Evaluation of different ratios of auxin and cytokinin for the in vitro propagation of Streptocarpus rexii Lindl.

A successful means of in vitro propagation of Streptocarpus rexii Lindl. using leaf tissue as the explants is described. Secondary explants were placed on several regeneration media supplemented with various concentrations of indole-acetic acid (IAA) and benzyladenine (BA). Optimal shoot proliferation was obtained on Murashige and Skoog basal media containing 0.1 mg/L IAA in combination with 0.5 mg/L BA. The growth of explants, as quantified by their fresh and dry weights, was significantly higher in the 1 mg/L IAA with 1 mg/L BA treatment as compared with the 0.1 mg/L IAA plus 1.0 mg/L BA. The increasing concentrations of BA reduced the percentage of explants forming roots. From regeneration media, shoots were transferred to Murashige and Skoog medium supplemented with 1 mg/L IAA for root induction. After six weeks, the rooted plantlets were removed from culture and successfully hardened off in the shade house. For the multiplication of S. rexii Lindl., the best combination was the one involving 1 mg/L IAA and BA. This treatment obtained a highest shoot count and had the highest growth rate. This could play a key role in the large scale mass propagation of this plant.    Key words: Streptocarpus rexii Lindl., initiation, rooting.