Micropropagation of a West African wild grape (<i>Lannea microcarpa</i>)

Abstract

The propagation of Lannea microcarpa (an African wild grape) by seeds causes considerable variation in the offspring, making very difficult the selection, and multiplication of superior genotypes of interest. The species is also very difficult to propagate using conventional asexual technique. Therefore, micro cutting explants of young shoots from seedlings of Lannea microcarpa were grown in vitro on semi-solid Woody Plant Medium (WPM) supplemented for each experiment with three cytokinins at seven different concentrations for shoot formation and development. The cytokinins tested were 2iP (2-isopentenyladenine), TDZ (Thidiazuron), Zea (Zeatin) plus 0.05 µM IAA in the medium. Two subcultures were performed at 35 days interval after the initial in vitro culture establishment. Shoot development occurred primarily from axillaries buds formation that was greatest on a medium containing 56 µM of 2iP (plus 0.05µM IAA), with an average number of 4.5 ± 0.3 shoots per single node cutting and an average length of 4.7 ± 0.7 cm. After removal from culture, the shoots were induced rooting using IAA (Indole-3-Acetic Acid) and IBA (1H-indole-3-butanoic acid) at seven different concentrations. Shoots rooted in response to treatment with auxins (IBA and IAA) in the WPM medium and also in talc. The WPM medium produced an average number of 7 ± 0.5 roots per cutting at 32 µM IBA and with nearly 4.5 ± 0.7 cm in length. But the 1.5% of IBA in talc gave a better result with a higher number of 7.5 ± 0.4 roots per cutting with 5.5 ± 0.6 cm in length. The objective of this study is to develop a reproducible protocol for the rapid propagation of Lannea microcarpa in a semi-solid WPM medium supplemented with various concentrations of hormones.

Keywords: In vitro propagation, Sahelean tree, Cytokinins, auxins.