Behavioural responses of Sitophilus granarius (L.) and Rhyzoperta dominica (F.) to odours of old and modern wheat genotypes

Sitophilus granarius (L.) and Rhyzopertha dominica (F.) are among the major stored-product pests worldwide. The identification of low or un-attractive wheat genotypes toward storage pests and their Volatile Organic Compounds (VOCs) profile is useful in breeding programs and in characterization of behaviourally active compounds suitable in developing semiochemical-based control means. Old wheat cultivars are genetic resources useful for breeding purposes. In this study, the VOC profiles of old genotypes, Senatore Cappelli, old Saragolla, Dauno III, and modern wheat varieties, Mec, Ofanto, Svevo, and Faridur, were characterized by headspace - solid phase microextraction (HD-SPME) and gaschromatography coupled with mass spectrometry (GC-MS) and their attractiveness towards S. granarius and R. dominica adults was evaluated in two-choice pitfall bioassays and Y-tube olfactometer, respectively. Sitophilus granarius adults were significantly attracted to odours of all varieties, with females being significantly more attracted by Faridur, Ofanto, Mec, and old Saragolla compared to Svevo. Rhyzopertha dominica males and females exhibited a significant olfactory preference for the odours of Faridur, Mec, and old Saragolla. The olfactory preferences of both species could be related to differences emerged in varietal VOC profiles. The most attractive variety for both species, Faridur, was rich in alcohols, alkanes, and terpenes. Old Saragolla, Ofanto, and Mec were rich in alcohols and organic acids. Dauno III was the richest variety in alcohols and lactones, and the poorest in aldehydes and terpenes compared to other varieties. Svevo showed the lowest amounts of alcohols and the highest value of aldehydes; Senatore Cappelli was rich in aldehydes, organic acids, and alkanes. The possible effects of the differences in VOC profiles on the olfactory preferences of insects are discussed. The study offers new knowledge for further investigation testing VOCs of the most and the lowest attractive varieties to identify effective attractants or strong repellents towards S. granarius and R. dominica.