Characterization of morphological traits based on a genetic linkage map in peach

Thirteen morphological characters including 9 simply inherited and 4 quantitative traits, were analyzed by using a genetic map constructed with F2 progenies from a cross between the peach cultivars 'Akame' and 'Juseitou'. The map consisted of 92 markers (9 morphological and 83 DNA markers) covering approximately 1020 cM, in which 9 linkage groups were found. Eleven SSR (simple sequence repeat) markers were mapped. Segregation of 9 qualitative traits in the F2 population fitted to the expected ratio, suggesting that these traits were controlled by single genes. Three characters relating to pigmentation showing a monogenic inheritance, i.e., flesh color around the stone, flower color (pink/pale pink) and fruit skin color, were newly identified. The fruit skin color cosegregated with the leaf color trait located on the linkage group 3. The flower color and the flesh color around the stone were located on the linkage group 4 with a recombination value of 0.13. Furthermore, several DNA markers tightly linked to flesh adhesion and 2 kinds of root-knot nematode resistance were obtained, which could be used as a reliable tool for trait selection. QTL analysis was conducted on 4 morphological traits, flowering time, maturation time, fruit dropping time, and fruit weight. Six, three, three and four QTLs were identified for these 4 traits, respectively. Among them, 12 QTLs tended to gather on the linkage groups 3 and 6, whereas no QTLs were detected on the groups 2, 4,8 and 9.