1 Institute of Fruit Tree and Tea Science, National Agriculture and Food Research Organization, 2-1 Fujimoto, Tsukuba, Ibaraki, 305-8605, Japan. okak@affrc.go.jp.
2 Division of Apple Research, Institute of Fruit Tree and Tea Science, National Agriculture and Food Research Organization, 92-24 Nabeyashiki, Shimokuriyagawa, Morioka, Iwate, 020-0123, Japan.