In vitro regeneration of Vitellaria paradoxa from shoot tip explants

Shea tree (Vitellaria paradoxa) is an essential tree crop with great potential economic value mainly because of its seed oil (shea butter) which is of high demand for manufacturing assorted products in food, cosmetic, and rubber industries. Propagation of this species is, however, hindered by relative unavailability of seed (nuts), erratic seed germination, a long vegetative phase, and latex exudation from cuttings. Thus, another method of propagation through in vitro culture is recommended for rapid multiplication of shea genotypes for large-scale cultivation. In the present study, the effects of two cytokinins, namely, 6-benzylaminopurine (BAP) and kinetin (KIN), and one auxin, namely 1-naphthaleneacetic acid (NAA), on shoot and/or root induction in vitro were assessed at various combinations/concentrations. The inclusion of these growth regulators in the culture medium significantly improved (P < 0.05) shoot/root regeneration over the controls. The highest shoot regeneration percentage (100%) was obtained on Murashige and Skoog (MS) basal medium supplemented with 2 mg * dm^-3 KIN + 0.5 mg * dm^-3 NAA or 1.5 mg * dm^-3 KIN within 7/8 days of inoculation. This medium (2 mg * dm^-3 KIN + 0.5 mg * dm^-3 NAA) showed the highest mean shoot length of 3.24 cm. Compared to KIN, BAP was more effective in inducing vigorous shoot growth. However, rooting was induced only on MS medium modified with 1 mg * dm^-3 BAP + 0.5 mg * dm^-3 NAA. These findings can serve as baseline information for in vitro, commercial scale propagation of shea tree.