Submitted to: Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2003
Publication Date: 5/1/2004
Citation: Meyer, S.L., Huettel, R., Liu, X., Humber, R.A., Juba, J., Nitao, J. 2004. Activity of fungal culture filtrates against soybean cyst nematode and root-knot nematode egg hatch and juvenile mobility. Nematology 6(1): 23-32. Interpretive Summary: Plant-parasitic nematodes are microscopic worms that cause ten billion dollars in U.S. crop losses annually. The problem addressed by this research is to find new methods for reducing crop yield losses caused by root-knot and soybean cyst nematodes, the two most economically important plant-attacking nematodes in the U.S. For this study, ARS and Chinese scientists collected soybean cyst nematode eggs from soybean fields in China. ARS scientists obtained 253 fungal isolates from the nematodes and tested the isolates for production of chemical compounds active against root-knot and soybean cyst nematodes. To do this, the fungi were grown in liquid cultures, and the culture liquids were tested for effects on nematode egg hatch and on movement of newly hatched nematodes. Some fungi produced compounds that stimulated egg hatch, some inhibited egg hatch, and others had no effect. Very few culture liquids inhibited movement of newly hatched nematodes. The results are significant because the study identified fungal isolates that produce compounds active against these nematodes; the impact of the research is that these fungi are now available for chemical identification of the active compounds. This research will be used by scientists developing environmentally safe methods for managing diseases caused by nematodes.
Technical Abstract: Fungi were isolated from soybean cyst nematode (Heterodera glycines) eggs collected in China, and 253 isolates were assayed for production of compounds active against H. glycines and root-knot nematode (Meloidogyne incognita). Fungal isolates were grown for 3 and 7 days in potato dextrose broth (PDB), the culture broths were sterile-filtered to remove fungal biomass, and the filtrates were placed into 24-well tissue culture plates to test for effects on egg hatch and juvenile mobility. Meloidogyne incognita egg hatch ranged from 2% to 121% of egg hatch in PDB controls, and H. glycines hatch was 15% to 224%; activities of filtrates harvested after 3 days and after 7 days were significantly correlated. Only six isolates significantly inhibited juvenile mobility. This study identified fungal isolates capable of producing compounds active against these nematodes. The assay procedure can subsequently be utilized for bioassay-driven identification of such compounds.