1. Institute of Microbiology and Biochemistry and Department of Agricultural Chemistry, National Taiwan University, Taipei 106, Taiwan; Institute of Botany, Academia Sinica, Nankang, Taipei 115, Taiwan; Crop Genetic Resources Laboratory, Taiwan Agricultural Research Institute, Wu-Feng, Taichung 413, Taiwan; and Asian Vegetable Research and Development Center, Shanhua, Tainan 741, Taiwan