Identification and antifungal activity of antagonistic bacterium HMQAU140045 against blueberry twig blight

Twenty strains of bacteria were isolated by the plate dilution method from the rhizosphere soil collected from the blueberry plantations in Qingdao, Shandong. Among them, a strain, HMQAU140045, with obvious inhibition effect on the target fungus, blueberry Lasiodiplodia twig blight pathogen-Lasiodiplodia pseudotheobromae, was discovered by the plate confrontation method and mycelial growth rate method. With the concave slide method and mycelial growth rate method, the effects of HMQAU140045 fermentation filtrate on the spore germination and mycelial growth of the target fungus were measured. The results showed that the inhibition rate of the 50 times diluted fermentation filtrate could reach 100%. The result of the detached twig experiment indicated that the control efficacies of different components against blueberry Lasiodiplodia twig blight in the fermentation broth are all above 90%. Bioassay results obtained using the mycelial growth rate method demonstrated that the strain was of broad antifungal spectrum, with obvious antifungal activity against fifteen plant pathogenic fungi, including four blueberry twig blight pathogens. Based on the morphological observation, physiological and biochemical characteristics, and the sequence analysis of gyrB, strain HMQAU140045 was identified as Bacillus amyloliquefaciens. These experimental results demonstrated that the strain HMQAU140045 of Bacillus amyloliquefaciens had good antifungal activity.