Induction of callus and plant regeneration from shoot-tip explants of Dendrobium fimbriatum Lindl. var. oculatum Hk. f.

Abstract

Shoot-tip explants of Dendrobium fimbriatum Lindl. var. oculatum Hk. f. were cultured on modified nutrient solution of Knudson’s C, supplemented with 10% (v/v) coconut water, 0.5 mg l −1 niacin, 0.5 mg l −1 pyridoxine HCl, 0.1 mg l −1 thiamine HCl and different concentrations of N 6-benzylaminopurine (BAP) and α-naphthaleneacetic acid (NAA) in factorial combinations. After 2 weeks, the explants produced a compact mass of translucent embryogenic callus. Application of both plant growth regulators (PGRs) was essential for the induction of callus. Optimum callusing was recorded in the presence of 0.5 mg l −1 NAA and 1 mg l −1 BAP (66.7%). Following transfer to the PGR-free medium, the callus further proliferated with side-by-side regeneration of protocorm-like bodies (PLBs). These PLBs readily germinated into well-rooted plantlets in the same medium. Although the presence of exogenous PGRs was essential for the induction of callus, it was possible to maintain this callus through subculturing in the PGR-free medium for more than 2 years, without any loss of embryogenic potential. The explants that failed to respond to the callus induction media, developed elongated leafy shoots that later multiplied by axillary shoot formation. The process of axillary branching was primarily dependent on BAP, but better response was obtained in the presence of additional NAA.