Study On The Process Of Constructing Soil Microbial Flora By Intercropping Green Manure In Banana Orchard And Its Driving Mechanism

For a long time,banana continuous cropping cultivation mode and unreasonable fertilization methods have caused serious continuous cropping obstacles in banana planting.Banana Fusarium wilt caused by Fusarium oxysporum f.sp.cubense has become a major bottleneck in the development of banana industry in the world.Intercropping with different species was an important way to control soil-borne diseases.In the first part of this study,the effects of intercropping green manure on soil microflora at different growth stages of banana and the incidence of Fusarium wilt of banana were studied by high-throughput sequencing.In the second part,the method of high-throughput sequencing was used to study the effects of diseased plants in continuous cropping banana orchard on soil microbial community of surrounding healthy plants under the action of intercropping with legume green manure.In the third part,the variation of soil microbial community in different spatial soil samples under intercropping green manure was studied by pot experiment and highthroughput sequencing.The main results are as follows:1.Compared with banana monoculture treatment(disease incidence: 30.67%),intercropping with hairy vetch(Vicia villosa Roth)and white clover(Trifolium repens L.)reduced the incidence of banana Fusarium wilt by 20% and 18.67%,respectively.Intercropping with hairy vetch and white clover could increase the richness and diversity of bacterial community in banana soil at different growth stages of banana and reduce the richness and diversity of fungal community.Intercropping with green manure could significantly change the soil bacterial community structure at banana seedling stage,and the change of soil bacterial community structure increased with the increase of intercropping time.However,the soil fungal community structure was relatively stable and did not change significantly at the banana seedling stage,but the soil fungal community structure of different treatments began to separate at the banana budding stage,compared with the banana monoculture treatment at the banana ripening stage,intercropping with green manure treatments have significantly altered the community structure of soil fungi.Intercropping with green manure could effectively change soil chemical properties,increase p H value,organic matter,available phosphorus and nitrogen content in soil.Structural equation model(SEM)analysis showed that the contents of soil p H and organic matter were likely to be the key fertility factors to inhibit banana Fusarium wilt.Intercropping with green manure could significantly reduce the abundance of Fusarium oxysporum in soil at banana budding and ripening stage,and increase the abundance of Aspergillus,Penicillium,Trichoderma,Gp1 and Pseudomonas in soil.Pearson correlation analysis showed that Aspergillus,Penicillium,Trichoderma,Gp1 and Pseudomonas were negatively correlated with disease incidence and Fusarium abundance.SEM showed that Aspergillus,Penicillium and Trichoderma had direct and negative effects on the incidence of fusarium wilt and abundance of pathogen,while Pseudomonas indirectly affected the incidence through Trichoderma.2.The study on the intercropping with green manure blocked the transfer of unbalanced soil microflora between adjacent banana plants showed that,intercropping with green manure could significantly change the soil microbial community structure.Fusarium oxysporum multiplied in the bulk and rhizosphere soil of the diseased plant,and the soil microbial community structure of the plant changed significantly.The diseased plant will assimilate the soil microbial community structure of the surrounding healthy plants,so that the soil microbial community structure of the surrounding healthy plants was gradually transformed into the soil microbial community structure of the diseased plants.Intercropping with white clover could block this assimilation and make the healthy banana plants with white clover interval maintain their own soil microbial community structure.The relative abundance of genus showed that intercropping with white clover could significantly increase the abundance of Aspergillus,Penicillium,Trichoderma,Gp1 and Mortierella in soil,and significantly reduce the abundance of Fusarium oxysporum in soil.Network analysis showed that Penicillium and Trichoderma were more active and had higher connectivity in soils treated with I and IM,while Fusarium oxysporum had higher connectivity in M treatment.Pearson correlation analysis showed that Aspergillus,Penicillium,Gp1 and Mortierella were negatively correlated with Fusarium oxysporum.3.The pot experiment showed that the Chao value and Shannon index of bacterial community in the soil samples near the green manure plant were significantly higher than those near the banana plant,while the Chao value and Shannon index value of the fungal community in the soil sample near the green manure plant were significantly lower than those near the banana plant.There were great differences in the structure of bacterial and fungal communities in different soil samples between banana and green manure plants.From banana plant to green manure plant,the abundance of Fusarium oxysporum in different spatial soil samples decreased gradually,while that relative abundance of Aspergillus,Penicillium,Trichoderma and Gp1 increased gradually.