Enhanced red pigmentation in yellow/green apples via paper bagging treatment

• The epigenetic aspects of red pigmentation focusing on DNA methylation was studied. • Differential responses of 10 yellow/green apple cultivars were explored. • Shortest paper bagging period induces epigenetic changes in ‘Mutsu’ apples. Paper bagging enhances red pigmentation in apples. We previously reported that paper bagging stimulates de novo anthocyanin synthesis in yellow/green apples ‘Mutsu’ via epigenetic changes in non-transcribed MdMYB1 alleles. In the present study, we aimed to elucidate the epigenetic aspects of red pigmentation by focusing on DNA methylation. We investigated paper bagging-induced red pigmentation in various yellow/green cultivars and determined the optimal bagging period required for enhanced red pigmentation in ‘Mutsu’. As a result, yellow/green cultivars, such as the ‘Indo’ and ‘Hirodai-Misaki’ cultivars, showed enhanced red pigmentation equivalent to that of ‘Mutsu’ cultivar after paper bagging treatment. However, it was difficult to induce red pigmentation in ‘Toki’ and ‘Kiou’ cultivars via paper bagging treatment. Paper bagging treatment for at least 119 d was sufficient to enhance the red pigmentation in ‘Mutsu,’ which was approximately 10 d shorter than the conventional cultivation period Additionally, we assessed changes in the DNA methylation status of various yellow/green cultivars with and without the paper bagging treatment. Although changes in the methylation status were observed in various yellow/green cultivars, no clear association was detected between the methylation status and red pigmentation in apples. However, the influence of demethylation on red pigmentation was observed in the 5′-upstream –168 to –45 bp region of the ‘Mutsu’ cultivar, which provides insights into the regulation mechanisms of non-transcriptional MdMYB1 alleles.