ACETIC-ACID - A SELECTIVE NEMATOCIDAL METABOLITE FROM CULTURE FILTRATES OF PAECILOMYCES-LILACINUS (THOM) SAMSON AND TRICHODERMA-LONGIBRACHIATUM RIFAI

The nematotoxic activity, efficient against plant-parasitic species, found in the culture filtrates of two Hyphomycetes: Paecilomyces lilacinus (nematophagous fungus) and Trichoderma longibrachiatum was characterized. Purification was performed by distillation and liquid chromatography and identification by gas-chromatography coupled with a DCI system (dynamic headspace). The active substance has been identified as acetic acid which, produced abundantly during fungal growth in liquid medium (up to 0.044 mols of CH3COOH per culture filtrate litre), inhibited movement of infesting juvenile nematodes. These results were confirmed by comparative studies using the commercial molecule as for the H-1 NMR as the biological tests. The toxic activity appeared only when the carboxylic function was in its undissociated form, hence the real interest of pH when studying this nematicidal activity. A study of the literature confirmed the selective permeability of different cuticle zones of nematodes for non-charged substances (non-polar).