Comparison of Sugar Accumulation Characteristics in ‘Haruka’ and ‘Fuji’ Apple Fruits

We investigated changes in the sugar contents of leaves, pedicels, and fruits, and in the photosynthetic rates and translocation of photosynthate in ‘Haruka’ apple trees, along with the effects of bagging on these characteristics. After July, the total sugar contents were higher in ‘Haruka’ than in ‘Fuji’ fruits. ‘Haruka’ demonstrated higher fructose and sucrose contents in fruits than ‘Fuji’ did. ‘Haruka’ those of leaves showed higher total sugar and sorbitol contents compared to ‘Fuji’ in August and September. Total sugar and sorbitol contents in pedicels were also higher in ‘Haruka’ than in ‘Fuji’ during the fruit growing period. The total sugar contents became lower in ‘Haruka’ harvested fruits only when bagged. Decreased fructose contents were responsible for decreased sugar contents in bagged ‘Haruka’ fruits. For ‘Haruka’ and ‘Fuji’, total sugar contents in leaves were not affected by bagging, but the fructose contents in pedicels were higher in bagged fruits than in non-bagged fruits. However, we could not clarify the relationship between the effects of cultivar and bagging on sugar accumulation and photosynthetic rates and the translocation of photosynthate from leaves to fruits.