Population-level variation in resistance of wild and cultivated blueberries to spotted wing drosophila

Spotted-wing drosophila (Drosophila suzukii, SWD) is an invasive pest that affects many cultivated soft-skinned fruits, including blueberries. While previous studies have identified fruit traits associated with SWD resistance—many of which have been altered through domestication—our understanding of how domestication influences resistance across wild and cultivated populations remains limited. Highbush blueberry (Vaccinium corymbosum), a perennial shrub native to the northeastern United States, was domesticated approximately 100 years ago. In the New Jersey's Pinelands region, domesticated and wild populations coexist. All domesticated highbush blueberries are tetraploid, while wild populations include both diploid and tetraploid genotypes. In this study, we investigated the effects of domestication and ploidy on blueberry resistance to SWD across eight sites in New Jersey. We hypothesized that wild blueberries would exhibit greater resistance to SWD than domesticated varieties, with wild diploids being the most resistant. To test this, we collected blueberries from wild and domesticated populations with varying ploidy levels and analyzed berry traits known to influence SWD resistance. We also conducted insect bioassays to evaluate SWD performance on different berry types. We found that higher ploidy levels were associated with increased susceptibility to SWD, regardless of domestication status. Berry traits differed between domesticated and wild types as well as across ploidy levels and varied by population. These findings suggest that ploidy, rather than domestication alone, may play a critical role in shaping resistance to SWD in blueberries. This research has important implications for breeding programs aiming to develop SWD-resistant highbush blueberry cultivars.