Differential responses to isoprenoid, N 6-substituted aromatic cytokinins and indole-3-butyric acid in direct plant regeneration of Eriocephalus africanus

Abstract

Eriocephalus africanus is a medicinal and aromatic plant species that is part of South Africa’s remarkable diversity. As a result of illegal and over-harvesting, most plant communities have become unsustainable and as such, effective and efficient conservation strategies have to be implemented. In the present study, an isoprenoid cytokinin (CK): isopentenyladenine (iP) and four aromatic CKs namely benzyladenine (BA), meta-topolin (mT), meta-topolin riboside (mTR) and 6-(3-hydroxybenzylamino)-9-(tetrahydropyran-2-yl)purine (mTTHP) at 1, 5 or 10 µM were evaluated for in vitro plant regeneration in E. africanus. Different concentrations of indole-3-butyric acid (IBA) were also evaluated for shoot and root organogenesis. The highest number of shoots was produced by mT (1 and 5 µM) treatment, longest shoots were stimulated by iP (1 µM) and the highest fresh mass was obtained in BA (5 and 10 µM), mT (5 and 10 µM) and mTTHP (5 µM)-treated plants. During acclimatization, all the in vitro plants obtained from the lowest concentration of CKs survived and 1 µM iP regenerants recorded a 100% survival rate. For the rooting experiment, more vigorous adventitious roots were observed in the 1 µM IBA treatment. All IBA treatments had 100% survival rate after 6 weeks of acclimatization. Overall, the concentration and type of plant growth regulators had a remarkable influence on the growth and development of in vitro-derived E. africanus.