Screening small fruit germplasm for resistance to southern populations of invasive spotted wing drosophila, SWD (Diptera: Drosophilidae)

The objective of this study was to develop an effective screening method for evaluating resistance to the spotted wing drosophila (SWD; Drosophila suzukii, Matsumura) in southern-adapted blueberry germplasm including the hexaploid rabbiteye (Vaccinium asheii Reade = V. virgatum Aiton) and the tetraploid southern highbush (V. corymbosum L.) complex hybrid. One hundred berries from 88 blueberry genotypes were examined for the presence or absence of SWD feeding damage or egg laying. In laboratory bioassays using no-choice arenas, clutch size for SWD (number of eggs per fruit) as well as total brood per fruit were assessed after 3 days, and these counts correlated with berry quality attributes that were independently recorded for each cultivar or selection before SWD infestation (berry weight, percentage soluble solids (°Brix), and harvest season (early-, mid-, and late-season harvest)). No antibiosis was be detected among blueberry hosts tested in our experiments; SWD flies laid from 5 to 10 viable eggs per host fruit within 3 days. SWD fecundity (viable eggs) and total brood production was strongly associated with sugar levels in blueberry fruit.