Development of an efficient in vitro regeneration system in Costus speciosus - an important herbal insulin plant

Abstract

Costus speciosus is being rapidly eliminated in its natural habitats in India and driven to a nearly threatened degree of extinction because of non-selective collection and over-exploitation. The commercial cultivation of C. speciosus is impeded owing to its poor seed viability, reduced germination rate, and weak rooting potential of vegetative cuttings. As costus could not be multiplied rapidly by conventional propagation methods, in-vitro regeneration technology was experimented with to standardize explants in addition to the combinations of plant growth regulators (PGRs) to fortify the growing media that helps to produce the enormous number of plants in a shorter duration. Several kinds of explants viz., leaves and nodes were cultured into the Murashige and Skoog (MS) medium reinforced with different combinations and doses of PGRs. A higher frequency (51.67 ± 1.7%) of the regenerated adventitious shoot was obtained from nodal segments cultured onto MS medium fortified with 0.5 mg/l Thidiazuron (TDZ) and 2.0 mg/l of 6-benzyl amino purine (BAP). TDZ in combination with BAP and Indole-3-acetic acid (IAA) exhibited a remarkable effect on shoot multiplication and elongation. Further, MS medium with 0.5 mg/l TDZ, 1.0 mg/l 2, 4-dichlorophenoxyacetic acid, and 0.5 mg/l IAA yielded a great range of callus initiation (86.66 ± 1.6%) from leaf explants. Leaf-derived callus results in the greatest shoot regeneration (56.66 ± 1.7%) response on TDZ (0.5 mg/l) and BAP (1.0 mg/l) reinforced MS medium. Elongated shoots from node and callus cultures when inoculated with the MS medium reinforced along with 1.0 mg/l of IAA and 0.5 mg/l of Indole-3-butyric acid (IBA) produced optimum rooting (88.33 ± 1.66%). The rooted young plantlets were effectively acclimatized to the environmental climate and their greenhouse survival rate was 85%.