β-葡聚糖影响土壤微生态的作用机制研究

The variation of soil microbial ecology and the propagation of soil-borne fungi (SBF) aroused by the plant monocropping are the important factors for the continuous cropping obstacles. The effective control of plant diseases caused by SBF is a worldwide problem, which constrains the sustainable development of the agricultural production. This project is based on our previous study that the addition of the β-glucan with specific structure and properties in low dose gives rise to the significant change of soil microbial ecology and lowers the quantity of SBF communities, which might be a potentially novel cure for the control of SBF. In this project we will systematically study the effects of a series of factors of β-glucan, including the structure, degree of polymerization, and dose-dependence, on the soil microbial ecology using molecular ecological techniques, and emphasize on the analysis of the dynamics of SBF communities. Thereafter, we will study the dynamics of the degradation of β-glucan in soil to facilitate the exploration of the suppression efficacy and mechanisms of β-glucan on SBF-caused plant diseases by means of the molecular biological methods and the interrelationship among the microbial communities in soil. At last, we will evaluate at the transcriptome and metabonome levels the defense responses of plant roots elicited by the β-glucan and the related β-glucooligosaccharides. This project will provide the new insight on the biocontrol of soil-borne fungi.

作物连作诱发的土壤微生态变化以及土传病原真菌种群的增殖是造成连作障碍的重要原因。土传病原真菌病害的高效防治已经成为一个世界性难题，严重制约着农业生产的可持续发展。我们前期研究结果表明，外源添加微量的特殊结构和性质的β-葡聚糖引起土壤微生态效应的显著变化，导致土传病原真菌种群数量减少。本项目拟利用分子生态的手段系统地研究外源β-葡聚糖分子结构、聚合度以及使用量等系列因素对土壤微生态效应的影响，重点关注土传病原真菌种群的动态变化；然后，结合外源β-葡聚糖在土壤中的降解特性及动力学特征，利用分子生物学技术结合土壤微生态系统中微生物种群间相互作用关系，研究外源β-葡聚糖对典型土传病原真菌导致的作物感染的防治效果及其规律；最后，从基因转录和表达水平分析β-葡聚糖及其降解产物β-葡寡糖诱导的植物根系对土传病原真菌的抗性效应以及机制。研究结果将为土传病原真菌的生态防治提供新的理论依据。

土壤微生物区系变化导致的土传病原真菌爆发性增殖是造成作物连作障碍的重要原因。土传病害严重制约着农业生产的可持续发展。本项目研究了一种水溶性β-葡聚糖（索拉胶）作为诱导剂调节土壤微生物区系结构变化的机制。研究发现，索拉胶（1）诱导提高了土壤中部分抗病酶系的活力并对土壤理化性质产生了积极影响，促进了微生物生物量碳积累；（2）改变了土壤微生物群落结构和多样性分布；（3）通过促进植物益生菌竞争性生长和拮抗等作用减少根际土壤中病原真菌含量，降低植物发病率；同时，（4）其水解产物（β-葡寡糖）作为激发子激活了植物防御响应，提高了植物对病原菌的抗性。结果表明，土壤中添加0.02% (g/g绝干土)索拉胶60天后，典型病原菌尖孢镰刀菌的丰度显著降低。以芽孢杆菌为例，经索拉胶诱导后其对尖孢镰刀菌的拮抗作用明显增加。经索拉胶预处理的染病土壤中黄瓜成苗率相比于对照组显著提高，而发病率显著下降。索拉胶对土壤的作用随着添加量增加更加明显。经索拉胶水解产物处理的拟南芥植株对土传病菌的抗性显著增强。研究证明，利用外源诱导剂调节土壤微生物群落结构具有改善土壤品质的作用，该方法是一种较为可行的土传病害防控技术。本研究的结果可以为土传病原真菌的生态防治提供理论依据。