Abstract: This study aimed to develop an effective and safe biological control agent and to sufficiently explore and make use of beneficial microorganisms. One bacterial strain named CF-2, which was separated from fermented bean curd and showed inhibitory effect on postharvest diseases of honey peaches, was identified based on morphological features, physiological and biochemical characteristics, and 16S rDNA sequence homology analysis. The growth curve of CF-2 and its optimal growth conditions were determined. Subsequently, the antimicrobial activity of CF-2 and its metabolites against four main postharvest fungal pathogens of honey peach (Alternaria alternata, Monilinia fructicola, Cephalothecium sp. and Rhizoctonia sp.) was assessed by plate confrontation method and in vivo experiments. The results showed that strain CF-2 was identified as Bacillus subtilis. At 24-48 h of culture, the growth rate of CF-2 reached a peak, and the optimal pH and temperature for its growth were determined as 7.0 and 37 ℃, respectively. CF-2 showed inhibitory effect on the four fungal pathogens in vitro with an average percentage inhibition of (38.70 ± 9.22)%, and it exhibited the strongest inhibitory effect on Cephalothecium sp. with a percentage inhibition of (52.30 ± 3.67)%. The 24 h fermented broth and its cell-free filtrate and cell suspension also had strong inhibitory effect on all four pathogenic fungi. The average percentage inhibition of the cell-free filtrate was (68.76 ± 5.77)% and it showed the strongest inhibitory effect on A. alternata with a percentage inhibition of (77.41 ± 1.91)%. Compared to the control group, treatment with the cell-free filtrate delayed spore germination of the fungal pathogens by 62-64 h and decreased spore?germination rate by 87.93% on average after 12 d. In in vivo experiments, the 24 h fermented broth of CF-2 and its cell-free filtrate and cell suspension all increased the percentage of marketable fruit compared to the control group, especially the cell-free filtrate, which showed the strongest effect, increasing the percentage of marketable fruit by 29% after 6 d. The above findings indicated that CF-2 and its metabolites had strong inhibitory effect on four main fungal pathogens in honey peach.

Key words: antagonistic bacteria, identification, honey peach, postharvest diseases, antifungal effect