Abstract: Unearthing the salt-tolerant strains to develop the biological improvement agents are important ways to restore the degraded saline-alkali grassland and explore the saline-alkali wasteland be usable. DP12,DP15,DP28,DP29 were identified by morphological observation,physiological and biochemical measurements,and 16S rRNA gene sequencing analysis. The liquid mediums with different salt-alkali concentration (salt concentration was 0%,1%,3%,5%,and 7%,and the pH was 7,8,9,10,11,and 12) were used to test their saline-alkali tolerance. The functional mediums were used to measure their growth-promoting function. Meanwhile,the catalyst was quantitatively determined. The petri dish filter paper method was used to verify the effects of the strain on the germination of the seeds of Lespedeza daurica,Medicago Sativa,Triticum aestivum and Avena sativa. In order to screen out the dominant rhizosphere with growth promoting functions,the strains DP12 and DP29 were identified to be E. hormaechei,the strain DP15 was S. fonticola,the strain DP29 was S. epidermidis. All of the strains above was able to survive at the salt concentration of or less than 7%,at pH of 8~12. Through the growth-promoting function research,it was found out that all four strains had an ability to produce auxin and organic acids. Among them,the strains DP15 and DP29 had an ability to release potassium,the strains DP12,DP15 and DP29 had an ability to nitrogen fixation and produce siderophores. Strains DP12,DP15,DP29 significantly promoted the stem growth,root development and fresh weight of L. daurica,T. aestivum and A. sativa. The Strain DP28 significantly promoted the stem growth,root development and fresh weight of L. daurica and A. sative. The strains DP12 and DP28 significantly promoted the root development of M. sativa. The four strains of rhizosphere bacteria belong to moderate salt-tolerant bacteria and have multiple growth-promoting characteristics,which provide efficient and bacterial resources for the development of special biological improvement agents for L. daurica,M. Sativa, T. aestivum and A. sativa,and help to realize the potential of Enterobacter and Staphylococcus for the developments of biological improvement agents.

Key words: Loess plateau, Rhizosphere bacteria, Leguminosae, Gramineae family, Saline-alkaline tolerance, Plant growth-promoting property

摘要： 挖掘耐盐碱菌种和研发生物改良制剂是治理退化盐碱草地和开发利用盐碱荒地的重要途径。本研究通过形态学、生理生化和分子生物学手段对菌株进行鉴定，测定不同盐碱浓度下液体培养基其菌株浓度，功能性培养基测定其促生特性，定量测定其促生产物；纸培养基法验证菌株对达乌里胡枝子(Lespedeza daurica)、燕麦(Avena sativ)、紫花苜蓿(Medicago Sativa)及小黑麦(Triticum aestivum)种子生长的影响,旨在对DP12，DP15，DP28和DP29进行促生性分析。DP12，DP29初步鉴定为Enterobacter hormaechei，DP15为Serratia fonticola，可在7%盐浓度或pH12条件下生长。4株菌有溶磷、产IAA和有机酸能力；DP15，DP29有解钾能力；DP12，DP15，DP29可固氮和分泌铁载体。DP12，DP15，DP29可促进达乌里胡枝子、小黑麦和燕麦生长及鲜重的增加；DP28可促进达乌里胡枝子和燕麦生长和鲜重的增加；DP12和DP28对苜蓿具有促生作用。4株根际细菌为中度耐盐菌，兼具多重促生特性，为后期开发牧草专用生物改良制剂提供了菌种资源，有助于开发Enterobacter sp及Staphylococcus sp微生物在生物改良制剂方面的潜能。

关键词: 黄土高原, 根际细菌, 豆科, 禾本科, 耐盐碱, 促生特性