Bioactive Secondary Metabolites from Harposporium anguillulae Against Meloidogyne incognita

Root-knot nematodes (RKNs) are pathogens that endanger a wide range of crops and cause serious global agricultural losses. In this study, we investigated metabolites of the endoparasitic fungus Harposporium anguillulae YMF1.01751, with the expectation of discovering valuable Meloidogyne incognita biocontrol compounds. Based on results obtained by a liquid chromatograph coupled to a mass spectrometer (LC-MS) of crude extracts under five culture conditions and their nematicidal activity against M. incognita, corn meal agar (CMA) medium was determined as the scale-up fermentation medium. Twelve metabolites (1-12) were isolated from the fermentation products, and compound 1 was identified to be a new cyclic tetrapeptide. The activity assay results showed that phenylacetic acid (11) had good nematicidal activity at 400 μg/mL, and the mortalities of M. incognita were 89.76% and 96.05% at 12 and 24 h, respectively, while the mortality of canthin-6-one (2) against M. incognita was 44.26% at 72 h. In addition, the results of chemotaxis activity showed that 1-(1H-indol-3-yl)ethanone (10) possessed attraction activity towards M. incognita. At the tested concentrations, cyclo-(Arg-Pro) (4) and cyclo-(Val-Ile) (7) showed an avoidant response to M. incognita. This study provides insight into the nematode-active compounds of H. anguillulae origin and offers new opportunities for the development of RKN biocontrol products.