Objective]In this paper,the diversity of arbuscular mycorrhizal fungi in the rhizosphere of Populus euphratica seeding in the Xinjiang Ebinur Lake National Nature Wetland Reserve was investigated by spore identification and molecular phylogeny,in order to explore AM fungi ecology function and the regulatory mechanisms to plant community structure in desert ecosystem. [Method]This study was conducted in the Xinjiang Ebinur Lake National Wetland Reserve,and the rhizosphere soil and root tissues of 7 P. euphratica seedlings were collected,respectively. The physical and chemical properties of the soil samples were determined,and the data were analyzed using SAS software. The wet sieving method was used to isolate the AM fungi spores from the rhizosphere soil of 7 P. euphratica seedlings and the spore pellet method was applied to identify the AM fungi species. Spore density and relative abundance were calculated,and AM fungi common structure and infection rate were observed. Meanwhile,the nested polymerase chain reaction was used to amplify rRNA gene fragments of AM fungi association with P. euphratica. Through sequence analysis and homology analysis,the rRNA gene fragments from AM fungi were identified and the reference sequences were obtained. Following, a phylogenetic tree was constructed with the new rRNA gene fragments and reference sequences by Mage software.[Result]The results showed that,Na +,Mg2 + and Ca2 + concentrations in the rhizosphere soils were significantly lower than in background soils,while the organic matter content of the rhizosphere soils was higher than that of the background, and the K + concentration distributed evenly. In the rhizosphere soil samples,nitrogen,phosphorus and sulfur contents were highly positively correlated with the organic matter content,while the contents of K +,Ca2 + and Na + were highly negatively correlated with the organic matter content. Eight species belonging to 3 AM fungal genera were isolated and identified in the rhizosphere soil of 7 P. euphratica. In these species,G. dominikii,G. viscosum,G. reticulatum,G. melanosporum belonged to Glomus,A. morrowae,A. excavata,A. undulata to Acaulospora,and Scu. erythropa to Scutellospora. In addition,13 new AM fungal taxa association with P. euphratica were identified and the Genbank accession number are KJ209699 - KJ209711 . After the analysis of Blast homologous alignment and phylogenetic relationship,the AM fungal taxa in P. euphratica were divided into two groups with less than 93% similarity,and the taxon of two AM fungal groups belong to different species of the genus Rhizophagus.[Conclusion]The P. euphratica with AM fungi can significantly reduce salt concentrations in the rhizosphere soil,and simultaneously increase the organic matter content,as well as the contents of nitrogen,phosphorus and sulfur. In this study,13 new AM fungal taxa association with P. euphratica were separated into two groups belonging to one genus. From this result,in the flora with P. euphratica as the constructive species,the AM fungi associated with constructive species have the host selectivity to avoid nutrition competition to each other,and hence regulate the structure of the plant community in flora.%【目的】通过对胡杨林根围土壤和背景土壤的理化因子测定及数据分析，对其根围土壤中丛枝菌根真菌( arbuscular mycorrhizal fungi，简称AM 真菌)孢子分离与鉴定以及对其根系共生AM 真菌进行群落构成进行分子鉴定，分析荒漠生态系统中胡杨幼苗AM 真菌共生状况和群落结构特点，以探讨荒漠生态系统中胡杨根际共生AM 真菌生态学功能及其对地上植物群落结构的影响。【方法】在新疆艾比湖国家自然湿地保护区，分别采集胡杨保护林中7株胡杨幼苗根围土壤及根组织。对土样理化因子进行测试并采用 SAS 软件对数据进行统计分析。采用湿筛法对胡杨根围土壤中 AM 真菌孢子进行分离，压片法进行孢子鉴定，并计算 AM 真菌孢子密度和不同 AM 真菌孢子的相对多度，同时检测胡杨根系 AM 真菌侵染率及侵染结构。最后采用巢式 PCR 的方法扩增胡杨根系共生 AM真菌核糖体 RNA基因序列，并对序列进行测序分析，再进行Blast比对获得胡杨根系共生AM 真菌的种属关系和标准序列，采用 Mage软件构建系统发育树。【结果】胡杨根围土壤中 Na +，Mg2+和 Ca2+浓度显著的低于背景土壤，有机质含量高于背景土，而 K +分布均匀；根围土壤中的氮、磷和硫含量与有机质含量为高度正相关，而钾、钙和钠的含量与有机质含量为负相关。孢子鉴定共从7株胡杨幼苗根围土中分离鉴定出 AM 真菌3属8种，分别为球囊霉属的道氏球囊霉、粘质球囊霉、网状球囊菌、黑球囊霉；无梗囊霉属的毛氏无梗囊霉、凹坑无梗囊霉、波状无梗囊霉；巨孢囊霉属的红色盾巨孢囊霉。此外对与胡杨幼苗共生的 AM 真菌进行分子鉴定，共检测出13个新的 AM 真菌分类单元，Genbank登录号为： KJ209699－KJ209711。聚类分析结果显示，从胡杨根际鉴定的 AM 真菌分为2个相似性小于93%的类群，2个类群 AM 真菌属于 Rhizophagus 属中不同的种。【结论】与 AM 真菌共生的胡杨幼苗可显著的降低其根围土壤中的盐离子浓度，同时可提高有机质的含量，并对氮、磷和硫营养元素具有富集效应。本试验分子鉴定法获得13个 AM 真菌新的分类单元比对后属于 Rhizophagus 属2个不同的种，由此可知在艾比湖流域内以胡杨为建群种的植物区系内，其根系 AM 真菌种类单一，有助于减少胡杨个体彼此之间的营养竞争作用，从而增强胡杨群体在群落内的竞争能力，并最终影响地上植物群落的结构。
展开▼
