云南烟草赤星病菌及近似种rDNA ITS序列分析

 为了进一步研究云南省烟草赤星病病原的系统发育关系，提取28份供试菌株的菌丝基因组DNA，进行rDNA ITS序列及两侧ITS序列扩增。28个供试菌株与GenBank中登录的链格孢属7个种（包括5个小孢子种Alternaria citri，A．alternata，A．longipes，A．mali，A．gaisen和2个大孢子种A．porri，A．solani）14个菌株的序列进行聚类分析：42个菌株明显地分成两支，供试菌株与5个小孢子种聚为一个分支，序列同源性高达99％～100％，没有明显的地域性差异；但另2个大孢子种聚为单独的一支，明显地与供试菌株和其他5个小孢子种区分开。rDNA ITSl 58S ITS2序列在相对保守的基础上又存在一定变异，在一些菌物属的研究中可作为分类鉴定、分子标记、系统发育的重要依据，但通过对世界各地Alternaria菌株序列的分析发现，rDNA ITS1 58S ITS2仅能将大孢子种和小孢子种分开，还不能作为区分不同地域不同来源菌株的标准。

rDNA ITS Sequence Analysis of Alternaria alternata in Yunnan and their Similar Species

To further study the phylogeny relations of Alternaria alternata, the mycelial genomic DNA were extracted to amplify the rDNA ITS sequences, and both sides of the ITS amplification. The results showed that: the sequence homology of the 28 tested strains and 5 smaller spore species including Alternaria citri, A. alternata, A. longipes, A. mali, A. gaisen by registered with the GenBank, was up to 99％～100％, which had high homology and there was no obvious regional characteristics, however, other two larger spore types A．porri and A. solani were together for another cluster, which can be clearly and distinguished from other 5 small spores species and the 28 tested strains. rDNA ITSl 58S ITS2 sequences exist a certain variation on the basis of a relatively conservative, which can be used as identification, molecular markers, an important basis for phylogeny in some genera of fungi, but it was shown that rDNA ITS1 58S ITS2 could only separate the megaspore and microspore species, and not distinguish from the Alternaria strains collected from different sources around the world.