High-density genetic map and QTL analysis of soluble solid content, maturity date, and mealiness in peach using genotyping by sequencing

Peach (Prunus persica) is one of the most important temperate fruit trees in the world, based on its production and cultivated area. Consumer acceptance is the principal objective of multiple breeding programs and it is dependent on many factors. Among these factors, an important role is played by the soluble solids content (SSC) and the postharvest performance represented by mealiness (M) susceptibility as a chilling injury disorder. Additionally, a major maturity date (MD) QTL has been reported to have a pleiotropic effect on both M and SSC. The aim of this work was QTL identification of SSC, MD, and M and to identify adequate candidate genes that are linked to regulation of these traits. The analysis was performed by evaluation of fruit quality traits during three consecutive seasons in an F1 progeny of 194 siblings, which were obtained from the intraspecific cross between the yellow-flesh peach "O'Henry" and the white-flesh nectarine NR-053. The main result was the construction of a genetic linkage map with 499 markers (486 SNPs, 11 SSRs, and two morphological markers) spanning 717.6 cM, with an average distance between markers of 1.5 cM/cluster. The analysis allowed the identification of consistent QTLs for SSC and M in the linkage group LG5 and for MD in LG1, LG2, LG5, and LG6. A large number of genes were annotated in QTL intervals, which was reduced by selecting the genes with at least one SNP, which caused an amino acid variation. For SSC, the data identified four transcription factors, one gene involved directly with the sugar accumulation process, and one cell wall remodeling-related gene. For MD, 23 cell wall-related genes, three jasmonic acid-linked genes, eight transcription factors, and one ripening-related gene were identified. Finally, only one cell wall gene was identified that was associated with M. In conclusion, these results improve our understanding of the genetic control of fruit quality traits with commercial relevance in P. persica and specifically in the O x N mapping population.