中文摘要：

[目的]本文旨在确定圆柱披碱草（Elymus cylindricus）内生真菌的分类地位。[方法]选择5株分离自新疆、青海的圆柱披碱草内生真菌菌株,采用SDS法提取基因组DNA,利用选择性引物对其tub B和tef A基因片段进行扩增和克隆测序,下载NCBI中的相似序列并进行比对分析,用MEGA 6.0软件构建系统发育树。[结果]成功获得差异极小的各菌株序列,且tub B序列确认为仅1个拷贝,而2个菌株的tef A序列则有2个拷贝。在最大简约树上披碱草菌株的tef A和tub B第1拷贝均在EBY（Epichloe bromicola/E.yangzii）大支上,与E.sinica比较接近;tef A的第2拷贝与ETC（E.typhina complex）中的成员聚类。[结论]Epichloesp.-Elymus cylindricus是一个新的共生体组合。圆柱披碱草分离菌株为杂交起源的Epichloe属真菌,可能起源于E.bromicola（syn.E.yangzii）和E.sylvatica间的杂交。

英文摘要：

[Objectives]To identify the endophyic strains obtained from Elymus cylindricus,phylogenetic analysis were conducted.[Methods]Five fungal strains were incubated. Then their genomic DNA samples were extracted by SDS extraction method. Fragments of β-tubulin（ tub B） and translation elongation factor 1-α（ tef A） genes were amplified by specific PCR primers for isolated strains.Related sequences of tub B and tef A were downloaded from NCBI,then were aligned and analyzed by DNAssist and Bio Edit. The phylogenetic characteristics of these strains were analyzed through the Maximum Parsimony tree performed by MEGA 6.0. [Results]All the sequence were nearly similar. Five strains were confirmed to possess single alleles of tub B,while 2 of them had 2 alleles of tef A.In the tree based on tub B fragment,they clustered together with Epichloe sinica within EBY（ Epichloe bromicola / E. yangzii） clade. In the tree based on tef A fragment,allele-1 were grouped with E. sinica,while allele-2 within the ETC（ E. typhina complex） clade.[Conclusions]They might be a new association of hybrid Epichloe sp.-Elymus cylindricus symbiosis. Strains obtained from Elymus cylindricus could origin from hybridization of E. bromicola（ syn. E. yangzii） and E. sylvatica.