EFFECTS OF GLUCOBRASSICIN, EPIPROGOITRIN AND RELATED BREAKDOWN PRODUCTS ON LOCUSTS FEEDING - SCHOUWIA PURPUREA AND DESERT LOCUST RELATIONSHIPS

The glucosinolates of a Saharan crucifer Schouwia purpurea (Forskal) ( Brassicaceae) were determined by liquid chromatography. Two of these g lucosinolates and sinigrin were tested for their deterrent effect on S chistocerca gregaria (Forskal) (Orthoptera: Acrididae). Glucobrassicin , three indolyls and epigoitrin were synthesized for this purpose. Epi progoitrin was extracted from Crambe seeds. Choice tests on artificial substrate compared feeding responses to glucosinolates and to related breakdown products released when the plant is eaten. Breakdown produc ts were more efficient in deterring the generalist locust than were gl ucosinolates. Two patterns of dose responses were recorded: glucosidic compounds deterred or stimulated feeding, depending on the concentrat ion tested; aglycones did not stimulate feeding at any concentration. Allyl isothiocyanate, a volatile compound, was a 100-fold higher deter rent than its substrate (sinigrin).