Egg hatch inhibition of root-knot nematodes by Tagetes patula extracts

Tagetes patula (Asteraceae) is a plant cultivated for its ornamental property and biological activities. The objectives of this research were to identify the phytochemicals in T. patula grown in Nigeria and to test the extracts against root-knot nematodes. Phytochemicals in the leaves, stems and roots of T. patula 'Petit' were extracted with different organic solvents and subjected to thin layer chromatography and chemical analyses using standard procedures. In vitro nematocidal assay (Meloidogyne incognita egg hatch inhibition) of the methanol extracts was carried out using 20, 40, 60 and 80% v/v concentrations in transparent glass blocks. Distilled water was used as control. The treatments were applied following a completely randomized design replicated thrice on laboratory bench. Hatched juveniles were counted daily for eight days under a microscope. Percentage hatching was calculated, and the data analyzed using analysis of variance (ANOVA). The extracts from T. patula contained secondary metabolites including alkaloids, terpenoids, steroids, glycosides, tannins and saponins which showed inhibitory activity toward egg hatch of M. incognita. Egg hatch inhibition increased with concentration and contact time of the extracts. The root methanol extract of T. patula showed a consistent egg hatch inhibition at all concentrations suggesting a higher concentration of the active phytochemicals in the roots. Methanol extracts of Tagetes patula leaves, stem and roots can be used to produce potent and environmentally friendly organic nematicides.