Research On The Mechanisms Of Mitigate Continuous Obstacle Of Banana Orchard With Serious Wilt Disease By Combined Pepper-banana Rotation Together With Application Of Bio-organic Fertilizer

The continuous cropping obstacle was closely related to the soil micro-ecological environment, especially the soil microbial community structure, and improving the soil microbial flora was the key to mitigating continuous cropping obstacle. In this study, the continuous banana orchard with serious wilt disease was taken as the research object, and the effects and mechanisms of mitigating banana continuous cropping obstacle were studied by using the method of pepper-banana rotation together with bio-organic fertilizer.The main results were obtained as follows:(1) The root exudates and residue extracts of pepper had significant inhibitory effect on the growth of FOC4 mycelium, and the inhibition effect of 20mg·mL-1 root exudates and the 10% residue extracts were most significant, with the inhibitory rate were 20% and 69.6% respectively.(2) The pepper residues significant promoted the growth of banana.Compared with banana residue treatments, added pepper residue by 2%(w/w) to both high and low wilt disease incidence soil could reduce the banana wilt disease incidence and disease severity index and the amount of culturable fusarium in rhizospheric soil of low disease incidence as well as bulk soil of high disease incidence were reduced significantly. The pepper residue treatment also increased the amount of culturable pseudomonas in both of the two soil types. Soil pH, the content of available nitrogen and available phosphorus were increased in pepper residue treatments, and the content of available phosphorus was significant in high disease incidence soil. But the content of available potassium was reduced, significantly in low disease incidence soil.(3) The growth of banana was promoted in pepper treatment, significantly. Compared to the banana continuous crop orchard soil, after replant banana the pepper rotation soil treatment had significant increase the amount of culturable benefits microbial such as bacteria, bacillus and actinomycetes in both rhizospheric soil and bulk soil, the amount of culturable pseudomonas in bulk soil was increased significantly, too. At the same time, the amount of culturable fusarium in both rhizospheric soil and bulk soil were decreased. Soil pH, the content of organic matter and available phosphorus was increased in pepper treatments, significant in the content of available phosphorus. While, the content of available potassium was reduced.(4) Next-generation sequencing of the 16S rRNA genes and ITS sequencing using the MiSeq platform showed that after rotated by pepper for one year, the relative abundance of Gemmatimonadetes and Zygomycota in rhizospheric soil were significant increased in PB,and the relative abundance of Firmicutes and Chytridiomycota in bulk soil were significant increased in BB and BO, and they were positively related to the relative abundance of pathogen Fusarium in rhizospheric soil. The clone library identified the percentage of FOC4 in rhizospheric soil that PO was lowest with 0%, PB and BB obtained the percentage by 1.25% and 20% respectively, while the BO was the highest with 22.5%. The amount of culturable bacteria, actinomycetes and pseudomonas in rhizosphere of PB were higher than BO, while the amount of culturable fusarium in rhizospheric soil and fungi in bulk soil were both higher than BO. The soil pH, available nitrogen and available potassium of PB were higher than BO, significantly.(5) After rotated with pepper, the relative abundance of Acidobacteria in rhizosphere was increased and the Ascomycota, Basidiomycota and Firmicutes in bulk soil of PB were reduced. At the same time, the relative abundance of Fusarium was decreased both in rhizospheric soil and bulk soil of PB, while the relative abundance of some non-pathogen microbial such as Penicillium, Trichoderma, Pseudomonas and Aciditerrimonas was increased. The clone library identified the percentage of FOC4 in replant banana rhizospheric soil that PO was the lowest with 7.5%, PB and BB obtained the same percentage by 7.5%, while the BO was the highest with 42.5%. The amount of culturable fusarium, fungi and bacillus in rhizosphere of PB were significantly higher than BO, while the amount of culturable actinomycetes was lower than BO. The amounts of six culturable microbials in bulk soil of PB were reduced than BO, and all achieved the significant level except for fusarium. Soil pH, the content of organic matter, available nitrogen, available phosphorus and available potassium in PB were higher than BO, and significant in the content of available phosphorus.For the wilt disease incidence of replant banana, each treatment was significant different with others. PB was the lowest with 25%, and the other three treatments PO, BB,BO were 36.7%, 48.3% and 73.3%, respectively.