Apple breeding programs at Hirosaki University, Japan: yellow skin, red flesh, and large size

Aomori is the largest apple production area in Japan. Hirosaki University, as the only national university in this area, has been performing numerous practical experiments related to apple production. In 1981, we started an apple breeding program and have since registered three cultivars: 'Koukou', 'Kurenainoyume', and 'Hirodaimisaki'. The three main objectives of this breeding program were: (1) to produce yellow-skinned apples to reduce the grower's need to induce skin pigmentation, (2) to produce red-fleshed apples to improve consumer interest and health, and (3) to produce large apples to increase consumption as gifts. 'Koukou' and 'HFF (Hirosaki Univ. Fujisaki Farm) 63', which have yellow skin, can be produced without the need for skin pigmentation treatments such as fruit rotation and defoliation. Moreover, these cultivars contain a high sugar content, particularly sucrose, which is desired by present-day consumers. 'Kurenainoyume', 'HFF33', and 'HFF60' are red-fleshed cultivars, and, since they have no astringent taste, they can be eaten uncooked. These three cultivars are also suitable for the Asian market, because they bear fruit with fresh weights of over 350 g. 'Hirodaimisaki' and 'Maruyamafuji' are triploid, and can yield fruits of approximately 500 g. Furthermore, the sweet aroma is an attractive feature of these cultivars. At present, we are preparing a cultivation manual for growers, and we are also investigating the functional constituents of these new cultivars, such as polyphenols and anthocyanins.