Optimization of Somatic Embryogenesis from Mature Explants of Gmelina arborea Roxb.: An Efficient In Vitro Regeneration System for Forestry Applications

Abstract

A reproducible protocol for somatic embryogenesis was developed from mature stem and leaf explants of Gmelina arborea Roxb., an economically important forestry species. Explants were cultured on Murashige and Skoog (MS) medium supplemented with varying concentrations (0.1–5.0 mg L⁻¹) of naphthaleneacetic acid (NAA) or 2,4-Dichlorophenoxyacetic acid (2,4- D), each combined with 1.0 mg L⁻¹ benzylaminopurine (BAP). No embryogenic response was observed on hormone-free medium. Auxin-supplemented media successfully induced globular somatic embryos within 35–40 days. The highest embryogenic response was obtained with 4.0 mg L⁻¹ 2,4-D + 1.0 mg L⁻¹ BAP (50.77% in stem; 46.76% in leaf explants), followed by 4.0 mg L⁻¹ NAA + 1.0 mg L⁻¹ BAP. Stem explants showed higher embryogenic competence than leaf explants. Higher auxin concentrations (>4.0 mg L⁻¹) resulted in tissue browning and reduced embryo formation. Maturation of globular embryos was achieved on MS medium containing 0.5 mg L⁻¹ NAA and kinetin (0.5– 3.0 mg L⁻¹), facilitating the sequential development of heart, torpedo and cotyledonary evolutionary stages within 25 days. The results were statistically significant (p ≤ 0.05), demonstrating the reproducibility and reliability of the protocol. This study provides an efficient somatic embryogenesis system from mature explants of G. arborea, addressing a key limitation in woody plant tissue culture and enabling large-scale clonal propagation and forestry biotechnology applications.