Studies On Optimization Of Fermentation Conditions And Biocontrol Effects Against Bacterial Leaf Blight Of Kiwifruit Of Bacillus MC67

Bacillus MC6is isolated from rhizosphere soil of kiwi fruit by408lab of the College of Life Sciences of Northwest Uinversity. Strain MC6showed antagonistic activity against bacterial leaf blight of kiwifruit. This disseration is focused particularly on studies on Microbial Classification and identification, mutation induced by He-Ne laser, fermentation condition optimization, test of stability of fermentation broth, control efficacy of Bacillus MC67against bacterial leaf blight of kiwifruit in the greenhouse. The main results are as follows:According to its morphological, physiological and biochemical characteristies and16SrDNA sequence analysis, Strain MC6was identified as Bacillus megaterium. Through the experiment of antagonistic activity against bacterial leaf blight of kiwifruit, the data shows that the antibacterial function of MC6was best and inhibition zone has the diameter of12.8mm. Using the output power of10mw He-Ne laser to irradiate strain MC6after15min, the mutant MC67was elected from the antagonistic mutants, through continuous cell culture mutant MC67, genetic traits were stable.Integrating the results of A660and inhibition rate, the excellent medium and the optimum medium were selected. Then the results of range analysis and variance analysis were suggested that the optimal fermentation conditions were given. The favorable condition was: fermention time30h, fermention temperature35℃, rotation speed150rpm, original pH7.0, inoculum of0.5%. The first study on the antagonistic mechanism of the filtrate of mutant MC67fermentation showed it not only restrained the growth and propagation of the pathogen, but also reduced the pathogen’s pathogenicity greatly. The study also revealed that the filtrate of mutant MC67fermentation could increase activities of plant protective enzyme (SOD and POD) in kiwifruit.The stability of the filtrate of MC67fermentation inhibitive effect was studied preliminarily. Results showed that it had a high activity to heat, acid and proteinase K and ultraviolet light but it is less stable to alkali, especially under the strong alkali. We concluded preliminarily that antimicrobial active ingredient of the filtrate of MC67fermentation is a lipopeptide substances. Pot experments in greenhouse showed that the cell-free filtrate of MC67fermentation have a good control efficacy to bacterial leaf blight of kiwifruits in seedings after inoculated with pathogen. Using strain MC67cell-free filtrate Oh,24h and48h defore inoculation, respectively investigated7d after inoculation that the biocontrol efficacy were76.4%,87.3%and96.6%. Respectively investigated20d after inoculation that the biocontrol efficacy were38.5%,55.9%and81.0%. Plants inoculated with the filtrate of mutant MC67fermentation is no disease, and grow well.