1. Faculty of Agriculture and Life Science, Hirosaki University, Hirosaki 036-8561, Japan.
2. Aomori Prefectural Industrial Technology Research Center, Kuroishi 036-0522, Japan.
3. Vegetable Research Institute, Aomori Prefectural Industrial Technology Research Center, Inuotose, Rokunohe-ho, 033-0071, Japan.