Antifungal Substance Produced By Bacillus Subtilis SH7 And Its Biological Control Effect Against Tobacco Bacterial Wilt

The purification, characteristics of the antifungal substances produced by Bacillus subtillis strain SH7 and its biological control effect againet Granville Wilt were studied. In order to make certain what were the optimal medium and fermentative condition in which it made the antagonistic protein.The characteristics and bacteriostasis of B. subtillis strain SH7 were also investigated.All of this conclusions were benefit for the exploitation and utilization of B. subtillis strain SH7 and its antifugal substances.The conclusions also provided the basis of biological control.The results were as follow.1. The optimal medium and fermentative condition of SH7 was researched in this study.The results showed that optimal medium was NA medium.The optimal fermentation condition of SH7 was pH6.0,26℃,100mL/250mL,96h and 170r/min.2. The antibacterial substances of SH7 had strong antagonistic activity on many kinds of plant pathogenic fungi and bacteria.The substance was found to be thermostable. The antagonistic proteinwas insensitive to environment heat such as:at 100℃,121℃20min antagonistic abilities were 83.1%,68.0%.The antagonistic protein was insensitive to mediosilicic,alkaline such as:at pH6.0,pH7.0 its antagonistic abilities were the same,at pH9.0,pH10.0 antagonistic abilities were 86%,88%.It was not sensitive to proteinase K,pepsin and organic solvent.The active protein from B.subtilis strain SH7 have diastatic activity. The antibacterial substances of strain SH7 could to lower the EPS secretory volume of Ralstonia solancearum.3. B.subtilis strain SH7 showed antagonism against R. solanacearum.One of the protein was purified by using ammonium sulfate precipitation following by DEAE Sepharose Fast Flow chromatography and Sephadex G-75.The molecular weight of the protein was estimated to be 33.6KDa by PAGE analysis.4. Control efficacy of the crude protein to tobacco bacterial wilt in greenhouse was 70.8% by injection.In field experiment, control efficacy of B.subtilis strain SH7 to tobacco bacterial wilt was 30.36%, and control efficacy of B.subtilis strain SH7 and 72%hydrophilic powders of Metalaxyl Manganese Zn to tobacco bacterial wilt was 46.86%.