Evaluation of Dormancy Characteristics and Chill Requirements of Five Apple Varieties

• Published in: Engeigaku kenkyuu Vol. 20; no. 3; pp. 323 - 331
• Main Authors: Liu, Jiayi, Komori, Sadao, Kudo, Shizuka, Kumagai, Hatsumi, Ito, Daiyu, Watanabe, Manabu
• Format: Journal Article
• Language: English; Japanese
• Published: Kyoto-City THE JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE 2021; Japan Science and Technology Agency
• Subjects: budburst; Crops; Cultivars; Cultivation; Defoliation; Dormancy; ecodormancy; endodormancy; paradormancy; Plant breeding
• ISSN: 1347-2658; 1880-3571
• DOI: 10.2503/hrj.20.323

In this study, to obtain basic information for developing new cultivation systems and shortening the term of breeding in apple, we investigated the dormancy process and chill units (CU) required to break endodormancy of ‘Fuji’, ‘Orin’, ‘Jonathan’, ‘Ralls Janet’, and ‘Rome Beauty’, which is used in a cultivation system to produce two crops per year by defoliation in Indonesia, during two or three years. As a result, the CU required to break endodormancy of ‘Rome Beauty’, ‘Ralls Janet’, and ‘Jonathan’ were higher than that of other varieties. In contrast, ‘Orin’, which tends to flower unseasonably in Japan, required low CU. The deepest period of endodormancy was longer in ‘Fuji’, ‘Jonathan’, and ‘Ralls Janet’ than in the other cultivars. The time to enter the deepest period of endodormancy and duration of the break period of endodormancy in ‘Fuji’ were the same as in ‘Ralls Janet’. The time to enter the deepest period of endodormancy was earlier and the duration of the break period of endodormancy was longer in ‘Jonathan’ than in ‘Fuji’ and ‘Ralls Janet’. The time to enter of the deepest period of endodormancy was the latest in ‘Rome Beauty’. The time to enter the deepest period of endodormancy in ‘Orin’ was comparable to that in ‘Rome Beauty’, while ‘Rome Beauty’ had more than twice the duration of the deepest period of endodormancy than ‘Orin’. These results suggest that cultivars with a low CU required to break endodormancy and short duration of the deepest period of endodormancy, such as ‘Orin’, and those which entered the deepest period of endodormancy late, such as ‘Orin’ and ‘Rome Beauty’, may be suitable for a cultivation system that produces two crops per year by defoliation.