ChbB increases antifungal activity of Bacillus amyloliquefaciens against Valsa mali and shows synergistic action with bacterial chitinases

Abstract

Apple Valsa canker (AVC), caused by the fungus Valsa mali (Vm), is a serious and persistent disease affecting apple production in China that is difficult to control chemically and agriculturally. In order to develop biological control agents (BCAs) for this disease, an antifungal activity-deficient Bacillus amyloliquefaciens mutant, ED-2544, was characterized using PCR amplification, Southern blotting, and SiteFinding-PCR. The B. amyloliquefaciens ChbB (chitin-binding proteins from B. amyloliquefaciens) and chitinase genes were cloned and heterologously expressed in Escherichia coli. The purified recombinant ChbB and chitinase were used to study antifungal, substrate binding, and synergistic activities. The results show that combining ChbB with chitinase increased the activity of chitinase and its antifungal activity. ChbB and chitinase show a synergistic effect on B. amyloliquefaciens EDR2 activity against Vm. These results provide a theoretical basis for the use of B. amyloliquefaciens EDR2 to control AVC.