Harvest date in apple (Malus x domestica) is an important trait for breeders making crossing and selection decisions. Early harvest date has been associated with lower hedonic ratings for fruit quality traits and decreased storability due to softening compared to apples that mature later in the season. An objective for breeders and producers is to have genotypes with early season ripening and improved texture and storage traits that could replace less desirable cultivars. Conversely, in production regions with short growing seasons, late season cultivars may never ripen fully before freezing and cannot be harvested. The development of molecular markers that inform plant breeders on harvest date would be useful in selecting parents for cultivar development and for screening seedlings as part of marker assisted breeding (MAB). Selected seedlings and advanced breeding lines could also be targeted to testing locations with appropriate season lengths. A pedigree-linked population was investigated for harvest date quantitative trait loci (QTL) for 2011 and 2012. Growing degree day accumulation (base 4.4 °C) at harvest was used as a proxy for calendar date in order to compare years and to normalize data for ancestors grown at other locations as part of the RosBREED project. The analyses evidenced QTL on linkage groups 3, 4, 7, 8, 11, 14, and 15. The QTL on LG 3 co-localized with a QTL for sensory firmness and harvest date from previous reports in apple. This study will provide marker-trait-loci associations through the identification of functional SNP haplotypes which span the QTLs and can be utilized in MAB.
