Fruit volatiles mediate differential attraction of Drosophila suzukii to wild and cultivated blueberries

Abstract

Native to the northeast USA, highbush blueberry is a crop domesticated for close to 100 years and that has been selected mainly for high yields and bigger fruit. We hypothesized that, due to domestication and associated agronomic selection (i.e., cultivation practices), cultivated blueberries differ from their wild ancestors in fruit volatile emissions, affecting the response of a frugivorous pest. To test this hypothesis, we compared the attraction of adult spotted-wing drosophila (Drosophila suzukii) to wild and cultivated blueberry fruit volatiles in choice assays. We also conducted headspace volatile chemical analysis and electroantennographic detection (EAD) analysis to identify and quantify any antennally active compounds. For this, fruit from wild and cultivated blueberries, growing in proximity, was sampled from six farms located in the Pinelands National Reserve (New Jersey, USA)—a blueberry-producing region with a forest understory consisting largely of wild blueberries. On a per gram basis, we found that wild blueberries are more attractive to D. suzukii flies and have higher volatile emission rates than cultivated blueberries. Nine EAD-active compounds from wild blueberries (isobutyl acetate, ethyl butyrate, ethyl 2-methylbutyrate, ethyl 3-methylbutyrate, hexanal, isoamyl acetate, 3-hydroxybutanone (acetoin), 6-methyl-5-hepten-2-one, and 1-hexanol) were attractive individually and as a blend to D. suzukii flies. However, a 4-component blend composed of isoamyl acetate, acetoin, 6-methyl-5-hepten-2-one, and 1-hexanol was more attractive to D. suzukii than the 9-component blend. Altogether, our results show that the domestication/cultivation of blueberries is associated with lower rates of fruit volatile emissions, which has resulted in decreased attraction of a frugivorous pest, D. suzukii.