盐碱胁迫对紫花苜蓿根际及根内微生物群落多样性的影响

Soil salt-alkalization is a global ecological environmental problem. With the increase of soil salt content, the pH value also increased in saline-alkali soil. Saline-alkali stress reduces soil fertility, affects the whole life cycle of plants, resulting in a slowdown in growth rate of plant and a significant decrease in yield. Microorganism is an important link between plant and soil. The diversity of microorganisms in the rhizosphere and root of plant is very rich, the change of its quantity and structure has an important effect on resisting environmental stress and plant growth and development. However, little is known about the changes of rhizospheric and endophytic microbial community structure and function under saline alkali stress.. This study screens the alfalfa cultivars with tolerance or sensitive to saline-alkali stress. By using dilution plate method, Biolog analysis, high-throughput sequencing analysis and soil enzyme activity detection, to analyze the effects of saline-alkali stress on the rhizospheric and endophytic microbial community structure and functional diversity in alfalfa, and reveal the core groups of rhizospheric and endophytic microorganisms to respond to saline alkali stress, and their effects on the resistance of alfalfa to saline-alkali stress. We also isolate the endophytic bacteria from alfalfa roots, and evaluate their growth promoting effects. This study will lay the foundation for the excavation and use of alfalfa rhizospheric and endophytic microbial resources, and will provide scientific basis for improving the saline-alkali tolerance of alfalfa and the vegetation restoration and ecological reconstruction of saline-alkali soil.

土壤盐碱化是当前面临的一个世界性生态环境问题。盐碱胁迫降低土壤肥力，影响植物的整个生命周期，导致植物生长速率减慢，产量大幅下降。微生物是联系植物与土壤之间的重要纽带，植物根际及根内微生物多样性非常丰富，其数量和结构的变化对抵抗环境胁迫和植物的生长发育产生重要影响。但是，关于在盐碱胁迫下，植物根际及根内微生物群落结构和功能的变化，目前还知之甚少。. 本研究以对盐碱胁迫具有抗性和敏感的紫花苜蓿为材料，利用稀释平板法、Biolog法、高通量测序分析和土壤酶活性检测，分析盐碱胁迫对紫花苜蓿根际及根内微生物群落结构和功能多样性的影响，揭示根际及根内微生物对盐碱胁迫响应的核心类群，以及在紫花苜蓿抵抗盐碱胁迫方面的作用。从紫花苜蓿根组织分离内生菌，评价其促生作用。本研究将为挖掘利用植物根际及根内微生物资源奠定基础，为紫花苜蓿耐盐碱栽培，以及盐碱土壤的植被恢复和生态重建提供科学依据。

植物根际及根内微生物在促进植物生长和抵抗环境胁迫方面的作用已经被认识。但是，关于盐碱胁迫下，紫花苜蓿根际及根内微生物群落结构和功能多样性的变化，还缺少了解。. 本研究筛选出盐碱抗性和敏感紫花苜蓿品种。通过16S rRNA/ITS基因高通量测序和宏基因组测序，分析了盐碱胁迫对紫花苜蓿根际和根内微生物群落多样性和组成的影响。结果表明，低浓度盐碱胁迫提高了紫花苜蓿根际土壤微生物群落的多样性和丰富度，而高浓度盐碱胁迫则使之降低。低浓度和高浓度盐碱胁迫均降低了紫花苜蓿根内微生物群落的多样性。敏感种根际和根内微生物群落的多样性和丰富度均低于抗性种。与敏感种相比，抗性种在根际土壤和根内明显富集了一些包括肠杆菌属（Enterobacter）、假单胞菌属（Pseudomonas）和木霉菌属（Trichoderma）等在内具有促生能力的有益细菌和真菌分类群，且显著降低了刺盘孢属（Colletotrichum）和镰刀菌属（Fusarium）等有害真菌分类群的相对丰度。高浓度盐碱胁迫明显改变了紫花苜蓿根际土壤微生物群落的功能基因组成，降低了根际土壤中碳水化合物代谢、能量代谢、膜转运等与维持微生物正常功能和活性相关的功能基因丰度。Biolog Ecoplate分析结果表明，低浓度盐碱胁迫提高了紫花苜蓿根际土壤微生物对碳源利用的代谢活性和功能多样性，高浓度盐碱胁迫则降低了相应的功能多样性，且敏感种要低于抗性种。高浓度盐碱胁迫明显改变了紫花苜蓿根际土壤微生物对碳源的利用特征，与抗性种相比，敏感种根际微生物对羧酸、多聚物和碳水化合物等碳源的利用率明显下降。盐碱胁迫下紫花苜蓿根际土壤酶活性显著下降，且敏感种根际土壤酶活性均低于抗性种。分离筛选到8株具有ACC脱氨酶活性的耐盐碱紫花苜蓿内生菌，接种内生菌均促进了盐碱环境下紫花苜蓿的生长。. 本研究结果表明，紫花苜蓿根际和根内微生物群落多样性、组成和功能的改变，可能是抗/敏紫花苜蓿品种具有不同盐碱胁迫抗性的原因之一。本研究可为深入研究紫花苜蓿响应盐碱胁迫的机制提供重要科学依据。