Screening and identification of Bacillus atrophaeus QH-588 for biological control of cherry leaf spot

【Objective】 Bacterial strains that could antagonize cherry leaf spot were isolated from the rhizosphere soil of Lycium barbarum, so as to provide biocontrol resources for the control of cherry leaf spot.【Method】 The culturable bacteria were isolated from the rhizosphere soil of L. barbarum by dilution plate method. The antagonistic effect of the isolated strains against Colletotrichum salicis, Alternaria alternaria, A. tenuissima was determined by plate confrontation method. Combined with morphological, physiological and biochemical characteristics and phylogenetic analysis based on 16S rDNA, GyrA and GyrB genes sequences, antagonistic bacteriawere identified;the effects of antagonistic bacteria on the mycelial morphology and spores of target fungi were observed under microscope, and the in vitro leaf culture of cherry was selected to determine its prevention and control effect on cherry leaf spot.【Result】 A total of 660 strains of bacteria were isolated from the rhizosphere soil of L. barbarum, of which 10 strains had strong antagonistic effect on the tested pathogens. Among them, the inhibition rate of fermentation broth of 4 strains of bacteria(QH-588, QH-668, QH-667 and QH-664) on the target pathogens exceeded 50.00%. After identification, strain QH-588 was Bacillus atrophaeus, strains QH-664, QH-667 and QH-668 were B. subtilis. Microscopic observation showed that B. atrophaeus strain QH-588 could inhibit the mycelial growth and spore germination of the target pathogen.The results of biological control showed that the fermentation broth of strain QH-588 could prevent and control the target pathogens on the isolated leaves of cherry.【Conclusion】 B. atrophaeus strain QH-588 has the potential of biocontrol against cherry leaf spot.