Studies on the Nematicidal Efficacy of Khaya senegalensis Methanol Leaf Extract on Root-Knot Nematodes of Tomatoes

Root-knot nematode infestations represent a severe agricultural crisis, aggressively diminishing the vegetative growth and harvest yields of vital crops both within Nigeria and on a global scale. This greenhouse-based investigation evaluated the therapeutic potential of Khaya senegalensis leaf extracts in mitigating root-knot nematode damage in tomato plants. To identify candidate botanicals, a localized survey was conducted among farmers in Sokoto State to document traditional plant-based remedies used against suspected nematode attacks. The researchers distributed 300 questionnaires evenly across the state's three senatorial districts. The survey revealed nine utilized plant species, from which three were isolated for experimental focus—representing the most frequently cited botanical from each respective district. For the biological assay, thirty 15 cm open-mouth plastic pots were prepared with sterilized soil. One-week-old, independently raised tomato seedlings were carefully transplanted into these receptacles. With the exception of a designated healthy control group, each seedling environment was artificially infested with 1,000 nematode juveniles. A methanol-derived extract of Khaya senegalensis leaves was then administered to the infected plants at graduating concentrations (100 mg/ml, 200 mg/ml, 300 mg/ml, and 400 mg/ml), alongside an untreated, infected control group. Following a four-week incubation period, researchers evaluated several developmental metrics, including total plant height, root extension, galling severity, and final nematode counts. The data revealed marked physiological improvements across all measured parameters in the extract-treated cohorts compared to the untreated infected plants, with the most robust recovery observed at the maximum dosage of 400 mg/ml. Initial phytochemical analysis confirmed the presence of bioactive constituents, which likely drive the observed parasitic suppression. Nonetheless, comprehensive biochemical modeling is required to isolate the specific phytocompounds responsible for these defense mechanisms across diverse plant species.