Direct shoot organogenesis from petiole and leaf discs of Withania somnifera (L.) Dunal

Abstract

An efficient and reproducible procedure is described for direct shoot regeneration using petiole and leaf explants of Withania somnifera (L.). The shoots were mainly induced from the distal end of the petiole, whereas in leaf explants, shoot regeneration was initiated from the basal part and wounded tissue. The regeneration medium that induced the highest numbers of shoots in the petiole and leaf explants was Murashige and Skoog (MS) medium supplemented with 2 mg/l N⁶-benzyladenine (BA) alone or with 0.1 mg/l a-naphthalene acetic acid (NAA). The frequency of shoot regeneration was greatly influenced by the type of explant, the carbon source, the orientation of the explant, and the basal medium used in the regeneration medium. Explants produced shoot buds and adventitious shoots within four weeks. Histological analysis of the regenerating shoots showed that the shoot buds emerged from sub epidermal parenchymal cells, with no intermediate callus formation. Plantlets were rooted on MS alone or MS containing different concentrations of 3-indolebutyric acid (IBA). The addition of 1 mg/l IBA to the medium was most effective in inducing root formation. The regenerated plantlets were acclimatized in the greenhouse and successfully transferred to the field, with a 90% survival rate. The acclimatized plants showed normal flowering and were not morphologically different from the seed-derived mother plants.

Key words: Histology, medicinal plant, plant growth regulator, plant regeneration, Withania somnifera.