Effect of plant growth regulator, light and media formulation on initiation and growth of Parkia biglobosa (Jacq.) R. Br. Ex Don callus cultures from cotyledons and mature zygotic embryos

Abstract

Cotyledons from 14-days old seedlings and mature zygotic embryos (MZE) of Parkia biglobosa were cultured on either Murashige and Skoog (1962) medium (MS) or woody plant medium (WPM) supplemented with a range of 2,4-dichlorophenoxyacetic acid (2,4-D) concentrations and incubated in either 24-hour darkness or 16-hour daylight to induce callus formation. Cotyledon explants exhibited 100% callus formation while MZE gave 66.3%. 0.55mg l^-1 2,4-D gave the highest size and weight of callus formed in both explants. WPM favored callogenesis better than did MS, and incubation in the dark promoted callus formation better than a 16-hour light regime. Analysis of variance revealed varying degrees of interaction between the tested factors on callus induction (p< 0.05). Induced calluses were sub-cultured on callus proliferation medium consisting WPM supplemented with 0.55mgl^-1 2,4-D and 0.1mg l^-1 benzylaminopurine (BAP) singly or in combination for growth. Callus growth after 3 weeks was highest (9.2mg) in media supplemented with 2,4-D only. Results of the present study are novel because callus induction in Parkia biglobosa was quantified in terms of size and weight for the first time. It was also found that WPM may be the medium of choice (rather than MS which has hitherto been used) for initiating callus P. biglobosa callus cultures using 2,4-D. These findings will enhance efficient production of P. biglobosa callus for somatic embryogenesis, callus-mediated regeneration, genetic transformation, and as raw material for secondary metabolite (thioproline) production from cell cultures.

Keywords Parkia biglobosa, Leguminosae, callus induction, woody plant medium, plant genetic resources.