Nematicidal activity of grammicin produced by Xylaria grammica KCTC 13121BP against Meloidogyne incognita

BACKGROUND The endolichenic fungus Xylaria grammica KCTC 13121BP showed strong nematicidal activity against Meloidogyne incognita. This study aims to identify the nematicidal metabolites and to evaluate the efficacy of the strain as a biocontrol agent under pot and field conditions. RESULTS Bioassay-guided fractionation and instrumental analyses led to grammicin being identified as the nematicidal metabolite. Because patulin is a mycotoxic isomer of grammicin and is known to have strong antibacterial and cytotoxic activities, several biological activities of the two compounds were compared. Grammicin showed strong second-stage juvenile killing and egg-hatching inhibitory effects, with an EC50/72 h value of 15.9 μg/mL and EC50/14d value of 5.87 μg/mL, respectively, whereas patulin was virtually inactive in both respects. Patulin was strongly active toward various phytopathogenic bacteria in vitro, whereas grammicin was weakly so. Patulin at the concentration range of 0.1–10 μg/mL also showed dose-dependent cytotoxicity toward the human first-trimester trophoblast cell line SW.71, whereas grammicin was not toxic toward this cell line. In pot and field experiments, a wettable powder-type formulation and fermentation broth filtrate of X. grammica KCTC 13121BP effectively suppressed the development of root-knot nematode disease on tomato and melon plants. CONCLUSION The results suggest that X. grammica and grammicin may have potential applications for control of root-knot nematode disease of various crops.