Isolation and identification of an antagonistic bacterium against Fusarium on lily and its antifungal substances

Abstract:

[Objective] The purpose of this study was to isolate and characterize an antagonistic bacterium against Fusarium on lily and to separate and identify its antifungal compounds. [Methods] Serial dilution method and dual-culture inhibition on agar plate were adopted for screening bacteria antagonistic to Fusarium oxysporum. The bacterial antagonists were rescreened by measuring siderophores-producing potential, hydrolytic enzymes activity and soil colonization. The previously isolated bacterial strain was identified using morphological, physiological and biochemical analyses as well as 16S rRNA gene sequencing. Antifungal substances produced by the antagonists were isolated, purified and analyzed based on bioactivity-guided method together with acid precipitation, flash chromatography and HPLC. [Results] A total of 64 bacterial isolates were obtained from the rhizosphere of filed-grown lily and 386 bacterial isolates were from marine organisms and silt. In a dual-culture inhibition test, 9 isolates displayed the antagonistic activity towards Fusarium oxysporum. Strain 11B91 was obtained by rescreening and identified as Bacillus amyloliquefaciens. Antifungal substances produced by strain 11B91 were speculated to be lipopeptides iturin and fengycin. [Conclusion] Strain 11B91 deserved to be developed a kind of biocontrol agent. This is to certify that bacteria from ocean could have potential for the biological control of pathogens which reside in soil so as to broaden our horizon for the?prevention and control of plant diseases.

Key words:Fusarium oxysporum, Dual-culture inhibition, Siderophores, Soil colonization, Lipopeptides