Adventitious shoot regeneration from leaf explants of the valuable medicinal herb Plectranthus barbatus Andrews
The objective of this study was to develop an efficient protocol for adventitious shoot regeneration for Plectranthus barbatus Andrews using leaf explants. The explants were cultured on MS (Murashige and Skoog, 1962) medium containing various concentration of kinetin (KN), 6-benzylaminopurine (BAP) and thidiazuron (TDZ) (0.5 to 3.0 mg/l) or in combination with á-naphthalene acetic acid (NAA) for shoot development. The highest adventitious shoot regeneration percentage (80%) and average maximum number of 19.7 ± 2.08 shoots per explants was observed on MS medium supplemented with 1.5 mg/l KN followed by 2.0 mg/l BAP with 1.0 mg/l NAA (15.0 ± 2.20 shoots per explants). The shoots were excised and the residual explants were transferred to fresh medium where again they developed shoots. The shoots were elongated when they were cultured on half strength MS medium supplemented with 0.6 mg/l gibberellic acid (GA3) and 0.5 mg/l KN. The in vitro developed shoots produced roots when transferred to half strength MS medium augmented with 1.5 mg/l indole-3-butyric acid (IBA). The in vitro raised plantlets were successfully transferred to mixture of river sand, garden soil and saw dust (1:1:1) and was hardened in controlled environment. Hardened plantlets were transferred to soil in greenhouse.
Key words: Plectranthus barbatus, Lamiaceae, medicinal plant, leaf explants, direct organogenesis, in vitro, plant growth regulators.