The Role of Alkaloids as Plant Based Alternative Nematicide for Enhanced Yield

The nemacidal efficacy of Jatropha curcas alkaloids was evaluated in in vitro and screen house studies to control the incidence and severity of the root-knot nematode, Meloidogyne incognita on okra (Abelmoschus esculentus). The use of plant extract as alternative nematicides is becoming widespread and gaining prominence, the lack of scientific validation of the active compounds of such plants has hampered the optimization of its use. Alkaloids was first tested against nematode juveniles (J2s) after 24, 48 and 72 hours of incubation at 0, 5 and 10 ml in in vitro conditions. Results showed that although, nematode mortality was highest (99.3 %) after 72 h incubation period at 10 ml rate of application, there was no statistical difference with mortality (98.9 %) obtained at 5 ml. However, under screen house conditions Alkaloids at 0,1,2,3,4 and 5 ml were applied to potted okra plants inoculated with 1,200 infective (J2) larvae of M. incognita. The observed increases in plant heights and leaf areas in the treated than untreated in both years of study could be attributed to alkaloids induced favourable conditions for optimal plant growth and leaf area. The Alkaloids extracts inhibited the activities of the nematodes thereby allowing the plants to make optimal use of the soil nutrients for growth and development. Results also showed that alkaloids applied at 5 ml /pot significantly (P=0.05) reduced root-galls and increased plant growth parameters on application of root and seed alkaloids than the untreated control in 2019 and 2020 years of study respectively. Root and seed alkaloids also increased Okra pod weight by 71 % (4.02 g) and 67 % (4.26 g) in both years. Leaf alkaloids gave least performance in growth and yield of Okra. These findings elucidated the potential of J. curcas alkaloids as possible good plant based alternative for the control of root-knot nematode on okra. The identification of new classes of pesticides from natural plants to replace the hazardous synthetic nematicides now in use looks promising in light of the crude alkaloids extracts discovered to be active in this study.