Abstract: Poa alpigena L. is one of the main dominant forage grasses in alpine meadow of the Gannan grassland. It plays an important role in maintaining stability and production capacity of grassland ecosystem, It is of great significance to obtain excellent rhizosphere growth-promoting bacteria resources from P. alpigena L. for the restoration of degraded grassland. The growth-promoting strains with the ability of dissolving phosphorus and fixing nitrogen were isolated and screened out from the rhizosphere of Poa alpigena L., which was collected from the Gannan grassland using a selective medium. Their growth-promoting characteristics were systematically investigated, and also their effects on seed germination and seedling growth of Poa alpigena L.. were verified. On this basis, their taxonomic status was determined using morphological identification combined with 16S rRNA gene analysis. The results showed that a total of 32 growth-promoting strains were isolated from the rhizosphere of P. alpigena L., and 5 excellent strains were screened out for further exploration. Among them, there were 4 strains for dissolving inorganic phosphorus, 3 strains for dissolving organic phosphorus and 4 strains for fixing nitrogen. All the 5 strains had the ability to secrete IAA, with the secretory quantity ranging from 9.62 to 76.16 μg·mL^-1. Additionally, they all could improve the germination rate, germination index, seedling vigor index, and promote the growth of P. alpigena L. seedlings. Taxonomic identification demonstrated 2 strains of Bacillus subtilis, 1 strain of Bacillus mycoides, 1 strain of Acinetobacter sp. and 1 strain of Pseudomonas fluorescens. This study can lay a foundation for further in-depth research on development of functional microbial resources.

Key words: Alpine grassland, Poa alpigena, Plant growth promoting rhizobacteria, Phosphate solubilizing bacteria, Nitrogen-fixing bacteria

摘要： 为获得高原早熟禾（Poa alpigena L.）根际优良促生菌资源，从甘南草原采集高原早熟禾样品，从其根际分离筛选具有溶磷、固氮能力的促生菌株，研究其促生特性，并验证其对高原早熟禾种子萌发及幼苗生长的影响，在此基础上，运用16S rRNA基因分析法确定其分类地位。结果发现：共分离出32株具有促生作用的菌株，筛选出的5株优良菌株中溶解无机磷菌株有4株，溶有机磷菌株3株，固氮菌4株；5株菌株均具有分泌吲哚-3-乙酸（Indole-3-acetic acid，IAA）的能力，分泌量在9.62~76.16 μg·mL^-1之间；待测菌均能提高高原早熟禾幼苗的发芽率、发芽指数、幼苗活力指数，并能促进高原早熟禾幼苗的生长；分类地位鉴定结果表明5株菌中有2株枯草芽孢杆菌，1株蕈状芽孢杆菌，1株不动杆菌以及1株荧光假单胞菌。本研究为进一步的促生菌机理研究和功能微生物资源开发奠定了基础。

关键词: 高寒草地, 高原早熟禾, 植物根际促生菌, 溶磷菌, 固氮菌