Volatile fatty acids from whey volatilome as potential soil fumigants to control Meloidogyne incognita

Abstract

Organic residues emit volatile organic compounds (VOCs) that are toxic to plant-parasitic nematodes (PPNs). In this study, we demonstrated that whey produced by cow milk emit VOCs that are toxic to Meloidogyne incognita second-stage juveniles (J2), causing immobility above 80% and significant (P < 0.05) mortality compared to controls. The analysis of the volatilome done by gas chromatography coupled with mass spectrometry revealed 28 compounds, predominantly carboxylic acids and esters. Four of those volatile fatty acids (VFAs), namely acetic acid, octanoic acid, ethyl octanoate, and isovaleric acid, were chosen to further studies. The four tested VFAs were toxic to M. incognita J2, with lethal concentration values required to kill 50% of the nematode population (LC50), ranging from 134.30 to 236.08 μg mL−1. However, on eggs, only acetic acid and ethyl octanoate were consistent with J2 hatch inhibition, reaching 80% at a concentration of 1000 μg mL−1. In a greenhouse assay, when the VFAs were applied as soil fumigant, M. incognita infectivity and reproduction were significantly (P < 0.05) reduced compared to the negative control (water). Among them, ethyl octanoate application reduced (P < 0.05) the number of eggs to the level of the commercial fumigant dazomet. Overall, the volatile compounds released by whey were toxic to M. incognita J2 and contained a great diversity of molecules. Among the VFAs, ethyl octanoate stood out and showed the potential to be used in future field studies.