Acetic Acid, 2-Undecanone, and (E)-2-Decenal Ultrastructural Malformations on Meloidogyne incognita

The use of natural compounds to control phytonematodes is significantly increasing, as most of the old synthetic pesticides have been banned due to their eco-hostile character. Plant secondary metabolites are now evaluated as biologically active molecules against Meloidogyne spp. but their target site in the nematode body is rarely specified. Herein, we report on the ultrastructure modifications of the Meloidogyne incognita J2 after treatment with nematicidal plant secondary metabolites, that is acetic acid, (E)-2-decenal, and 2-undecanone. The commercial nematicide fosthiazate acting on acetylcholinesterase was used as control. For this reason, scanning electron microscopy and transmission electron microscopy have been employed. The acetic acid mainly harmed the cuticle, degenerated the nuclei of pseudocoel cells, and vacuolised the cytoplasm. The (E)-2-decenal and 2-undecanone did neither harm to the cuticle nor the somatic muscles but they degenerated the pseudocoel cells. (E)-2-decenal caused malformation of somatic muscles. According to the above, the nematicidal compounds seem to enter the nematode body principally via the digestive system rather than the cuticle, since the main part of the damage is internal.