Agrobacterium-medaited transformation was performed according to the method described by Horsch et al. (1985). Co-cultivation medium was MS basal salts supplemented with 1.5 mg/l indolebutyric acid (IBA), 0.5 mg/l naphtalene acetic acid (NAA), selective regeneration medium was MS with 1.5 mg/l IBA, 0.5 mg/l NAA, 200 mg/l cefotaxime, 100 mg/l kanamycin, and root-inducing medium was 1/2 MS medium containing 200 mg/l cefotaxime and 50 mg/l kanamycin