Comparative QTL analysis in peach 'Earlygold' F2 and backcross progenies.

• The 'Earlygold' genome has large homozygous regions that cover 52% of its length. • Thirty-three QTLs, including 12 consistent across years, were found for 24 traits,. • A QTL hotspot on chromosome 4 affects five phenology, fruit quality and leaf traits. • Four times more QTLs were found in the F2 than in the BC1 progeny of 'Earlygold'. • Leaf anthocyanic color at senescence is determined by two independent QTLs. Based on detailed maps, DNA sequences and phenotypic data, there is a great deal of information on the genetics and genomics of 'Earlygold', a historical peach cultivar from the US. The F 2 between 'Texas' almond and 'Earlygold' peach (T × E) was used to construct the first saturated peach linkage map that later became the reference map for the Prunus genus. This population and the first backcross ('Texas' × 'Earlygold') × 'Earlygold' (T1E) yielded information on QTLs for a large number of agronomic traits, and T1E is being used as the basis for constructing a set of introgression lines of 'Texas' fragments into the 'Earlygold' background, currently in progress. This paper describes the construction of a high-density SNP map for 'Earlygold' using an F 2 population, and the QTL analysis of 24 traits. Results of maps and QTLs are compared with those from the 'Earlygold' parent of the T1E map, using the same set of markers and characters. Results show major differences between the two progenies in terms of numbers of markers mapped and the capability of detecting QTLs, with a large increase in the resolution of maps and QTLs when using the F 2 progeny compared to the T1E pseudo-testcross. In addition, we provide data on leaf senescence color, studied for the first time in peach, with two consistent QTLs located in the same position as other color-related genes and QTLs. [ABSTRACT FROM AUTHOR]