1. College of Agriculture, Tamagawa University, 6-1-1 Tamagawa-gakuen, Machida, Tokyo 194-8610, Japan
2. Fruit Tree Research Division, Nagasaki Agricultural and Forestry Technical Development Center, Onibashi, Omura, Nagasaki 856‑0021, Japan
3. Graduate School of Agriculture, Tamagawa University, Machida, Tokyo 194‑8610, Japan
4. Agriculture and Horticulture Research Division, Nagasaki Agricultural and Forestry Technical Development Center, Aino, Unzen, Nagasaki 854‑0302, Japan