The role of vegetative propagation in the domestication of Pausinystalia johimbe (K. Schum), a highly threatened medicinal species of West and Central Africa

Abstract

Pausinystalia johimbe (K. Schum), a tree of the Central Africa humid lowlands, is exploited for its bark to supply both export and local medicinal plant markets. The gradual destruction of the forests in which Yohimbe grows coupled with unsustainable bark harvesting methods, has resulted in local scarcity of this tree species. The study examined the amenability of P. johimbe to vegetative propagation through the rooting of leafy stem cuttings using low-cost technology polythene propagators. Using single-node leafy cuttings, three experiments were investigated in Cameroon: (i) Three propagation media (sawdust and 50:50 mixture of sand and sawdust). Initially, rooting was best in the mixed medium, but subsequently, cuttings set in the sawdust rooted better than those in sand and the mixture of sand/sawdust. However, there was no significant ( P>0.05) treatment effect on rooting percentage or on the mean number of roots per cutting. (ii) Three types of auxin at 50 μg per cutting (IAA, indole-3-acetic acid; IBA, indole-3-butyric acid and NAA, 1-naphthalene acetic acid) dissolved in 10 μl of alcohol. The control treatment received 10 μl of alcohol only. Significant differences in rooting percentage occurred after 3–4 weeks between the auxin-treated cuttings and the control. Within the same period IBA-treated cuttings rooted better than those with NAA and IBA. (iii) Four leaf areas: 0, 50, 100 and 200 cm 2. Leafy cuttings rooted better than leafless cuttings after 4–5 weeks, with 50 cm 2 leaf area being the best from week 6. Significantly higher cutting mortality ( P<0.05) occurred for leafless cuttings than for leafy cuttings. The present study clearly indicated that P. johimbe is amenable to vegetative propagation technique using juvenile single-node leafy cuttings.