1. National Food Research Institute, Kannondai, Tsukuba, Ibaraki 305-8642, Japan.
2. Corresponding author. Fax: +81-29-838-7996. Phone: +81-29-838-8031. E-mail: tomokos@affrc.go.jp
3. National Agricultural Research Center for Western Region, Nishifukatsucho, Fukuyama, Hiroshima 721-8514, Japan.
4. National Agriculture and Food Research Organization, Kannondai, Tsukuba, Ibaraki 305-8517, Japan.
5. National Agricultural Research Center for Western Region, Zentsuji, Kagawa 765-8508, Japan.
6. National Institute of Crop Science, Kannondai, Tsukuba, Ibaraki 305-8518, Japan.