Kernel volatiles of some pigmented wheats do not elicit a preferential orientation in Sitophilus granarius adults. Journal of Pest Science

The granary weevil, Sitophilus granarius (L.) (Coleoptera, Dryophthoridae), is a primary pest of stored cereals worldwide. To identify possible sources of wheat resistance toward this pest, two commercial durum and bread wheat varieties with yellow pericarp were compared with anthocyanin-pigmented durum and bread wheat genotypes that have never entered commercial production. The composition of the kernel head-space volatile organic compounds (VOCs) and the olfactory responses of granary weevil adults to these kernel VOCs were investigated. Head-space solid-phase micro-extraction and gas chromatography–mass spectrometry analysis highlighted 17 and 13 kernel VOCs from durum and bread wheats, respectively. These compounds mainly included aldehydes and alcohols, and to a lesser extent, terpenes and benzene derivatives. Quantitative and qualitative differences were seen between the odor profiles of yellow and pigmented wheat kernels. In two-choice behavioral bioassays, granary weevil adults were significantly attracted by the kernel odors from the yellow commercial wheat varieties and their hexane extracts, but not by those of the pigmented wheat genotypes and their hexane extracts. Electroantennography confirmed the presence of VOCs in all of the hexane extracts that stimulated the olfactory system of both sexes of the granary weevil in a dose-dependent manner. Thus, differences among the odor blends were responsible for the different olfactory responses of granary weevils to the yellow and pigmented wheat kernels. These differences in VOC emissions and olfactory responses induced in granary weevils by the yellow and pigmented wheat kernels can be exploited to characterize resistance mechanisms associated with different genotypes and to incorporate resistance into improved varieties.