Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2001
Publication Date: 2/1/2002
Citation: Nitao, J.K., Meyer, S.L., Oliver, J.E., Schmidt, W.F., Chitwood, D.J. 2002. Isolation of flavipin, a fungus compound antagonistic to plant-parasitic nematodes. Nematology 4(1): 55-63. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that attack plants, causing ten billion dollars in annual crop losses in the U.S. The general problem addressed in this study is to find new ways of reducing crop losses caused by root-knot and soybean cyst nematodes, the two most economically important nematodes in the U.S. Prior lab research indicated that a specific fungus isolated from soybean cyst nematode inhibited nematode mobility and egg hatch. In this study, ARS scientists isolated the chemical compound responsible for these effects and identified it as flavipin. Flavipin was synthesized in the lab so that it could be tested for effects on nematodes attacking plant roots. In the greenhouse, muskmelon seedlings were treated with root-knot nematodes, and various concentrations of flavipin were applied to the soil. Despite the effects on egg hatch and mobility observed in the lab, the number of nematode galls produced per gram of plant roots increased with flavipin treatment at a 14-day harvest of roots. No effect of flavipin on nematode numbers was found at a later (55-day) harvest. The results are significant because they are one of the first identifications of a compound isolated from a fungus associated with plant-parasitic nematodes; moreover, the results indicate that the compound affected nematode activity in the lab but did not decrease populations in the soil. The impact of the study is to contribute to knowledge about compounds produced by nematode-associated fungi, and to indicate that a combination of active compounds, or a delivery method that inhibits binding to soil, may be required for nematode management. This research will be used by scientists developing environmentally safe methods for managing diseases caused by nematodes.
Technical Abstract: An isolate of the fungus Chaetomium globosum produces culture broths that inhibit 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 gram 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 higher in plants grown in steamed soil.