Direct shoot regeneration from leaf explants of Digitalis lamarckii, an endemic medicinal species

Abstract

This study reports, for the first time, an efficient in vitro plant regeneration protocol for Digitalis lamarckii Ivan. (dwarf foxglove) via direct shoot organogenesis. Two sets of experiments were carried out; the first compared different concentrations of 6-benzylaminopurine (BAP), kinetin, thidiazuron (TDZ), and zeatin alone using leaf explants excised from in vitro germinated seedlings, while the second set tested the combinations of indole-3-butyric acid (IBA) with BAP, kinetin, TDZ, and zeatin for shoot multiplication from the leaf explants, which were already cultured and developed numerous shoots during the first set of experiments. For shoot regeneration (the first set of experiments), TDZ was the most effective at 1.0 mg L^{-1} concentration, producing a mean of 10.3 shoots per explant and was significantly more effective than BAP. For shoot multiplication (the second set of experiments), a combination of 0.2 mg L^{-1} IBA with 0.2 mg L^{-1} TDZ produced significantly more shoots per explant (16.5 shoots) than with BAP (11.0 shoots), zeatin (5.5 shoots), or kinetin (4.0 shoots). The regenerated shoots were readily rooted on medium containing 0.5 mg L^{-1} indole-3-acetic acid (IAA). Rooted regenerants were then transferred to the pots, where they grew well and attained maturity. The described protocol provides a simple way to regenerate plants through direct shoot organogenesis, which would be useful for a large-scale production of cardenolides, germplasm conservation, and genetic transformation studies in this medicinally important endemic species.