Arthrobotrys oligospora (Fungi: Orbiliales) and its liquid culture filtrate myco-constituents kill Haemonchus contortus infective larvae (Nematoda: trichostrongylidae).

Arthrobotrys oligospora is a nematode-trapping fungus belonging to the family Orbiliaceae and one of the main antagonists of nematodes in soil, including plant and animal parasitic nematodes and free-living nematodes. This species develops three-dimensional adhesive nets in which nematodes are trapped, destroyed and consumed by the fungus. It also possesses other strategies to immobilise, kill and degrade nematodes, i.e. nematode-attractant substances, cuticle adhesion polymers and a number of nematocidal metabolites. The objective of this study was to assess the in vitro nematocidal activity of a strain of A. oligospora through its predatory activity and its liquid culture filtrates (LCF) against the ruminant parasite Haemonchus contortus (HcL3) and to investigate the presence of myco-compounds with potential nematocidal activity. Predatory activity (PA) was assessed in agar plates; 200 HcL3 were placed on agar plates with the fungus and a control group and incubated for 10 days. The LCF confrontation with nematodes was performed in microtiter plates. Two media, Czapek-Dox Broth (Cz-DB) and potato dextrose broth, were assessed. Three concentrations (25, 50 and 100 mg/mL) were assessed at 48 and 72 h (n = 4, per concentration). The experiment was performed in triplicate. The results showed 73.6 ± 2.7% PA and the highest mortality (83%) with the LCF in Cz-DB after 72 h. Gas chromatography–mass spectrometry (GC–MS) analysis revealed that the A. oligospora ethyl acetate phase was composed of 1,2-benzenedicarboxylic acid, bis (2-methylpropyl) ester, (M) 1,4-benzenedicarboxylic acid, bis (2-methylpropyl) ester and (M) decanedioic acid (2-ethylexyl) ester. These compounds could be responsible for nematocidal activity. [ABSTRACT FROM AUTHOR]