Breeding Cultivars from Blueberry × Deerberry Hybrids: Progress and Prospects
P. M. Lyrene
Abstract
Vaccinium stamineum (deerberry) is a highly variable diploid species in section Polycodium . Deerberry is native on excessively drained sandy soils from southeastern Ontario, south through the Florida peninsula to Lake Okeechobee, west to eastern Texas and southeastern Kansas. The V. stamineum used in this study were tall plants (2–4 m) native in north Florida, with a plant architecture similar to rabbiteye blueberry ( V. virgatum ). Starting in 2013 with crosses between tetraploid highbush cultivars (section Cyanococcus ) and colchicine-doubled V. stamineum , hundreds of F 1 and thousands of later-generation seedlings were grown and evaluated in high-density field nurseries at Citra in North Florida. The populations studied included F 1 , F 2 , backcrosses to each parent species, and BC 1 × BC 1 seedlings. The goal of the study was to assess the feasibility of introgressing into highbush blueberry cultivars desirable traits from V. stamineum (drought tolerance, red-flesh berries, new flavor components, open flowers with short corolla cups and exserted anthers and stigmas) without introducing horticulturally problematic characteristics (bitter skin, berries that shatter when ripe, difficult vegetative propagation). Vigor averaged very low in F 1 seedlings, higher in F 2 seedlings and in seedlings from backcrosses to V. stamineum , and highest in seedlings from backcrosses to highbush. Most crosses yielded numerous plump seeds, but crosses to produce F 1 hybrids yielded fewer than 10% as many seeds as highbush × highbush crosses. Most vegetative, flower, and fruit traits that differentiate highbush from V. stamineum were intermediate in F 1 seedlings. Backcross seedlings more closely resembled the recurrent parent. Variability in morphological characters was high in every generation, giving much opportunity for selection. Some seedlings from backcrosses to highbush (≈5%) appeared to have the vigor, berry quality, and yield potential required in commercial cultivars. Producing highbush cultivars that strongly express a particular V. stamineum trait might best be accomplished by growing large, segregating F 2 populations from which parents for backcrosses can be selected.