Screening and evaluation of marine myxobacteria against sugarcane pokkah boeng

【Objective】The purpose of the study was to clarify the biological control potential of marine myxobacteria from Beibu Gulf of Guangxi against the pathogenic fungi of sugarcane pokkah boeng,and to provide scientific bases and material foundations for the development of biopesticides for the effective control of sugarcane pokkah boeng.【Method】 A total of 62 strains of 12 species of myxobacteria from different marine habitats in Beibu Gulf of Guangxi were used as research objects,and two dominant pathogens of sugarcane pokkah boeng in Guangxi,Fusarium sacchari 9DF-3-2 and FS-2-1,were targeted. The antagonistic effect of myxobacteria on F. sacchari was evaluated by plate confrontation culture method,and the potential active strains were preliminarily screened out. The biological control potential of potential active strains against F. sacchari was evaluated by the dialysis membrane confrontation culture method,mycelia lysis method,and mycelia growth rate method from the aspects of antagonistic action mode and effect on mycelia growth of the pathogen.【Result】By plate confrontation culture method,47 strains of myxobacteria from 62 strains of myxobacteria showed obvious inhibition effect on F. sacchari 9DF-3-2 and FS-2-1,with an active strain rate of 75.8%. Eighteen strains of myxobacteria inhibited two strains of F. sacchari with an inhibitory diameter greater than 1.000 cm,among which the strongest inhibition effect was observed in Myxococcus stipitatus T163 and Melittangium sp. T269. The results of myxobacteria extracellular fermentation broth on F. sacchari mycelium lysis test showed that the extracellular fermentation broth of myxobacteria T163 and T269 had the most significant inhibition effect on the mycelium of two F. sacchari strains. The results of dialysis membrane plate isolation test showed that myxobacteria T269,T163 and T071 still had good inhibition effect on F. sacchari after being isolated by dialysis membrane. The antimicrobial activity determination result of the fermentation extracts of myxobacteria showed that the fermentation extracts of myxobacteria T163 and T269 had good inhibition effect on two strains of F. sacchari,among which the best inhibitory activity was achieved by the fermentation extract of T163 at a concentration of 100.0 μg/mL,and its inhibitory median concentration(EC₅₀)to 9DF-3-2 and FS-2-1 were 13.97 and 84.58 μg/mL,respectively.【Conclusion】The marine myxobacteria T163 and T269 from Beibu Gulf of Guangxi show good bioactivity against F. sacchari,the pathogen of pokkah boeng,and have the potential to be developed into green biocontrol agents.