Abstract: To explore biocontrol resources for cotton Verticillium wilt and evaluate the potential application of myxobacteria in managing this disease, we utilized antagonistic activity of mycobacterial strains previously isolated and preserved in our laboratory against Verticillium dahlia were assessed using confrontation culture, mixed culture and dual culture methods, and strains with strong antagonistic effects selected. The efficacy of mycobacterial fermentation broth and solid bacterial formulations against cotton Verticillium wilt was evaluated under greenhouse conditions, along with their impact on cotton growth. Morphological and molecular biological techniques were employed to identify the biocontrol potential of the selected mycobacterial strains. The results demonstrated that the four selected mycobacterial strains effectively preyed on V. dahliae hyphae, inhibited spore germination, and exhibited antibacterial activities through multiple mechanisms. Pot experiments revealed that the fermentation broth of these strains had control effects on cotton Verticillium wilt, with the efficacies ranging from 11.56% to 38.23%. However, efficacies of solid bacterial formulations of strains KS01, NSE37, NSE41 and KY01 on cotton Verticillium wilt were 79.83%, 77.02%, 66.57% and 58.99%, respectively. Based on morphological and molecular analyses, the strains KS01 and KY01 were identified as Myxococcus sp., and strains NSE41 and NSE37 as Cystobacter sp.. The above results showed that four mycobacterial strains had biocontrol potential against cotton Verticillium wilt.

Key words: myxobacterium, cotton Verticillium wilt, predation, screening, biological control