Study On Screening、Biocontrol Mechanisms And Effects To The Biocontrol Of Banana Vascular Wilt

In order to obtain the biocontrol strains having strong antagonism to bananavascular wilt,we screened from9bacterium strains with inhibitory potential whichour laboratory isolated and saved early.Then,we optimized the fermentation mediumand culture conditions with the purpus of improving the antibacterial activity ofantagonistic bacteria.At last,we focused on the study of biocontrol mechanism andeffects to the biocontrol of banana vascular wilt. The results are as follows:1) Screening and identification of the biocontrol strain of banana wilt disease:Wescreened from9bacterium strains with inhibitory potential which our laboratoryisolated and saved early and obtained3biocontrol strains (CS16, CS12, CS32) thathaving a good bacteriostatic effect respectively to three kinds of banana wiltpathogenic physiological race (HN1, HN4, FJ4).And the CS16strain of the three hada good performance to all of the three kinds of banana wilt pathogenic physiologicalrace and was identified as Bacillus subtilis by morphological, physiological andbiochemical characteristics,16S rDNA sequencing.2) Optimization of CS16’s fermentation medium formulation and culture conditionsto improve the inhibited effectiveness of CS16: The results showed that the highestantibacterial activity fermentation medium was60mesh corn flour0.5%,60meshsoybean meal1.5%, K2HPO40.1%and the best optimum culture conditions waspH7.5, culture temperature30℃,triangular bottle fluid volume50ml/250ml,inoculum4%and culture time24h. Using the optimized culture medium and cultivationconditions, CS16’s amount of cell growth was42times as before,reached3.3×109cfu/ml and the antibacterial activity increased7%.3) The biocontrol effect of CS16to banana wilt disease: The results showed that theBacillus subtilis CS16itself played a major role in the inhibition process,while thebacteriostasis of its bacteria-free filtrate was very weak and it can be extracted byethylacetate, using ammonium sulfate salting-out, however,can not be extracted.Thesubstance may be lipopeptide antibiotics.4) Biocontrol mechanism of CS16to banana wilt Fujian4(FJ4): The results showed that CS16’s biocontrol mechanism may be a combination result of competitiveinhibition and antagonism. The main inhibitory mechanism may be nutritionalcompetition, while antagonism only played a supporting role.5) The antimicrobial effects of the mixed culture of CS16, CS12and CS32: Theresults showed that, in addition to CS12and CS16having a very weak inhibition, theother strains’ combinations were fully affinity.When mixed CS12, CS16, CS32toculture, the antibacterial effectiveness had not improved.It was to say that the effect ofmaking the three biocontrol strains mixed was the same as a single strain alone.