别为59.56%和66.29%,rDNA-ITS序列在研究材料中保守,与瓜类单囊壳(Sphaerotheca cucurbitae)完全相同,但与形态鉴别的结果Sphaerotheca fuliginea差异高达4.5%,提示黄瓜白粉病病原菌的种类需进一步澄清和确定。

rDNA-ITS sequence analysis of cucumber downy mildew and cucumber powdery mildew's pathogen

To determine the pathogenic species of cucumber downy mildew and cucumber powdery mildew by molecular marker,rDNA-ITS region of the cucumber downy mildew and cucumber powdery mildew's pathogen from Shanghai was amplified and sequenced.The intra-/interspecific sequence difference was analyzed by rDNA-ITS sequence.The results showed that the lengths of rDNAITS2 and rDNA-ITS2 were 141 bp and 406 bp,and their GC contents were 41.13% and 46.80%(sm1/sm2)/46.55%(sm3) with cucumber downy mildew's pathogen,respectively.The rDNA-ITS sequence was highle intraspecific conservative,and interspecific difference was related with their kin relationship.Pseudoperonospora cubensis was identified as pathogen of cucumber downy mildew by molecular marker.The length of rDNA-ITS1 and rDNA-ITS2 were 136 bp and 89 bp,and GC contents were 59.56% and 66.29% with cucumber powdery mildew's pathogen,respectively.rDNA-ITS sequence was conservative in this study,and was the same as Sphaerotheca cucurbitae.But the sequence difference between the strains of Shanghai in this study and S.fuliginea was 4.5%,which was identified by morphology.It was suggested that the pathogenic species of cucumber powdery mildew should be clarified and determined in future.