Analysis of the MdMYB1 gene sequence and development of new molecular markers related to apple skin color and fruit-bearing traits.

MdMYB1, a key transcription factor determining apple skin color, coordinately regulates genes in the anthocyanin pathway. In this study, we analyzed the MdMYB1 gene and its relationship to apple skin color and fruit-bearing traits to better understand this gene and its application to apple breeding. A previously reported MdMYB1 dCAPS marker failed to identify alleles of the MdMYB1 gene in 'Fuji', a very important apple cultivar. In this study, we revealed that the polymorphic site related to the MdMYB1 dCAPS marker is heterozygous in 'Fuji'. In addition, two new polymorphic sites related to apple skin color were identified in the MdMYB1 gene, with two new molecular markers accordingly developed. Testing of these markers in 'Fuji' and its progeny revealed that they could predict apple skin color and identify alleles of the MdMYB1 gene in this cultivar. Most interestingly, the allele MdMYB1-2 in 'Gala' apple and its hybrid plants was found to be related to the fruit-bearing trait, and the molecular marker Mb2 was able to identify the MdMYB1-2 allele. Our study is apparently the first to report a relationship between the MdMYB1 allele and the fruit-bearing trait in apple. More work is needed to determine whether and how the MdMYB1 gene or a gene linked to the MdMYB1-2 allele influences the flowering trait in perennial apple trees, and whether flowering in other plants is influenced by related genes.