Abstract:[Background] Fusarium equiseti (Corda) Sacc. caused root rot is one of the principal soil-borne diseases that have resulted in a decline in the production and quality of Saposhnikovia divaricata in recent years. Because of environmental safety and no harm to humans and animals, biocontrol becomes an efficient approach for the prevention and control of plant diseases. [Objective] In order to mine the biocontrol strains with good antagonistic activity against F. equiseti in the rhizosphere soil of S. divaricata. [Methods] The dilution plate method was used to isolate bacteria from the rhizosphere soil. The antagonistic bacteria were identified via the filter paper method and the Oxford cup method. Antibiotic labeling was employed to mark antagonistic bacteria and assess their colonization capacity. Pot experiments were carried out to investigate their ability of mitigating root rot. The morphological, physiological and biochemical parameters, as well as the 16S rRNA gene sequence, were used to assess the taxonomic position. [Results] A total of 157 strains of bacteria were isolated from the healthy rhizosphere soil of S. divaricata, among which the antagonistic bacterial strain SC-119 with strong activity against F. equiseti was screened out. This strain showed an inhibition rate of 68.53% and exhibited strong colonization capacity and a broad antagonistic spectrum. In the pot experiments, SC-119 showed the control effect of 67.39%, which was 29.03%, 32.26%, and 16.13% higher than that of Trichoderma harzianum, Bacillus subtilis, and mancozeb, respectively. Finally, strain SC-119 was identified as Bacillus atrophaeus. [Conclusion] B. atrophaeus SC-119 has good antagonistic effect and biocontrol potential against F. equiseti, serving as an effective source for the biocontrol of root rot in S. divaricata. The findings of this study facilitate the development and utilization of strain SC-119.
