Effect of 2,4-Dichlorophenoxyacetic Acid on Callus Induction from Eurycoma Longifolia Leaves

Abstract

Eurycoma longifolia Jack (Simaroubaceae), known as Tongkat Ali, is a slow-growing Southeast Asian medicinal tree whose root quassinoids are of pharmacological interest. Pressure on wild populations has increased demand for in vitro propagation. This study determined the optimum 2,4-dichlorophenoxyacetic acid (2,4-D) concentration for callus induction from juvenile leaf explants of E. longifolia and evaluated proliferation during the first subculture cycle. Leaf segments and primary callus were cultured on Murashige and Skoog (MS) medium with six concentrations of 2,4-D (0 to 3.0 mg/L), in a completely randomised design with 10 replicate vessels per treatment. Hormone concentration significantly affected callus induction, fresh weight, and volume, but not dry weight. The hormone-free control produced no callus. The best response occurred at 1.0 mg/L 2,4-D, giving the highest induction (88.65%), fresh weight (2.55 g) and volume (2.64 cm³); dry matter content ranged from 4.05 to 9.18%. During subculture, this concentration remained optimal (47.15% proliferation, 1.38 g fresh weight, 1.02 g dry weight), though biomass was lower than in primary culture. Colour-quality scores were highest at 1.0 mg/L and declined at 2.5-3.0 mg/L, coinciding with visible browning. These results identify 1.0 mg/L 2,4-D as the most effective concentration for callus induction, proliferation, and visual quality.