PLB initiation via callus formation was clearly observed in wounded areas in the basal part of shoots after approximately 2.5 months from initial culture on half-strength MS containing 1 mg/L TDZ and 0.5 mg/L BA. The maximum percentage of explants that produced callus was 85%.This callus continued to grow actively and formed irregular and larger callus clusters 3.5 months after culture initiation (Fig. 1B).