| Continuous cropping obstacles in modern agricultural production are becoming more and more serious, which result in soil micro-ecologieal environment deterioration and land Persistenee utilization decrease and seriously restrict the sustainable use of land. Soil microorganism is acknowledged as the main factor for the barrier, changes in its number and species in a certain extent reflect the quality and integrity of the soil. Rich microbial diversity is needed to keep soil fertility and promote plant growth and development.The study was divided into three parts:the field investigation of banana fusarium wilt after crop rotation, pot experiment and field test. The pot experiment included solanaceae vegetable crop rotation treatments and banana continuous cropping control, and banana was taken as tested material. The soil used in pot experiment have been used for continuously planting banana for more than15years. A pot experiment combined with denaturing gradient gel electrophoresis (DGGE) was performed to investigate the effect of three solanaceae crop rotations on the number of cultural rhizosphere microorganisms and soil microbial diversities. Antagonistic bacteria against Fusarium oxysporum f. sp. cubense were screened from different rotation crop rhizosphere soil and identified by16S rDNA. The allelopathy from different plant root exudates and plant extracts on FOC was determined, and the soil properties and bananas growth tendency in rotation soil were measured.The main results are as follows:(1) After the field investigation found that pineapple rotation banana fusarium wilt was15%; The incidence of watermelon, corn, cassava after crop rotation was24%,26%,28%; sunflower, soybean had a relatively higher incidence of38%,36%; Peppers, eggplant, tomato was respectively18%,27%,34%.(2) Rotation increased the number and types of antagonistic bacteria in the soil. Mostly, the number of antagonistic Streptomyces in capsicum rotation soil was significantly higher than in continuous cropping soil of banana, and the average inhibition rate was27.70%. Secondary, the average inhibitory rate of the eggplant crop rotation was26.18%. The identification results of16S rDNA showed that the types of antagonistic bacteria in different crop rotation soils mainly concentrated in the Firmicutes, Proteobacteria, Bacteroidetes, and the most abundant species of antagonistic bacteria is in the rhizosphere soil of capsicum rotation, in which Bacillus genus is the primary species. (3) Pepper, eggplant, tomato rotation improved soil pH and increased the soil organic matter content, nitrogen, available phosphorus, available potassium content of the soil. The soil after rotation promoted the growth of banana, and reduced the incidence of Banana wilt.(4) Three solanaceae crop root exudates and residues on FOC allelopathy showed low concentrations promote, high concentrations of inhibitory effect. And underground parts of plant with the same concentration of plant residue allelopathy over ground part, Allelopathy of plant underground parts with the same concentration is greater than ground part, exudates of allelopathy is larger than the residual; allelopathy followed the order of capsicum> eggplant> tomato> banana.(5) The number of bacteria and actinomyces in soil of chili and eggplant rotation significantly increased, the number of fungi and Fusarium oxysporum decreased, soil A/F and B/F values increased. The analysis of PCR-DGGE fingerprint showed that chili rotation increased the number and types of bacteria, and the richness index, evenness index and simpson index were relatively high. In contrast, banana cropping increased the number and types of fungi, but reduced the uniformity of fungi, and led to a specific fungi species of breeding in soil.(6) Field experiment results showed that the rhizosphere FOC quantity and the incidence of banana fusarium wilt reduced after crop rotation, and the effect of the chili crop roration is the most significant. |
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