Color development of 4 Apple Cultivars Grown in the Southwest of Japan, with Special Reference to Fruit Bagging

Abstract

Seasonal changes in anthocyanin and total phenol content and PAL activity in the fruit skin, and in ethylene production by whole fruit, were determined with 4 apple cultivars grown in the southwest of Japan; ‘Fuji’, ‘Jonathan’, ‘Starking Delicious’ (SD), and ‘Golden Delicious’ (GD). Also the effect bagging of fruit, a Japanese conventional practice to improve fruit appearance, on these characterisitics was investigated.
In all cultivars, higher PAL activity in the skin was observed at earlier stages of fruit development, followed by a rapid decline toward the preclimacteric to a considerably lower level. Then it gradually increased again with the onset of coloration and ethylene production. ‘Jonathan’ and ‘SD’ developed more anthocyanin and higher PAL activity than ‘Fuji’.
In spite of no anthocyanin development, ‘GD’ also showed higher PAL activity. Good color development was observed in red cultivars by fruit bagging, followed by removal of the bag. However, anthocyanin content at harvest was almost same in fruits with or without bagging.
Shading the fruit by UV cut-off film following removal of paper bags considerably inhibited anthocyanin formation in red cultivars. Bagging did not show any consistent effect on ethylene production.When ‘SD’ fruit was kept bagged with paper bags or shaded by UV cut-off film after removal of paper bags, both anthocyanin accumulation and PAL activity were inhibited or reduced, suggesting their positive relationship in this cultivar. In other cultivars, however, a considerably high level of PAL was found with bagged fruits in spite of coloration.
In conclusion, a higher level of PAL activity in apple skin during ripening seems to be essential to the development of anthocyanin, but it does not always result in good color development.