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Biological control of plant-parasitic nematodes in carrot and wheat by the fungus Clonostachys rosea

Mudassir Iqbal: Dept. Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences

<div>Biological control is a promising approach to reduce plant diseases caused by nematodes. We tested the effect of the fungus <em>Clonostachys rosea</em> strain IK726 inoculation on nematode community composition in a naturally nematode infested soil in a pot experiment, and the effect of <em>C. rosea</em> on plant health. The numbers of plant-parasitic nematodes extracted from soil and plant roots decreased by 40 to 73 % when <em>C. rosea</em> was applied, while nonparasitic nematodes were not affected. Soil inoculation of <em>C. rosea</em> increased fresh shoot weight and shoot length of wheat plants by 20 and 24 %, respectively, while only shoot dry weight increased by 48 % in carrots. Light microscopy of <em>in vitro</em> <em>C. rosea</em> – nematode interactions did not reveal evidence of direct parasitism. However, culture filtrates of <em>C. rosea</em> growing in potato dextrose broth, malt extract broth and synthetic nutrient broth exhibited toxicity towards nematodes and immobilised 57, 62 and 100 % of the nematodes, respectively, within 48 h. A metabolomics approach using ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) indicated that culture filtrates of <em>C. rosea </em>contained the compound 10-hydroxy-8-decenoic acid, previously reported to have nematicidal activity. This study demonstrates that <em>C. rosea</em> can control plant-parasitic nematodes and thereby improve plant growth. The most likely mechanism responsible for the antagonism is antibiosis through production of nematicidal compounds, rather than direct parasitism.</div>