1. Department of Applied Biology and Chemistry, Faculty of Applied Bio‐Science, Tokyo University of Agriculture, Setagaya‐ku, Tokyo 156–8502, Japan;
2. Forestry and Forest Products Research Institute, PO Box 16, Tsukuba Norin Kenkyu Danchinai, Ibaraki 305‐8687, Japan;
3. Department of Biological Production, Akita Prefectural University, Akita City, Akita 010‐0195, Japan