黄孢原毛平革菌改善切花菊连作枯萎病过程中微生物群落的响应机制

It is well known that when a crop was continuously grown in an area for a long time, fusarium wilt would be found and lower yield might be observed. Cut chrysanthemum is one of the most welcomed cut flowers in the world, and it was also seriously affected by fusarium wilt. It was found that except for the exhaustion of residual soil nutrients, accumulation of phenolic acids and change of microbial community structure are another two causes for the incidence of fusarium wilt. In previous research, Phanerochaete chrysosporium was prepared as antagonist，and could effectively decrease the incidence of disease when applied in continuous Chrysanthemum planting. But the content of phenolic acids accumulated in the soil was not affected during the process, so the microbial community is becoming the focus of attention. Based on above studies, we wish to explore the significantly functional microbes and dynamic expression and regulation of genes in the environment after P.chrysosporium used in soil by metagenomics and metatranscriptomics methods. The research would not only illustrate the mechanism of alleviation for fusarium wilt by P. chrysosporium, but also provide useful guidance and tools for other plants.

长期在一块土地种植单一作物会导致一些作物发生连作枯萎病，轻则减产减收，重则绝收。菊花是销售量最好切花植物种类之一，其生长受到连作枯萎病的严重影响。前人研究表明导致连作枯萎病发生原因除土壤营养成分流失外，更为关键的是自毒酚酸类物质积累和土壤微生物群落改变。我们将拮抗菌黄孢原毛平革菌接入枯萎病发病严重的切花菊土壤，发现其能够有效地降低新生长的切花菊枯萎病的发病率，但过程中并没有有效地降解土壤酚酸类物质,所以土壤微生物群落的改变成为研究的重点。本研究将继续以黄孢原毛平革菌为材料，拟采用宏基因组测序、宏转录组技术重点开展两方面的研究：（1）拮抗菌的加入导致土壤微生物群落结构中的哪些潜在功能类群发生相应结构和丰度改变；（2）功能类群中的活跃类群里哪些转录活性较强基因表达变化对植物生长发挥了作用。旨在通过两方面的研究阐明该拮抗菌防治枯萎病可能的作用机制，同时为其它作物的可持续性发展提供重要理论依据。

通过三代全长16S和ITS测序对切花菊爆发连作枯萎病土样和头茬土土样进行微生物群落结构分析比较，发现两种土样细菌群落结构基本一致，而真菌则差异较为显著。进一步对土壤中能够引起切花菊枯萎病的镰刀菌属物种进行分析，发现两种土样中腐皮镰刀菌和尖孢镰刀菌的丰度最高，而其他几种镰刀菌丰度较小。其中连作土中腐皮镰刀菌丰度远高于头茬土，尖孢镰刀菌在两种土样中差异不大。为了确定病原菌，我们从连作土中分离纯化出腐皮镰刀菌和尖孢镰刀菌，随后进行盆栽致病实验。发现接种尖孢镰刀菌的植株和对照组接水样的植株都没有病征，而接种腐皮镰刀菌的物种出现连作大田枯萎病病征。随后用拮抗菌黄孢原毛平革菌进行拮抗实验，发现有明显效果。同时从连作大田里几株仍然长得好的植株中分离到铜绿假单胞菌和枯草芽孢杆菌，发现都对病原菌有直接的接触拮抗作用，而另一株分离到的黄海芽孢杆菌挥发物对病原菌有明显拮抗作用，后期需要大田实验进一步验证拮抗菌的有效性。