Qualitative and quantitative evaluation of glucosinolates in cruciferous plants during their life cycles

Summary

Glucosinolates produced by Brassica species were investigated in relation to biofumigation, a term used to describe the effects some allelochemicals, including glucosinolate derived products, may have on soil-borne pathogens or other herbivores. Four Brassica species of the U-triangle, namely B. nigra (L.) Koch, B. carinata Braun, B. juncea (L.) Czern. and B. rapa L. were compared with respect to their qualitative and quantitative glucosinolate profiles in roots, stems, leaves and reproductive organs. Plants were monitored at four different development stages and the total glucosinolate content as well as their dry matter production as an indication of their potential biomass under field conditions were determined. Glucosinolate levels of up to 120 ìmol g -1 DM were found in B. nigra and B. juncea, while B. rapa did not show values over 25 ìmol g-1 DM at any stage of the investigated plant life cycles. In the three species at the top of U-triangle, reproductive tissues showed the highest glucosinolate concentration when compared to the rest of the plant parts, while in B. rapa, the roots were the organs with the highest glucosinolate concentration. The glucosinolate profile of the different plant parts of the species studied changed during the growth cycle, showing that the trade-off between glucosinolate profile and biomass production should be optimized in order to maximize the biofumigation effect of a crop. However, further information on other allelochemicals and on the different types of glucosinolate derived products resulting from autolysis or myrosinase catalyzed hydrolysis of glucosinolates at different reaction conditions is needed for the appropriate description of the potential biofumigation effects of different crops.