Differential responses to isoprenoid, N 6-substituted aromatic cytokinins and indole-3-butyric acid in direct plant regeneration of Eriocephalus africanus
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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.
KeywordsAuxins Cytokinins Flavonoids Plant regeneration Phenolics
Gallic acid equivalents
Murashige and Skoog (1962) medium
Plant growth regulator
Photosynthetic photon flux
The University of KwaZulu-Natal and National Research Foundation, South Africa provided financial support. LP and KD thank the Ministry of Education, Youth and Sports, Czech Republic (Grant LO1204 from the National Program of Sustainability I.) for financial support. We thank Mrs Alison Young (UKZN Botanical Garden, Pietermaritzburg, South Africa) and her Staff for their assistance in maintaining the greenhouse facilities.
OMM conducted the experiments, collected and analysed data and wrote the draft paper with the help of MM and AOA. LP and KD synthesized meta-topolin, meta-topolin riboside and 6-(3-hydroxybenzylamino)-9-(tetrahydropyran-2-yl)purine. JFF and JVS provided funding and research facilities, respectively. All authors edited the paper.
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