FURTHER INVESTIGATIONS INTO THE CHEMICAL BASIS OF INSECT–HOST PLANT RELATIONSHIPS IN AN OLIGOPHAGOUS INSECT, PLUTELLA MACULIPENNIS (CURTIS) (LEPIDOPTERA: PLUTELLIDAE)

Abstract

Samples of nine crystalline mustard oil glucosides including sinigrin were isolated from plant tissues of species in the families Cruciferae and Tropaeolaceae. The isolations were achieved by the use of column chromatography on neutral alumina, cellulose powder, activated carbon; by paper and thin-layer chromatography; and by crystallization from methanol–water mixtures.Feeding responses of fifth instar larvae of Plutella maculipennis (Curtis) were tested on agar–cellulose diets containing individual glucosides at various concentrations in the presence or absence of 0.1 M glucose. The amount of feeding was measured by counts of frass pellets produced by the larvae during the test period. All the above-mentioned glucosides were found to act as feeding stimulants for the larvae of P. maculipennis. However, the relative palatability of these glucosides at the same concentration (20 mg per 10 ml of water in the diet) was found to be in the following order: progoitrin > glucocheirolin = glucoconringiin = glucoerucin > glucotropaeolin = sinigrin = sinalbin > gluconasturtiin = gluconapin. Higher concentrations of the glucosides, gluconasturtiin, and gluconapin were toxic to the larvae.