Dimorphism in inflorescence scent of dioecious wild grapevine

Wild grapevine (Vitis vinifera subsp. sylvestris) is the dioecious ancestral form of grapevine, from which the domesticated cultivars have derived (Vitis vinifera subsp. vinifera). Little is known about the floral scent compounds of wild grapevine that is considered as being partly insect pollinated. The knowledge of volatiles released by male and female inflorescence may contribute to the understanding of the pollination biology of this endangered taxon. Inflorescence scents of male and female individuals were collected by dynamic headspace and analysed by thermal desorption-GC/MS. A total of 17 compounds of C5-branched chain alcohols, aliphatics, aromatics, and terpenoids were identified with benzyl alcohol being most abundant in both sexes. Eight of the compounds were sex-specific and differences in 1,2-dimethoxybenzene were most obvious. This aromatic compound was a main constituent in the scent of females (30%), but it did not occur in males. Some of the main compounds of the scent samples are known to be detected by beetles (Cerambycidae) or attract sweat bees (Halictidae) and honey bees (Apis mellifera), all well- known inflorescence visitors in wild grapevine. The data presented here are an important step in understanding the chemical communication between wild grapevine and its inflorescence visitors / potential pollinators.