Abstract
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 a-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.
Highlights
Plectranthus barbatus (Lamiaceae) is an aromatic, erect herb, from a perennial rootstock distributed in tropical east Africa, West Asia, Himalaya, India and Srilanka (Matthew, 1983)
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 naphthalene acetic acid (NAA) (15.0 ± 2.20 shoots per explants)
Direct bud formation was observed from leaf explants cultured on MS medium supplemented with appropriate plant growth regulators
Summary
Plectranthus barbatus (Lamiaceae) is an aromatic, erect herb, from a perennial rootstock distributed in tropical east Africa, West Asia, Himalaya, India and Srilanka (Matthew, 1983). The leaves of the plant when burned a little and placed on the skin of the neck relieve stiffness and it is used in the treatment of bone dislocations (Baerts and Lehmann, 1989). The plant has cytotoxic and anti-tumor promoting activity and can be used in the treatment of cancer and it has been used against snakebites in India (Schanberg and Ikan, 2003). The whole plant is said to have antibacterial, anti-viral and antifungal activity (Boily and Van Puyvelde, 1986). Natural populations of P. barbatus are rapidly disappearing and it is one of the plant species in India vulnerable to extinction (Reddy et al, 2001). There are only a few reports on this plant for rapid multiplication, prompting the authors for attempting to propagate plants from leaf explants under in vitro
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