| Summary: | In Africa and Asia, members of the genus <i>Brachystelma</i> are well-known for their diverse uses, especially their medicinal and nutritional values. However, the use of many <i>Brachystelma</i> species as a valuable resource is generally accompanied by the concern of over-exploitation attributed to their slow growth and general small size. The aim of the current study was to establish efficient micropropagation protocols for three <i>Brachystelma</i> species, namely <i>Brachystelma ngomense</i> (endangered), <i>Brachystelma pulchellum</i> (vulnerable) and <i>Brachystelma pygmaeum</i> (least concern), as a means of ensuring their conservation and survival. This was achieved using nodal segments (~10 mm in length) as the source of explants in the presence of different concentrations of three cytokinins (CK) namely <i>N</i><sup>6</sup>-benzyladenine (BA), isopentenyladenine (iP) and <i>meta</i>-topolin riboside (<i>m</i>TR), over a period of 6 weeks. The highest (25 µM) concentration of cytokinin treatments typically resulted in significantly higher shoot proliferation. However, each species differed in its response to specific CK: the optimal concentrations were 25 µM <i>m</i>TR, 25 µM iP and 25 µM BA for <i>Brachystelma ngomense</i>, <i>Brachystelma pulchellum</i> and <i>Brachystelma pygmaeum</i>, respectively. During the in vitro propagation, both <i>Brachystelma ngomense</i> and <i>Brachystelma pygmaeum</i> rooted poorly while regenerated <i>Brachystelma pulchellum</i> generally lacked roots regardless of the CK treatments. Following pulsing (dipping) treatment of in vitro-regenerated shoots with indole-3-butyric acid (IBA), acclimatization of all three <i>Brachystelma</i> species remained extremely limited due to poor rooting ex vitro. To the best of our knowledge, the current protocols provide the first successful report for these <i>Brachystelma</i> species. However, further research remains essential to enhance the efficiency of the devised protocol.
|