Objective  Endophytic bacteria with antagonistic action on oil tea anthracnose pathogen Colletotrichum fructicola were isolated from the fruit of Physali alkekengi, followed by the study on the antibacterial mechanism of the strain on the pathogen of Camellia oleifera anthracnose. It is expected to provide a theoretical basis for the field control of Camellia oleifera anthracnose.

  Method  In this study, fourteen strains of bacteria were isolated from fruits by tissue separation isolation, and then three strains of bacteria with significant inhibitory effects on the pathogen of Camellia oleifera anthracnose were obtained with plate-screening method, including the strains of DLSB-1, DLSB-4 and DLSB-13. Subsequently, combining strain morphology, physiological and biochemical characteristics and 16S rDNA sequence alignment analysis, the strain was identified. Furthermore, based on the above test, whether the biocontrol strain can produce protease, cellulase and β-1,3-glucanase was determined, along with the observation of the mycelial growth of pathogenic hyphae fungus by antagonistic bacteria sterile fermentative liquid with microscope, and the indoor control effect of Camellia oleifera seedlings was measured indoors.

  Result  It was found that all three strains of Bacillus sterile fermentative liquid could inhibit the normal growth of the pathogenic hyphae of Camellia oleifera anthracnose, thus making it tip-expanding, deformity and distorted. Besides, protease and cellulase could be produced, while β-1,3-glucanase could not be produced; when compared 5 concentrations (0.6 × 10⁸, 1.0 × 10⁸, 1.4 × 10⁸, 1.8 × 10⁸, 2.2 × 10⁸ cfu/mL) of sterile fermentative liquid with control, it was found that the antibacterial effect on the pathogen of Camellia oleifera anthracnose was significant (P < 0.05), with the highest level of 81.14%. Moreover, the control effects of 5 concentrations of sterile fermentative liquid of strain DLSB-4 on potted Camellia oleifera seedlings were 40.2%, 43.9%, 57.7%, 68.7% and 71.1%, respectively. All these show that there is a positive correlation between good control effects as well as the concentration of sterile fermentative liquid and the control effect.

  Conclusion  The three strains of biocontrol bacteria could produce antagonistic enzymes which inhibiting the growth of pathogenic bacteria hyphae of Colletotrichum fructicola, thus reducing the incidence of Camellia oleifera anthracnose.