Plant regeneration protocol of medicinally important Andrographis paniculata (Burm. f.) Wallich ex Nees via somatic embryogenesis

In vitro propagation of Andrographis paniculata (Burm. f.) Wallich ex Nees through somatic embryogenesis, and influence of 2,4-dichlorophenoxyacetic acid (2,4-D) on induction, maturation, and conversion of somatic embryos were investigated. The concentration of 2,4-D in callus induction medium determined the induction, efficacy of somatic embryogenesis, embryo maturation, and conversion. Friable callus initiated from leaf and internode explants grown on Murashige and Skoog (MS) medium supplemented with 2.26, 4.52, 6.78, and 9.05 muM 2,4-D started to form embryos at 135, 1059 150, and 185 d. respectively, after explant establishment. Callus initiated at 13.56 muM 2.4-D did not induce embryos even after 240 d, whereas those initiated on MS medium with 4.52 muM 2,4-D was most favorable for the formation and maturation of somatic embryos. Callus subcultured on the medium with reduced concentration of 2,4-D (2.26 muM) became embryogenic. This embryogenic callus gave rise to the highest number of embryos (mean of 312 embryos) after being transfer-red to half-strength MS basal liquid medium. The embryos were grown only up to the torpedo stage. A higher frequency of embryos developed from callus initiated on 2.26 or 4.5,2 muM 2,4-D underwent maturation compared to that initiated on higher concentrations of 2,4-D. The addition of 11.7 muM silver nitrate to half-strength MS liquid medium resulted in 71% of embryos undergoing maturation, while 83% of embryos developed into plantlets after being transferred to agar medium with 0.44 muMN(6)-benzyladenine and 1.44 muM gibberellic acid. Most plantlets (88%) survived under field conditions and were morphologically identical to the parent plant.