Plant parasitic nematodes cause severe damage to crops. Endoparasitic nematophagous fungi (ENF) are a type of important biocontrol fungi, which can cause disease or kill nematodes by producing various spores. As a major ENF, Drechmeria coniospora displays certain potential for controlling plant-parasitic nematodes. In this study, the pathogenicity and secondary metabolites of the endoparasitic fungus D. coniospora YMF1.01759 were investigated. The strain D. coniospora YMF1.01759 had high infection efficiency against nematodes. The process of infecting nematodes by the strain was observed under an electron microscope. Here, 13 metabolites including one new compound 4(S)-butoxy-3-(butoxymethyl)-2-hydroxycyclopent-2-en-1-one (2) were isolated and identified from the fermentation products of D. coniospora YMF1.01759 cultured in a SDAY solid medium. Furthermore, a bioassay showed that 5-hydroxymethylfuran-2-carboxylic acid (1) is toxic to the root knot nematode Meloidogyne incognita and affects the hatching of its egg. Thereby, the nematicidal mortality attained 81.50% at 100 μg/mL for 48 h. Furthermore, egg hatching was inhibited at the tested concentrations, compared with water control eggs. This is the first report on the secondary metabolites of the ENF D. coniospora. The results indicated that D. coniospora could infect nematodes by spores and produce active metabolites to kill nematodes. The biological control potential of D. coniospora against nematodes was expounded further.
Harposporium anguillulae, an endoparasitic nematophagous fungus (ENF), is a model fungus from which the genus Harposporium was established. It can infect nematodes via ingested conidia. In this paper, the morphology and nematode–fungus interaction between Panagrellus redivivus and H. anguillulae were observed by scanning electron microscopy (SEM). The secondary metabolites of H. anguillulae were also studied. Seven metabolites were purified and identified from an ethyl acetate extract of broth and a methanol extract of mycelium. These include a new polyketone 5-hydroxy-3-(hydroxymethyl)-6-methyl-2H-pyran-2-one (1) and six known metabolites (17R)-17-methylincisterol (2), eburicol (3), ergosterol peroxide (4), terpendole C (5), (3β,5α,9β,22E)-3,5-dihydroxy-ergosta-7,22-dien-6-one (6), and 5α,6β-epoxy-(22E,24R)-ergosta-8,22-diene- 3β,7α-diol (7). These metabolites were assayed for their activity against plant root-knot nematode, Meloidogyne incognita, and the results showed that terpendole C (5) had weak nematicidal activity but also that other compounds did not have evident activity at a concentration of 400 μg mL−1. Compound 1 exhibited an attractive effect towards P. redivivus.
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