Early ripening events caused by bud mutation in Beni Shogun apple

Beni Shogun (BS) apple (Malus) is the sport of Yataka, which is the sport of Fuji (FJ). Its fruits ripen about 20 days earlier and produce an earlier and larger burst of ethylene than FJ fruits. Expression levels of genes associated with ethylene synthesis (MdACS1, MdACS2, MdACS3, MdACS5A, and MdACO1-MdACO4), signal reception (MdETR2, MdETR5, and MdERS) and transduction (MdCTR, MdEIN2A, and MdEIN2B) were compared between BS and FJ fruits from 90 days after bloom (DAB) to ripening. Generally, expression of all tested genes in BS was promoted, and their expression bursts preceded those in FJ. In addition, profiles of several important quality traits were compared between BS and FJ fruits from 90 DAB to ripening. Skin coloration, fruit softening, and starch hydrolysis were affected by the BS mutation, while the loss of acidity, sugar accumulation, and average fruit weight were not regulated and partially regulated by the mutation, respectively. For aroma, some volatiles were regulated by the mutation, while others were not. Generally, esters were positively regulated by the mutation. Moreover, BS fruit exhibited a lower capacity to scavenge ROS than FJ fruit.