High-density linkage map and QTL analyses for fruit quality traits in the wild blueberry relative <i>Vaccinium stamineum</i>

The wild blueberry relative Vaccinium stamineum offers a rich source of diversity for expanding the genetic pool of cultivated blueberries, and it has also potential for breeding as a crop on its own. Understanding the genetic architecture of fruit quality traits in this wild species can facilitate and speed up future breeding efforts for introgression and de novo domestication. Therefore, in this study, we developed a biparental population of 147 progenies from V. stamineum, which were phenotyped and genotyped for quantitative trait loci (QTL) mapping. Phenotypic data for acidity [total titratable acidity {TTA} and pH] and sweetness (soluble solids content) were collected over 3 yr. Genotypic data were obtained through targeted sequencing using 6,000 probes developed for blueberry. A linkage map was crafted containing a total of 3,797 markers spanning a cumulative distance of 1,801 cM across 12 linkage groups. Composite interval mapping revealed a total of 20 significant QTL considering the 3 traits and years of evaluation. Two consistent overlapping QTL intervals across 2 yr were found for TTA and soluble solids in linkage groups 8 and 9, respectively. We also found a QTL for TTA that has been previously reported for cultivated blueberry. Low to moderate heritability was observed, indicating the complex genetic architecture of these traits. Overall, the newly developed high-density genetic map provides a valuable resource for trait mapping efforts in this species, and the QTL identified for fruit quality can guide future molecular breeding strategies.