Mapping QTLs for Red Skin Color in Peach

Red skin pigmentation develops through the flavonoid and anthocyanin pathways. Both genetic and environmental stimuli and their interaction (genotype x environment) control the regulation of this pathway. Sunlight induces the progression of red skin development. To study the genetic control of red skin pigmentation or blush in peach a controlled cross between two cultivars with contrasting phenotypes, ‘Zin Dai’ (~30% red skin) and ‘Crimson Lady’ (~100% red skin), was made. One F₁ hybrid, BY02p4019, with intermediate levels of blush (~65% red) was selfed to generate a segregating F₂ blush population (ZC²). The segregating population was phenotyped for blush for four years (2007, 2008, 2010, 2011) using a visual rating scale (0–5) and in 2011 using a colorimeter (L*, a*, b*). Twenty-five individuals, exhibiting a blush range from 0 (0% red) to 5 (100% red) and a normal distribution for this trait, were genotyped with an IPSC 9K peach SNP array v1. A ZC² genetic linkage map was constructed with 1,335 SNP markers, comprising 14 linkage groups. This map covered a genetic distance of ~452cM with an average marker spacing of 2.38 cM/marker and an average number of 95 markers per LG. A major QTL for blush was located on LG3, spanning ~8.94cM (LOD2), and depicting 74% blush (R²). QTL analysis for four different seasons confirms the identification of this major QTL for blush in peach, and supports its stability. In addition, three minor QTL’s were located on LG’s 4, and 7 indicating the presence of minor genes involved with blush development. Candidate genes involved in skin and flesh coloration of cherry (PavMYB10) and apple (MdMYB10) are located within the interval of the major QTL on LG3 suggesting the same genetic control for color development in the Rosaceae family. Application of standardized phenotyping and potential for using marker-assisted selection for blush in peach breeding will be discussed.