Feeding elicitors and precursors enhance colchicine accumulation in morphogenic cultures of Gloriosa superba L.

Abstract

Morphogenic cultures of Gloriosa superba were initiated on Murashige and Skoog’s medium fortified with 2 mg L⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D), 0.5 mg L⁻¹ naphthaleneacetic acid (NAA), 4% sucrose and 0.1% activated charcoal. To enhance the content of the alkaloid colchicine, morphogenic cultures were treated with different concentrations of abiotic elicitors like signalling compounds, metals, biotic elicitors, precursors and a combination of elicitors. Signalling molecules like acetyl salicylic acid (ASA) and sodium nitroprusside improved the production of colchicine. Abiotic elicitors have markedly (p ≤ 0.05 or ≤ 0.01) enhanced the colchicine content either at lower or higher concentrations. Among the metals, the highest amount of 11.67 mg of colchicine g⁻¹ dry wt was noticed at 60 mM rubidium chloride, followed by 60 mM NaCl (11.18 mg g⁻¹). Contrarily, in the presence of biotic elicitors such as Fusarium oxysporum, Alternaria solani, and Saccharomyces cerevisiae, colchicine content ranged only between 2 and 5.32 mg g⁻¹, but Bacillus subtilis repressed it. Among the aromatic amino acids, phenylalanine at 500 mg L⁻¹ influenced the highest accumulation of 19.48 mg g⁻¹ dry tissue, followed by tryptophan (12.47 mg g⁻¹), and tyrosine (9.87 mg g⁻¹), a direct precursor of colchicine biosynthesis, while intact tubers and leaves contained 4.65 and 4.16 mg of colchicine g⁻¹ dry tissue respectively. A combination of 10 µM AlCl₃ and 50 µM salicylic acid (SA) registered 17.34 mg g⁻¹ followed by 16.24 mg g⁻¹ tissue in presence of 1 µM HgCl₂ and 50 µM SA. The results suggest that the elicitor-stimulated colchicine accumulation was a stress response and can be exploited further for commercial production.