The Biocontrol Mechanism Of Bacillus Marinus B-9987

The geoponic disease was prevented by chemical fungicide usually, but it produced the environmental problem and also contaminated the agricultural products. The biological fungicide was presumed to be no harms to the environment and humankind. The application of biological fungicide depended on the research of the bacterio-mechanism to some extant. The fungistatic activity of Bacillus marinus B-9987 was studied in this paper. The metabolite of B-9987 have an perfect antifungal effect on Fusarium oxysporum, Alternaria solani, Bortrytis cinerea and Rhizoctonia solani. The biocontrol effect on tomato was 85.1% to early blight, 88.4% to grey mold. The biocontrol mechanism elicited by Bacillus marinus B-9987 was systematically investigated as follows:(1)The inducement of defense enzymes by different extracts of B-9987 was investigated. The result showed that the activities of five defense enzymes in each treatment were significantly improved compared to the control. In comparison with other treatment, the fermentation broth presented the highest inducing effect. According to the trends of the enzymes` activities, the inducement can be observed in the third day after sprayed with different extracts, and insisted to the seventh day mostly. The comparative study on the activities of defense enzymes was also obtained under different environmental conditions. According to the result, the B-9987 extracts had an inducing effect on the 5 defense enzymes in tomato leaves. The indoor activities of the enzymes (except superoxide dismutase SOD) was higher than the outdoor enzymes activities, and the fermentation broth show better inducement in the same environmental condition. It can be concluded from the result that the B-9987 extracts had an inducing effect on the defense enzymes in tomato. The inducing effect depended on environmental condition.(2)In the defensive responses of plants towards pathogens, volatiles may play a potential role in plant chemical defense strategies. In our work, the leaves of tomato were treated with fermentation broth and cell free filtration in different dilutions and times. The volatiles in the leaves were analyzed by GC/MS. The results demonstrated that the B-9987 extracts with high dilution increased the amount of total antipathogenic volatiles significantly, 4 and 8 times dilution present higher inducing effect than 2 times dilution. Total volatile compounds, phytoxylipin, terpenoids compounds had an releasing burst between the 9th to 11th in 13 days trend, and the trends were similar to each other. The aromatic compounds enhanced in the 1st to 3rd day, the different trend can be inferred the aromatic compounds may have an relationship with disease resistance metabolism.(3) The fungistatic activities and the effect on the cell morphology, permeability, the composition of cell wall and membrane of Alternaria solani of the metabolites of B-9987 was studied. The results showed that the metabolites have strong antifungal activity with MIC and MFC value being 0.35mg/mL and 5.0mg/mL respectively. Detected the protein and nucleotide in extracellular fluid showed the morphology was affected. According to the analysis result of membrane and cell wall, the metabolites affected the synthesis of glucan but had little influence on ergosterol.All the results show that the Bacillus marinus B-9987 has strong inhibition on plant pathogen, and perfect biocontrol effect on tomato early blight and grey mold. The biocontrol mechanism of B-9987 includes inducing resistant, antagonism and volatile compounds releasing promotion. The Bacillus marinus B-9987 has a bright prospect on the application of biocontrol.