云贵高原天然豆科牧草根瘤菌区系分析与利用及环境因子对共生结瘤的效应机制研究

The symbiotic nitrogen fixation between legume and rhizobia is the strongest system in the biological nitrogen fixation system,which dominates the nitrogen cycle of the earth and plays a major role in improving soil quality, impacting vegetation succession and ecological restoration. On the Yunnan-Guizhou plateau, the karst topography is remarkable, where the ecological environment is worsening, the economy is poor, and it has profound significance to develop green agriculture based on the regional characteristics and by using the symbiotic nitrogen fixation resources. Ecogeographical environment has an important impact over the diversity of legume rhizobia, and this project is designed to investigate the abundant resources of natural legume herbage rhizobia in Yun-Gui plateau where the geographic environment is special, to analyze the rhizobial flora through separation, purification and identification of rhizobia strains, and to establish a resource library of superior rhizobial strains by means of screening approach. Furthermore, in this project the effect of environment factors on the symbiotic nodulation efficiency of legume and rhizobia is to be studied systematically by carrier culture technique and potted planting methods, and the effect mechanism is to be parsed. Thus, this project could increase the understanding of the diversity and specificity of the symbiotic resources of natural legume herbage rhizobia in Yun-Gui plateau, lay a reliable material foundation for the developing of high efficient compound inoculation agents and expanding and applying in the production, provide a theoretical underpinning and technical support for the remediation of ecological environment and promotion of sustainable development of regional agriculture and grassland ecological animal husbandry.

豆科植物-根瘤菌共生固氮是生物固氮体系中最强的共生系统，主导着地球的氮素循环，在改善土壤质量、影响植被演替以及生态修复中起着极其重要的作用。云贵高原喀斯特地形显著，生态恶化，经济贫困，立足区域特点，利用共生固氮资源发展绿色农业，意义深远。生态地理环境对豆科植物根瘤菌多样性有着重要影响，本项目针对云贵高原特殊的地理环境，拟对丰富的天然豆科牧草根瘤菌资源展开系统调查，通过菌株的分离、纯化、鉴定，进行区系分析；通过高效共生固氮菌株的筛选，建立云贵高原天然豆科牧草优良根瘤菌株资源库；同时采用盆栽和载体培养的方法，系统研究环境因子对豆科植物-根瘤菌共生结瘤效率的作用关系，解析其效应机制，进而在增加对本地区天然豆科牧草及其根瘤菌共生资源多样性与特异性认识的同时，为研制高效复合接种剂并在生产中推广应用奠定可靠的物质基础，为修复生态环境并促进地区农业及草地生态畜牧业的可持续发展提供理论基础和技术支持。

受地形、气候、土壤结构等综合因素的影响，云贵高原生长着种类繁多的天然豆科牧草，并蕴藏着大量抗寒耐瘠、固氮效率高的根瘤菌，具有丰富的根瘤菌自然资源。本项目针对云贵高原特殊的地理环境，对贵州全境、云南东部和广西西北部不同生态环境中天然豆科牧草的根瘤资源进行了调查，调查样地823处，采集到白三叶、天蓝苜蓿、葛藤、多花木蓝等共26种天然豆科牧草的根瘤样品525份，研究了云贵高原天然豆科牧草共生结瘤特性与牧草种类及生态条件的关系；从根瘤中分离得到1872个纯化菌株，采用分子生物学方法，鉴定出其中1023株属于根瘤菌，另外849株属于根瘤内生细菌。鉴定分类显示，1023个菌株分属于12个属99个种，区系分析对每一个属每一个种在调查范围内的分布频率与优势地位作出了明确界定。通过盆栽回接实验，根据结瘤促生效率与固氮活力，已筛选出133个高效结瘤固氮根瘤菌株，建立了优良根瘤菌株资源库。采用盆栽和载体培养的方法，系统研究了土壤类型、环境pH、氮肥及其它矿质元素、温度与光照、盐浓度、重金属及抗生素等环境因子对根瘤菌与宿主作物结瘤固氮效率的作用关系，解析了各环境因子对共生结瘤的影响特征。项目取得的研究结果，在增加对本地区天然豆科牧草及其根瘤菌共生资源多样性与特异性认识的同时，能为制备高效复合接种剂并在生产中推广应用奠定可靠的物质基础，为修复生态环境并促进地区农业及草地生态畜牧业的可持续发展提供理论基础和技术支持。