In vitro mass propagation of Sikkim Himalayan Rhododendron (R. dalhousiae Hook. f.) from nodal segment

Abstract: The first successful micropropagation protocol was developed for an important Sikkim Himalayan Rhododendron, R. dalhousiae Hook. f. also known as Lahare Chimal in Sikkim. In vitro raised shoot tip explants from R. dalhousiae were used to produce multiple shoots on a medium containing various concentrations of growth regulators. Among the combinations used, Murashige and Skoog (MS) medium containing 5 mg L^-1 2-isopentenyladenine (2iP) along with additives such as, 100 mg L^-1 polyvinyl pyrrolidone (PVP), 100 mg L^-1 ascorbic acid, 10 mg L^-1 citric acid was found to be best for induction of multiple shoots within 12 weeks of culture. The combination of 5 mg L^-1 2iP +1 mg L^-1 indole-3-acetic acid (IAA) resulted in further multiple shoot production than using them alone. Rooting of shoots in vitro was achieved on MS medium containing 0.2 mg L^-1 indolebutyric acid (IBA). Rooted plantlets were transferred to small polythene bags containing autoclaved fresh peat moss and soil (1:3) and maintained with a high humidity for acclimation. These in vitro-raised plants grew normally in greenhouse and natural habitat (arboretum of the Institute) without showing any morphological variation. The protocol developed from the present study could be used for large scale multiplication of R. dalhousiae in a limited time.