High-frequency shoot regeneration through transverse thin cell layer culture in Dendrobium Candidum Wall Ex Lindl

An efficient in vitro propagation protocol for Dendrobium candidum Wall ex Lindl. using transverse thin cell layer (tTCL) culture system was established. The frequency of shoot regeneration and the number of adventitious buds produced from the regenerated shoots significantly relied on the concentration of plant growth regulators, and the position and orientation of the explant. Murashige and Skoog (MS) medium with half-strength macronutrients and 2% sucrose, supplemented with 1.2 mg l super(-1) naphthaleneacetic acid (NAA) and 1.2 mg l super(-1) 6-benzyladenine (6-BA), was optimal for shoot regeneration. Upon this medium, the youngest explant inoculated in the upright orientation exhibited a high frequency of shoot regeneration (92%), and the highest number of adventitious buds (an average of 24.5) per explant. Rooting of shoots and adventitious buds was achieved on MS medium with half-strength macronutrients and 2% sucrose with 1.0 mg l super(-1) NAA and 1.0 mg l super(-1) indole-3-acetic acid (IAA). Plantlets were transplanted into vermiculite with a 95% survival rate in a greenhouse. Ontogenetic studies revealed that the shoots originated from the stem vascular bundles.