Management of cytokinin–auxin interactions for in vitro shoot proliferation of Althaea officinalis L.: a valuable medicinal plant

Abstract

An effective, rapid and improved protocol for in vitro regeneration has been established for Althaea officinalis using nodal explants, excised from 4-week-old aseptic seedlings. Different cytokinins and auxins, alone or in combination were investigated with respect to shoot induction and development. Of the three cytokinins, 6-benzyladenine (BA), Kinetin (Kn) and 2-isopentenyl adenine (2-iP) tested as supplement to Murashige and Skoog (MS) medium, BA proved to be the most effective for induction and proliferation of shoots from nodal explants. Proliferation capacity of the induced explants was differentially influenced by a combination of cytokinins [6-benzyladenine (BA), Kinetin (Kn) and 2-isopentenyl adenine (2-iP)] and auxin [indole-3-butyric acid (IBA), indole-3-acetic acid (IAA), α-naphthalene acetic acid (NAA)]. The optimum response was observed with (7.5 μM) BA and (0.5 μM) NAA, which induced shoot regeneration in 95 % of the cultured nodal explants, with an average of 26 shoots per explant. High frequency of rooting (89 %) was obtained when shoot were transferred to ½ MS medium supplemented with (20 μM) IBA. In addition, a histological study was undertaken to better understand the origin of the regenerated shoot buds.