桑树内生菌提升三峡库区消落带桑树抗逆性能及机理的研究

The ecological security, sustainable development, people’s health, production and living conditions were threatened by the hydro-fluctuation belt and its fragile ecological environment in the Three Gorges Reservoir area. Mulberry can be used as a candidate species for vegetation restoration in damaged ecosystem. However, a series of problems, such as anti-seasonal flooding, soil erosion and poor soil quality, have heavily restricted the survival of newly planted mulberry seeding, and ultimately made it difficult to become a succession forest so as to improve the ecological environment quality. Symbiosis of plant endophytes and host plant can effectively improve stress resistance of host to harsh environment, and it is a promising strategy of ecological reconstruction. Based on the systematically study about mulberry endophytes of hydro-fluctuation belt in the Three Gorges Reservoir area, and constructed endophytes reservoir. Present research will screen out the endophytes which can enhance the resistance of mulberry, and apply them to enhance the survival rate of newly planted mulberry seedlings, and then explore the mechanisms of mulberry endophytes enhance the resistance of mulberry and promote mulberry growth. Overall, the project will provide scientific basis for application plant endophytes to promote ecological recovery of hydro-fluctuation belt of the Three Gorges Reservoir area.

三峡库区水陆交错消落带及其脆弱的生态环境，对库区生态安全、经济社会可持续发展，及两岸居民的生产、生活、健康等，构成了极大的威胁和隐患。有关消落带植被恢复物种选择的研究结果表明，桑树可作为受损生态系统植被恢复的候选物种。然而库区消落带反季节水淹、水土流失、土壤贫瘠等一系列问题，严重制约消落带成陆植桑后桑苗的存活率，最终难以成林改善消落带生态环境。通过植物内生菌与宿主植物共生，有效提高宿主植物抗病抗逆能力、促进其生长，是极具发展潜力与应用前景的生态恢复新策略。本项目在前期对库区消落带桑树内生菌开展系统研究，并构建内生菌菌种资源库的基础上，筛选能增强桑树抗逆性能的菌株，利用其帮助桑树抵抗库区不良生态环境，提高新植桑苗存活率，进而探明内生菌提高桑树抗逆性、促进桑树生长的相关机理，为利用植物内生菌促进三峡库区消落带植被恢复提供科学依据。

三峡库区消落带是因库区水位周期性调节形成的生态受损地带，桑树为消落带生态修复的潜在经济树种。消落带新植桑树存活率不高，及存活桑树长势差异显著，阻碍了利用其进行生态修复。通过植物相关功能菌促进植物生长、提高其抗病抗逆能力，是极具发展潜力的生态恢复新策略。项目组前期初步探索了库区消落带桑树内生菌群结构，并构建了桑树相关菌种资源库。本项目首先系统探究了消落带不同长势桑树相关菌群的结构特征；基于前期构建的菌种库，筛选具抗逆促生潜能的功能菌株，评估其对桑苗生长的促进作用；进一步鉴定促生效果优异的目的功能菌株，检测其对常见植物病原菌的拮抗作用及对非生物胁迫的耐受能力；并通过模拟库区干旱和水涝胁迫，系统探索目的菌株对桑树抗逆性能的影响；最终从基因组、基因功能验证及代谢物等层面，系统揭示了优质功能菌株发挥促生、抗逆作用的可能机制。库区桑树相关菌群分析结果表明，桑树相关菌群结构具有明显的组织特异性，且桑树生长状态与内生细菌群落结构紧密相关；进而检测筛选获得的12株促生功能菌株对桑苗生长的影响，结果表明Klebsiella variicola HWS1和Bacillus megaterium HGS7菌株对桑苗生长具有极为显著的促进作用，且其对部分植物病原真菌具有拮抗作用，对非生物胁迫具有较强的耐受能力。盆栽实验结果表明K. variicola HWS1菌株能显著提升桑苗对干旱及水涝胁迫的抗性。抗逆促生机制分析结果表明：HWS1基因组中存在抑菌、促生和抗逆相关的基因，功能基因验证结果表明Acd基因对HWS1菌株提升宿主抗逆性能具有关键作用，且该菌具固氮、产铁载体、ACC脱氨酶，及分泌吲哚乙酸和赤霉素等功能。本项目为利用植物相关微生物促进宿主生长、增强其抗病抗逆能力奠定了坚实基础，为后续进一步利用桑树相关菌群，提升三峡库区消落带桑树对非生物胁迫的抵抗能力提供了菌种资源及方法体系。