The basal 1/2 MS medium was fortified with 2% sucrose, 100 mg l−1 myo-inositol and was solidified with 0.7% (w/v) agar. The pH was adjusted to 5.7 ± 0.2 either with 0.1 N NaOH or HCl prior to autoclaving at 120 °C and 105 kPa for 15 min. All cultures were aseptically maintained at 25 ± 2 °C under a 16/8 h (light/dark) photoperiod with a light intensity of 40 μmol m−2 s−1 by white fluorescent light.