Isolation, identification and biocontrol potential evaluation of bacterial strain HZ-61 against tomato gray mold.

To address the issues of resistance and environmental pollution caused by over-reliance on chemical pesticides in the control of Botrytis cinerea, this study aimed to isolate efficient biocontrol bacteria from unique habitats for the development of new resources for green control. Antagonistic strains were isolated from facility agriculture soil on the Qinghai-Tibet Plateau. Their taxonomic status was determined through morphological, physiological, biochemical, and comprehensive molecular identification based on 16 S rDNA and gyrB gene sequences. The antifungal activity and biocontrol potential were evaluated using plate confrontation assays, in vitro fruit protection tests, and microscopic observation. Moreover, culture conditions including carbon source, nitrogen source, temperature, salinity, and pH were systematically optimized. A highly effective biocontrol strain, HZ-61, was isolated and identified as Bacillus pumilus. This strain exhibited an inhibition rate of 75% against B. cinerea in plate assays and achieved a control efficacy of 94.12% in detached fruit tests. It also induced extensive hyphal fragmentation and deformation in the pathogen. Optimization of culture conditions revealed that the optimal carbon source was yeast extract, the optimal nitrogen sources were peptone or tryptone, the optimal growth temperature was 28 °C, the optimal salinity was 1% NaCl, and the optimal pH was 7.0. Strain HZ-61 demonstrated remarkable antifungal activity and biocontrol potential against B. cinerea, providing a preliminary theoretical basis and a key microbial resource for the development of efficient and environmentally friendly microbial agents.