Volatile molecules of Fusarium oxysporum strain 21 are retained in water and control Meloidogyne incognita

Dissolution in water of volatile organic compounds (VOCs) emitted by microorganisms may explain, in part, the distribution of VOCs throughout the soil, and thus the process of exposure of plant-parasitic nematodes (PPN) to these molecules. Water was exposed for short periods (0.5-24 h) to the VOCs emitted by Fusarium oxysporum strain 21 (Fo-21). Water exposed to VOCs caused 100% immobility in second-stage juveniles (J(2)) of Meloidogyne incognita. In addition, inoculation of J(2) in tomato decreased infectivity up to 70% and reproduction up to 65%. Application of water exposed to VOCs in substrate infested with M. incognita J(2) resulted in a 56% reduction in number of galls and a 49% reduction in the number of eggs. This is the first in vivo experimental demonstration of the toxicity of water exposed to fungal VOCs to a PPN. Gas chromatography-mass spectrometry analysis of the volatiles led to the identification of 28 compounds in the water exposed to the VOCs of Fo-21, and 36 compounds in the emission of fungus. The main classes of compounds emitted by Fo-21 were sesquiterpenes, esters and alcohols. This is the first evaluation of volatile compounds retained in water exposed to fungal VOCs, and which are toxic to a PPN.