In Vitro Assessment of Aqueous Extracts of Castor Plant (Ricinus communis) against Root-Knot Nematodes (Genus Meloidogyne) Infecting Tomato

Abstract

Root-knot nematodes represent a real problem for tomato cultivation throughout the world. The aim of this study was to develop a method of controlling root-knot nematodes with aqueous extracts of castor bean, and to evaluate the effect of these extracts on these agents. Firstly, a sampling which consisted of taking the roots presenting galls and the soil was carried out in a tomato plantation in the region of Tchologo (Côte d'Ivoire) more precisely at Camp Agropastoral Sika (CapSIKA). The analysis carried out showed that there is a significant difference between the number of nematodes in the soil and in the roots of the samples taken, (p-value<0.05). A large number of nematodes were observed in the roots compared to the soil. Then, the extracted nematodes were used for a pathogenicity test to verify their involvement in the appearance of galls in tomato roots. Galls were observed on inoculated tomato plants following this test. Subsequently, the individuals were exposed to the aqueous extract of castor bean (Ricinus communis) at concentrations of 100, 75, 50 and 25%, the control group was not brought into contact with the aqueous extract of castor bean. Mortality and immobility rates were determined. A significant difference between the number of immobile and dead individuals in the extracts (P<0.05) was obtained following the statistical analyses. The results made it possible to show the nematicidal nature of the aqueous extract of castor bean under controlled conditions (in vitro). This extract could be used for the control of Meloidogyne after testing its effectiveness in open fields.