Isolation，identificationandfermentationconditionsoptimization of antagonistic bacteria against southern blight on Aconitum carmichaeli

【Objective】 This study screened and obtained antagonistic bacteria with good inhibitory effect on the pathogen of southern blight on Aconitum carmichaeli from Tenebrio moliter，so as to provide strain resources for the biological control of southern blight on A. carmichaeli.【Method】 Using diseased T. moliter as the material，the bacteria with antagonistic effect on southern blight on A. carmichaeli was isolated and screened by dilution coating and plate confrontation methods. The antagonistic bacteria was identified by morphological，physiological and biochemical characteristics and 16S rDNA sequence. With the OD value of bacterial fermentation broth at 600 nm as the index，the culture medium components and fermentation conditions of antagonistic bacteria were optimized by single factor experiment. The control effect of antagonistic bacteria on southern blight on A. carmichaeli was confirmed by pot experiment in laboratory.【Result】 Four strains of bacteria were obtained from T. moliter by dilution coating method. And TS1 strain with greater antagonistic effect against southern blight on A. carmichaeli was obtained by plate confrontation method，with an average inhibitory rate for Sclerotium rolfsii mycelial growth of 68.03%. The TS1 strain was identified as Bacillus subtilis based on its morphological，physiological and biochemical characteristics and the result of 16S rDNA sequence analysis. The optimized medium formula was peptone 10.0 g/L，yeast extraction powder 5.0 g/L and maltose 15.0 g/L. The optimal fermentation conditions were 30 mL of liquid，0.50% of initial inoculum，210 r/min of rotation speed，42 ℃ of temperature，initial pH 9，and 48 h of incubation. The results of laboratory pot experiment and experimental treatment showed that the average control efficiency of TS1 strain against southern blight on A. carmichaeli were 49.39% and 62.97% respectively.【Conclusion】The optimized fermentation scheme can be used to rapidly culture TS1 strain suspensions in large quantities. TS1 strain has a good control effect on southern blight on A. carmichaeli and has the potential to be developed into a biocontrol bacterium for southern blight on A. carmichaeli.