A Major QTL Controlling Earliness of Fruit Maturity Linked to the Red leaf/Red flesh Trait in Apple cv. 'Maypole'

Abstract

Anthocyanins, which contribute red coloration to apple skin, are recognized for their antioxidant properties. Some apple cultivars also accumulate anthocyanins in fruit flesh. In this study, we analyzed the inheritance of coloration traits in fruit skin, fruit flesh, and leaves as well as their candidate gene, and searched for quantitative trait loci (QTLs) for fruit maturity linked to the red flesh trait in ‘Maypole’, using a ‘Fuji’ × ‘Maypole’ F1 population. Phenotypic segregation in the F1 population indicated that red skin, striped skin, red flesh, and red leaf traits are each controlled by separate single dominant genes and that red leaves co-segregated with red flesh. Of these, a striped skin trait derived from ‘Fuji’ corresponded to the MdMYBA genotype, known to regulate anthocyanin synthesis in fruit skin, suggesting that this genotype may be responsible for fruit skin coloring patterns. The red leaf/red flesh trait derived from ‘Maypole’ co-segregated with the MdMYB10 R6 promoter. MdMYBA and MdMYB10 were located in the same region at the bottom of linkage group (LG) 9 on the same genetic material, supporting that these genes are allelic. Analysis of the relationship between red coloration and fruit maturity revealed that fruits of red-fleshed progeny tended to mature earlier than those of white-fleshed progeny. A major QTL accounting for 35.6% of the total variance (logarithm of odds [LOD] = 8.94) was detected near the MdMYB10 locus in ‘Maypole’, indicating that the factor controlling earliness of fruit maturity is tightly linked to the red leaf/red flesh trait.