Effects of glucosinolates and their enzymatic hydrolysis products via myrosinase on the root-knot nematode Meloidogyne incognita (Kofoid et White) Chitw.

The root-knot nematode Meloidogyne incognita (Kofoid et White) Chitw. is responsible for large yield losses in several horticultural crops. Fumigation with chemicals has been efficient in fighting this soil pest, but it clearly shows a negative environmental impact. Thus, it is necessary to find an environmentally friendly alternative to control this nematode and meet the requirements imposed by world regulation to ban some chemical fumigants in the world after 2005. The glucosinolate-myrosinase system, typical of the Brassicaceae family, appears to be an important natural alternative for the control of several soilborne pests and pathogens. The aim of this study was to evaluate, in vitro, the biocidal activity of 11 glucosinolates and their degradation products on second-stage juveniles of the root-knot nematode M. incognita expressed by the nematicidal (LD(50)) and immobilization effects, after 24 and 48 h. None of the intact glucosinolates had any biological effect. After myrosinase addition, their hydrolysis products (essentially isothiocyanates) resulted in highly different biocidal activities. Among the hydrolysis products of the tested glucosinolates, 2-phenylethyl, benzyl, 4-methylthiobutyl, and prop-2-enyl isothiocyanate showed the stronger activity, with an LD(50) at concentrations of 11, 15, 21, and 34 microM, respectively. On the basis of the in vitro test results, new genotypes of Brassicaceae had been selected for high content in the roots of the glucosinolates generating the more active isothiocyanates and their agronomic performances verified in view of a full-field application as catch crop plants. With this aim, the qualitative and quantitative glucosinolate contents in the roots of these potentially nematicidal plants are also reported and discussed.