The other main attribute for sweet cherry marketability is fruit quality. In this region, NAC transcription factors have been reported as candidate genes for MD in peach 15 and other Rosaceae species like apple 16. A main QTL for FD time was found on the same LG4 genomic region where the MD QTL has been identified in these species 5, 13, 14. FD time has also been investigated in Prunus, but only in apricot and peach. The same LG4 QTL has been reported in other Prunus species, including apricot ( Prunus armeniaca L.), peach ( Prunus persica L.), and plum ( Prunus salicina Lindl.) as the main MD QTL 5, 7, 10, 11, 12. In this case, LG4 QTL explained 48.4% of the variation. 9 in another segregating sweet cherry population (‘Beniyutaka’ × ‘Benikirari’). This major MD QTL was also identified by Isuzugawa et al. A large percentage of variation was explained by a QTL on LG4 (20.4%), which was associated with advancing maturity 5.4 days 7. Analysis of MD in a ‘Regina’ × ‘Lapins’ population during 3 years 7, 8 identified three stable QTLs on linkage groups (LGs) 1, 4, and 5. Quantitative trait locus (QTL) analyses have been conducted in sweet cherry to investigate the genetic control of MD 7, 8, 9 but not FD period. Thus, the investigation of FD time and MD, their relationship, and that with bloom time (BT) is of high interest for breeding for early and late maturity in sweet cherry and cultivar adaptation to different growing areas. In colder regions, late blooming may be desired to avoid damage due to spring freezes, and in warmer regions, low chilling requirement cultivars are desired to ensure flowering. Early and late blooming are also breeding objectives for market and crop adaptation 6. In apricot and peach, it has been observed that FD and MD also display broad variability and a large positive correlation 4, 5. Sweet cherry MD is related to bloom date and fruit development (FD), both of which vary between cultivars. Late-maturing cultivars are also a breeding target, as these allow extending the harvesting season 3. As early ripening cultivars generally command the highest prices 2, understanding the genetics of MD is highly relevant for breeding. Sweet cherries are mainly consumed as fresh fruit, and therefore, their market profitability is directly related to their maturity date (MD) and fruit quality 1. Sweet cherry ( Prunus avium L.) is a highly demanded fruit as it is the earliest stone fruit to ripen and because of its great consumer acceptance. Haplotypes of breeding interest on this LG4 genomic region were identified and will be useful for sweet cherry breeding from this and related plant material. NAC transcription factor genes identified on this LG4 region may be candidate genes for the regulation of these traits in sweet cherry, as previously described in syntenic regions of other Rosaceae species. These traits also showed significant positive correlation (long fruit development time associated with late maturity, high firmness, and high SSC). The major QTLs for fruit development time, maturity date, firmness, and soluble solid content were identified on the same narrow region of linkage group 4. Of these, nine are first reported in this work. Eighteen were more stable as they were detected for 2 years. Significant QTLs were detected for all the traits. Fruit development time, soluble solid content, and titratable acidity QTLs are first reported in sweet cherry in this work. QTL analyses were conducted using a multifamily approach implemented by FlexQTL ™. The six populations ( n = 411), previously genotyped with RosBREED Cherry 6 K SNP array, were phenotyped for 2 years. These populations descend from cross- and self-pollinations of local Spanish sweet cherries ‘Ambrunés’ and ‘Cristobalina’, and breed cultivars (‘Brooks’, ‘Lambert’, or ‘Vic’). Six sweet cherry populations segregating for these traits were used for QTL analyses. In this work, sweet cherry fruit development time, maturity date, and commercial fruit-quality traits (size, weight, firmness, soluble solid content, and titratable acidity) were investigated to improve the knowledge of their genetic control, and to identify alleles of breeding interest. Sweet cherry maturity date and fruit quality are relevant traits for its marketability, transport, and consumer acceptance.