| The banana fusarium wilt caused by F. oxysporum f.sp. cunbense race 4 (FOC-4),could infect almost all banana varieties, which was the cilprit for the banana fusarium wilt in Hannan, it was a vascular bundel of systemtic disease and the chemical method was extremely difficult to control. It is necessary to find an method, which are effective and friendly for the environment, to control this disease. Therefore, biological control set a new research direction. Bacillus subtilis strain B43 was previously isolated by lab. Strain B43 could effectively inhibit a variety of tropical plant pathogenic fungi like FOC-4. In this dissertation, the antifungal substances of strain B43 were studied. In order to control banana fusarium wilt effectively, explore biological control prospects for the strain B43.And provide a theoretical basis for development and applocation in the future.1?The antifungal property of strain B43 against 21 plant pathogens was measured by using the plate dual-culture antagonistic method. The results showed that strain B43 exhibited an effective inhibitory activity against 21 plant pathogens, with the inhibition rates ranging from 38.03% to 85.51%. Among them, for strain FOC-4 was 56.54%, and has a strongest inhibition rate for Trichothecium roseum. B. subtilis strain B43 has a good broad-spectrum antimicrobial properties.2?The experiment was adopted to study the active substance from strain B43, the results showed that the active substance belongs to the exocytosis metabolites, and vast majority existing in the supernatant.3?The single factor experiments was carried in order to study the strain B43 culture conditions shows that LB medium used as the fermented liquid culture medium, the initial pH value of 6.0, with 40% installed volume and 7% quantity of inoculation,shaking table culture 3d(28?, 200r/min), strain B43 showed the best growth level.4?The antifungal substances was extracted by hydrochloric acid precipitation and organic solvent from strain B34, and their stabilities in turn were analyzed. The results shows that, the hydrochloric acid precipitation and the ethyl acetate extract had demonstrated antifungal activity, and the hydrochloric acid precipitation showing a strong antifungal activity compared with the ethyl acetate extract. The hydrochloric acid precipitation extract retained 71.46% antifungal activity after a 150 min exposure to UV,and 72% of that of the control after thermal treatment at 100?. However, the extract no endurance extreme acid and alkali treatments. The suitable pH for the extract to remain stable was ranged from pH 5.0-7.0.5?The PCR products with seventeen primer pairs were cloned and sequenced. The BLAST analysis showed that the srfAB?ituA?ituB?ituD?fenD?yndJ?sfp?mycB?lpa-14 or fenB genes exist in the genome of strain B43. Twenty-four kinds of lipopeptides Surfactin?Iturin?Mycosubtilin?Bacillomycin and Fengycin were identified in the antimicrobial extract by the LC-MS analysis.6?The active substances in the extract were separated and identified by classical column and mass spectrometry and nuclear magnetic resonance(NMR). The results showed that three activity substances were isolated from the ethyl acetate extract, which were 2,6-Dimethoxy-1,4-benzoquinone?Dibenzofuran?1-Dodecanol, the active level was arranged. |
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