Abstract: The gut symbiotic fungus MF08 of Vespa mandarinia Smith was selected as the research object. The fungus was identified through morphological observation and ITS sequence analysis, and the herbicidal activity of its fermentation products was systematically evaluated. The fermentation products were extracted with petroleum ether, ethyl acetate, and n-butanol, yielding four crude extracts including an aqueous phase. The inhibitory effects of these crude extracts on root growth of Amaranthus retroflexus and Echinochloa crusgalli were determined using a petri dish bioassay. The ethyl acetate phase crude extract was further isolated and purified by silica gel column chromatography, thin-layer chromatography, and dextran gel column chromatography to obtain metabolites, whose structures were identified by nuclear magnetic resonance spectroscopy and mass spectrometry. The results indicated that strain MF08 was identified as Curvularia lunata. At the test concentration of 100 μg/mL, the ethyl acetate phase crude extract exhibited the best inhibitory effect on root growth of Amaranthus retroflexus and Echinochloa crusgalli, with inhibition rates of 77% and 88%, respectively, comparable to the activity of the positive control 2, 4-dichlorophenoxyacetic acid (with inhibition rates of 90% and 96%, respectively). Metabolite 1 and metabolite 2 were further isolated from this ethyl acetate phase; through structural identification,metabolite 1 was determined to be ethyl 2-acetyl-3,5-dihydroxyphenylacetate, and metabolite 2 was methyl 2-acetyl-3,5-dihydroxyphenylacetate. However, neither of them showed herbicidal activity at the same concentration.

Key words: gut fungi of Vespa mandarinia Smith, Curvularia lunata, bio-derived herbicides, herbicidal activity