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An isolate of the fungus Chaetomium globosum produced culture broths that inhibited in vitro egg hatch and juvenile mobility of root-knot nematode (Meloidogyne incognita) and hatch of soybean cyst nematode (Heterodera glycines). Extraction and bioassay-directed fractionation of the culture broth filtrate determined that flavipin, a low molecular weight compound, was the fungus metabolite responsible for most of the nematode-antagonistic activity. Synthesis of flavipin permitted evaluation of the compound as a suppressor of nematode populations on plants in glasshouse studies. Muskmelon (Cucumis melo) plants in steamed and unsteamed soil were inoculated with root-knot nematodes and various concentrations of flavipin were applied to the soil. Contrary to expectations from the in vitro studies, the number of galls per g of roots increased with flavipin treatment at the 14-day harvest. No effect of flavipin on nematode populations was found at the 55-day harvest. In general, plant growth and nematode populations were greater in plants grown in steamed soil. |
