Screening and Identification of Antagonistic Bacteria against Fusarium Wilt of Cucumber and Preliminary Study on Its Antifungal Effect

PurposeTo screen high effective antagonistic bacteria of cucumber fusarium wilt and to study its antimicrobial activity.

MethodsThe antagonistic bacteria were screened from greenhouse soil samples by plate confrontation method, physiological and biochemical tests and 16S rDNA sequencing analysis were performed on the strains with the highest bacteriostatic rate, the antifungal effects were studied by plate inversion method, hollow glass and HPLC.

ResultsA total of eight strains of antagonistic bacteria (XN-1-XN-8) were screened, and XN-3 had the highest inhibitory rate. The results of analysis and comparison in NCBI database showed that XN-3 had the highest homology similarity with 16S rDNA sequence of Bacillus amyloliquefaciens (99%). XN-3 could produce volatile compounds which had antifungal effect. XN-3 could make the mycelia curl, shorten their length, and the microscopic morphology of mycelia expand and bend unevenly, the growth of branching mycelia was blocked, and chlamydospore was generated, its extracellular substance reduced the spore germination rate by 89.01%. HPLC chromatogram showed that the components in peak A-2 had obvious antifungal effect.

ConclusionThe isolated antagonistic bacterium XN-3 was Bacillus amyloliticus, which had a strong antifungal effect on Fusarium oxysporum. It could inhibit mycelial growth and spore germination by extracellular substances, laying a foundation for further study on its biocontrol mechanism.