Inhibition of Amaranthus retroflexus by wasp gut fungal isolate Fusarium oxysporum MF06

Abstract:

Abstract:［Objective］ To study the inhibitory effect of wasp gut fungus against the radicle growth of Amaranthus retroflexus for the development of herbicides from microorganisms.［Methods］Eleven strains were isolated from wasp gut．Among them the fermentation broth of strain MF06 showed potent herbicidal activity against A．retroflexus．MF06 was identified by morphological observation and molecular biology identification．Fermentation product was isolated and purified by silica column chromatography，TLC and Sephadex LH-20 column chromatography．Metabolite 1 was obtained from fermentation product，and the inhibitory effect of metabolite 1 against the radicle growth of A．retroflexus was studied．The structure was determined by mass spectrum and nuclear magnetic resonance analyses.［Results］By the morphological observation and ITS sequence analysis，MF06 was identified as Fusarium oxysporum． The ethyl acetate extract of MF06 had strong activity against A．retroflexus with inhibition rate of more than 68% under the concentration of 100 μg/mL． It is better than other polarities crude extracts．Metabolite 1 was separated from ethyl acetate extract，and it was determined as a mixture of fusaric acid and 9，10-dehydrofusaric acid．The mixture is co-crystallizing in a 1:1 molar stoichiometry．It inhibited radical growth of A． retroflexus with IC50 value of (0.51±0.18)μg /mL，comparable to that of 2-(2，4-dichlorophenoxy) acetic acid (0.30±0.14 μg/mL) used as a positive control．［Conclusion］ Strain MF06 could be potentially developed as a microbial herbicide．