Abstract:[Background] Fusarium solani-induced root rot poses a threat to the sustainable growth of the Bletilla striata industry. Currently, chemicals remain the primary means for prevention and control of this disease, while their continuous use and accumulation in the environment adversely affect the quality of medicinal materials, the ecosystem, and human health. [Objective] To develop a biocontrol agent against root rot and understanding its inhibitory mechanism for sustainable growth of the B. striata industry. [Methods] Bacteria were isolated from the rhizosphere soil of B. striata. The dual culture method was employed to the screen the strains antagonizing F. solani. The effect of the selected strain on root rot was evaluated by pot experiments. The inhibitory mechanism of the biocontrol bacterium against F. solani was investigated from cellular, physiological, biochemical, and microbiological perspectives. [Results] Five bacterial strains antagonizing F. solani were isolated, among which strain SY16 showed the inhibition rate of (75.3±0.4)% and was identified as Bacillus velezensis. SY16 significantly reduced the incidence and disease index of B. striata root rot, achieving the control efficacy up to 92.86% on day 8 post infection. Moreover, it improved the plant height, tuber fresh weight, and polysaccharide content of B. striata. SY16 competed with F. solani for iron by secreting siderophores, and it disrupted hyphae and inhibited spore germination by releasing amylase and protease. In addition, the strain increased the counts of bacteria and actinomycetes while reducing the count of fungi in the rhizosphere soil of B. striata. [Conclusion] Strain SY16 exhibits significant biocontrol efficacy against B. striata root rot. This study provides theoretical support for the targeted selection of beneficial bacteria to promote the growth and prevent diseases of plants.
