(R&M Chem- icals, UK) and 7 g/L gelrite agar (Duchefa, Netherland) and the pH was adjusted to be within 5.6–5.8 by using 1 mol/L HCl and NaOH after the addition of plant hormones. The media were autoclaved at 121 C under the pressure of 1.06 kg/cm2 for 15 min.