甘蔗宿根矮化病罹病株根际微生物群落结构重建及拮抗菌的鉴定与利用研究

Ratoon stunting disease (RSD) is one important disease of for sugarcane all over the world. In general, the infected sugarcanes will show the symptom of growth retardation, such as growing thinner and lower or stunted growth. It causes the production of sugarcanes 800～1000 tons decreasing and 1.5 billion yuan lost every year. Due to the reason of lacking significant symptoms of RSD on the appearance or inside, it is quite difficult to identify only by the appearance. Meanwhile, the pathogen of RSD is also difficult to isolate and culture, and hard to make a diagnosis. As a result, spreading of RSD is very harmful to the sugarcane production. Previous studies have shown that the quantity of soil bacteria decrease and fungi，actinomycetes increase in the rhizosphere of sugarcane infected RSD. Meanwhile, soil bacterial diversity index, richness and evenness index in rhizosphere infected RSD all lower than those of non-infected plants. In other words, unbalanced soil microbial community structure and the degradation of soil fertility in rhizosphere are the main reasons for infected plants. This project is aimed to study on the re-construction of microbial community structure in sugarcane rhizosphere and identification, utilization of functional bacteria. Meanwhile, we also study its functions of antagonism and immunity induction to improve the resistance ability of plant under stress, such as drought, or low content of phosphorus. The aim of this project is offering a theory and technological support for building an environment-friendly in sugarcane production.

甘蔗宿根矮化病（RSD）是普遍存在于甘蔗产区的一种世界性重要病害。罹病株出现蔗茎变矮、变细，生长迟滞等不良症状。宿根矮化病每年造成我国原料蔗减产800～1000万吨，直接经济损失达15亿元以上。由于RSD没有明显的外部和内部症状，单从外观难以鉴定，加之病原菌难以分离和培养检测，使RSD诊断极其困难，导致病害蔓延，对甘蔗生产危害极大。申请者团队前期的研究发现：RSD罹病株根际土壤中可培养细菌数量显著低于健康植株，但真菌和放线菌数量则显著高于健康植株。另外，RSD罹病株根际土壤细菌多样性指数下降。由此推测，甘蔗根际土壤细菌多样性下降、群落结构失衡可能是导致甘蔗植株出现病症危害的主要原因。为此，本项目拟从甘蔗产区土壤中开展RSD拮抗微生物的筛选、分离与鉴定入手，探讨利用拮抗微生物组合重建宿根根际土壤微生物群落结构，发挥拮抗微生物的拮抗功能，为广西甘蔗产业的可持续发展提供理论依据和技术支撑。

宿根矮化病(RSD)严重阻碍我国蔗糖产业的可持续发展。RSD植株根际土壤肥力，以及指示土壤健康状况的细菌多样性和丰富度等指标显著降低；门分类水平，Proteobacteria、Actinobacteria、Gemmatimonadetes和Nitrospirae等优势门类细菌占比降低，但Chloroflexi、Acidobacteria、Firmicutes、Cyanobacteria、Planctomycetes和Bacteroidetes等优势门类细菌占比增加；属分类水平，RSD植株根际土壤中Xanthobacteraceae、Acidothermus、Gaiellales、Roseiflexus、Micromonosporaceae和Nitrospira细菌占比呈倍级降低， Acidobacteria细菌及部分未知菌属占比提高。另一方面，RSD植株根长、总根表面积、总根体积和根尖数均显著下降，氮、磷、钾吸收量显著降低，尤其钾吸收量急剧下降；同时，RSD植株内生细菌多样性下降、特有内生细菌优势菌属数量减少。绿弯菌门(Chloroflexi)和酸杆菌门(Acidobacteria)细菌丰度占比急剧增加；厚壁菌门(Firmicutes)和其它分类细菌占比下降； Pseudarthrobacter、红游动菌属 (Rhodoplanes)等部分优势菌属缺失。甘蔗植株根际土壤肥力下降，根际和植株内生细菌丰富度和多样性显著下降，部分优势细菌门属占比剧变和缺失是甘蔗RSD发生的重要原因。甘蔗间作黄豆是减轻RSD危害，构建甘蔗根际土壤健康微生物组的有效农艺措施。