Semina: Ciências Agrárias (Aug 2016)
Nematicidal activity of crambe extracts on Meloidogyne spp.
Abstract
Alternative methods for the control of nematodes, such as the use of plant secondary metabolites, can be explored for integrated pest management systems. The objective of this work was to assess the best solvent for obtaining allyl isothiocyanate from Crambe abyssinica leaves, and the effects of this extract on Meloidogyne incognita and M. javanica. Dry leaves of C. abyssinica at 200 mg L-1 were used to prepare extracts by using water (by infusion and grinding), acetone, water + ethanol (hydroalcoholic extraction), methanol, hexane, and chloroform as solvents. Following the evaporation of the solvents, the residue was resuspended in water for use in the experiments. Distilled water and chemical nematicide were used as control treatments. Once the most effective extracts were defined, the following dosages of dried crambe leaves were used: 0, 200, 300, 400, and 500 mg L-1. High performance liquid chromatography (HPLC) was used to quantify the allyl isothiocyanate present in the extracts. After the solvents evaporated, the residues were eluted with water and used in assays with 200 eggs for the hatching test or 200 second stage juveniles (J2) for mobility and mortality tests. The hydroalcoholic extract was the most effective in reducing the hatching of M. incognita and M. javanica juveniles, by 71.6 and 74.4 percentage points, respectively. The mortality of M. incognita and M. javanica in the hydroalcoholic extract was 93.2 and 64.4%, respectively, followed by the methanol extract (17.6 and 34%) and the extract obtained by grinding (9.2 and 28%). The hydroalcoholic extract at 250 mg L-1 showed high nematicidal effect. The HPLC analysis of the extracts revealed that only the methanol and hydroalcoholic extracts had allyl isothiocyanate, indicating that the inhibitory effects on the hatching, mobility, and mortality were not solely attributed to the presence of this compound.
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