In vitro Propagation of Gmelina arborea Roxb. (Gamhar) Through Nodal Explants and Optimization of Sterilization and Culture Medium Protocols for Enhanced Micropropagation

Abstract

Gmelina arborea Roxb. (family Lamiaceae), commonly known as Gamhar or Khmer, is a fast-growing multipurpose timber tree of significant ecological and commercial importance in tropical and subtropical forestry. Conventional propagation methods are inadequate for large-scale, genetically uniform planting stock production. The present study describes the development of an efficient in vitro micropropagation protocol for G. arborea using nodal stem segments from semi-hardwood (green-brownish) culm-stage stock plants maintained at the State Forest Research Institute (SFRI), Jabalpur, Madhya Pradesh, India. A sequential surface sterilization regime comprising 0.1% Bavistin (Carbendazim) with Tween-20 for 10–20 min, followed by 0.1% HgCl2 for 2 min, yielded optimal decontamination with minimal phytotoxicity. Murashige and Skoog (MS) basal medium supplemented with varying concentrations of 6-Benzylaminopurine (BAP) and α-Naphthaleneacetic acid (NAA) served as the primary culture system. Culture conditions were maintained at 25 ± 2°C under a 16-hour photoperiod with white fluorescent LED illumination. Shoot bud induction, callus formation, and root initiation were evaluated over 4–8 week culture intervals. Experiments were arranged in a Completely Randomized Design (CRD), and treatment means were statistically separated by Duncan’s Multiple Range Test (DMRT) at p ≤ 0.05. Results indicate that elevated cytokinin-to-auxin ratios in MS medium significantly promoted axillary shoot proliferation, whereas high auxin concentrations favoured rhizogenesis. This protocol provides a reproducible, scalable framework for mass clonal propagation of elite G. arborea genotypes for afforestation and agroforestry programs.