Objective This study aimed to screen and identify strains with strong antagonistic effects against wood-rot fungi from the rhizosphere soil of healthy Pinus koraiensis, to provide microbial resources for biological control in wood preservation.

Method Rhizosphere antagonistic bacteria were isolated from Pinus koraiensis rhizosphere soil using the dilution plate method. Antibacterial strains with the best inhibitory effects were screened using the plate confrontation method and the filter paper method, targeting two typical pathogens of wood decay of Trametes versicolor (Tv) and Gloeophyllum trabeum (Gt). The isolated strains were identified based on morphological, physiological and biochemical characterization, and 16S rDNA sequence analysis. The tube-disc method was used to determine the antibacterial activity of the fermentation broth and sterile fermentation supernatant from the target strain against two species of wood-rot fungi.. Wood specimens were treated with the sterile fermentation supernatant of the target strain to evaluate its wood preservative efficacy; changes in hyphal morphology were observed using scanning electron microscopy (SEM) to preliminarily investigate the mechanism of antimicrobial action.

Result The results showed that five antagonistic strains were screened from the rhizosphere soil of Pinus koraiensis. These five antagonistic bacteria exhibited varying degrees of inhibitory effects against the two wood-decay fungi, with strain NF-25 demonstrating the strongest antagonistic activity against Tv and Gt, with inhibition rates of 85.34% and 84.10%, respectively. Based on morphological characteristics, physiological and biochemical properties, and 16S rDNA sequence analysis, NF-25 was identified as Bacillus velezensis. The inhibitory effect of the NF-25 sterile fermentation supernatant on the two wood-decay fungi was slightly weaker than that of the fermentation broth. SEM observations revealed that NF-25 may inhibit the growth of wood-decay fungi by disrupting their cellular structure of their hyphae. Results from the wood preservative tests on wood specimens indicated that the NF-25 sterile fermentation supernatant effectively reduced the rate of mass loss in the test specimens and limited the spread of mycelium within the wood..

Conclusion A strain of antagonistic bacteria, NF-25, which exhibits good inhibitory effects against the wood-decay fungi Tv and Gt, was isolated from the rhizosphere soil of Pinus koraiensis, the bacteria was screened and identified as Bacillus velezensis. Its fermentation broth and sterile fermentation supernatant can interfere with the growth and development of Tv and Gt hyphae. The sterile fermentation supernatant of NF-25 can effectively inhibit wood decay. This study provides a potential source of antagonistic bacteria for biological control of wood decay.