Abstract

An antagonist bacterium ZQ2 was isolated from an apple rhizosphere at Mount Tai in China. The bacterium strongly inhibited the growth of numerous apple phytopathogens in vitro, such as Rhizoctonia solani, Fusarium oxysporum, Fusarium solani, andPhysalospora piricola. The inhibition rates against the different fungi ranged from 55.26 to 88.17. The strain ZQ2 was identified as Brevibacillus laterosporus based on morphology, biochemical tests, and 16S rDNA sequence analysis. The antifungal metabolites produced by ZQ2 were thermally stable even after being maintained at 121°C for 30 min. Meanwhile, the activity against the growth of R. solani was almost unchanged when the culture filtrate was irradiated under ultraviolet (UV) or at pH ranging from 1 to 11, and was only reduced under pH conditions from 12 to 14. When observed under a light microscope, the mycelia of R. solani inhibited by the antifungal metabolites appeared abnormal in growth. The strong antifungal activity and relatively stable active substances of B. laterosporus ZQ2 showed great potential for controlling fungal diseases in apples.

Key words: Brevibacillus laterosporus, characterization, antifungal activity.