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 <i>Harposporium anguillulae</i> YMF1.01751, with the expectation of discovering valuable <i>Meloidogyne incognita</i> 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 <i>M. incognita</i>, corn meal agar (CMA) medium was determined as the scale-up fermentation medium. Twelve metabolites (<b>1</b>-<b>12</b>) were isolated from the fermentation products, and compound <b>1</b> was identified to be a new cyclic tetrapeptide. The activity assay results showed that phenylacetic acid (<b>11</b>) had good nematicidal activity at 400 μg/mL, and the mortalities of <i>M. incognita</i> were 89.76% and 96.05% at 12 and 24 h, respectively, while the mortality of canthin-6-one (<b>2</b>) against <i>M. incognita</i> was 44.26% at 72 h. In addition, the results of chemotaxis activity showed that 1-(1<i>H</i>-indol-3-yl)ethanone (<b>10</b>) possessed attraction activity towards <i>M. incognita</i>. At the tested concentrations, cyclo-(Arg-Pro) (<b>4</b>) and cyclo-(Val-Ile) (<b>7</b>) showed an avoidant response to <i>M. incognita</i>. This study provides insight into the nematode-active compounds of <i>H. anguillulae</i> origin and offers new opportunities for the development of RKN biocontrol products.