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Toxicity Screening of Various Plant Extracts Against Nematode Meloidognye Incognita Chitwood and Radopholus Similis Cobb and Characterization of their Nematicidal Components
Dissertation Abstract:
Solvent extracts of eight plant species were screened for toxicity against two economically important nematode genera, namely: Meloidogyne incognita Chitwood and Radopholus similis Cobb. The plant species were: Anthocephalus chinensis (Lamb.) Rich e Walp, Desmodium gangeticum (Linn.) DC, Artemisia vulgaris Linn., Eichornia crassipes (Mart.) Solms, Leucaena leococephala (Lam.) de Wit, Allium cepa Linn., Allium sativum Linn., and Moringa oleifera Lam.
The extracts showed definite indications of toxicity in immersion bioassay and pathogenicity tests. However, the degree of toxicity varied among the different species. Results favorably compared with toxicity values obtained with the standard pesticides used, namely: Nemacur 10 G (fenamiphos), Temik 10 g (aldicarb), and Rotenone, a pesticidal compound taken from Derris elliptica. Mortality data after 48 hours and percent reduction in hatchibility and infection parameters were the bases for comparison (i.e., number of eggs mass, nematode population in root, and number of galls for M. incognita; and lesion number and nematode population in root and soil for R. similis).
The crude extracts of A. chinesis, E. crassipes, and A. cepa showed outstanding results in the toxicity tests. Subsequently, these extracts were functionated by preparative thin-layer chromatography and purified to isolated the active principle. Separated fractions were again bioassayed on the test organisms to test their nematicidal activity in this purified state. The A. cepa crystals, Fraction 2 of A. chinensis, and Fraction 1 of E. crassipes showed high toxicity.
Characterization of the active components by ultraviolet and infrared spectrophotometry suggested the presence of a ketone in the A. cepa crystal, a phenolic aldehyde in A. chinensis Fraction 2, and a carboxylic acid in E. crassipes Fraction 1, which were responsible for nematicidal activity.
