Vegetative propagation of Lovoa trichilioides: effects of provenance, substrate, auxins and leaf area

Abstract

Lovoa trichilioides (African walnut, dibetou or bibolo) is an important commercial timber species indigenous to West and Central Africa. However, the lack of seeds and the destruction of young seedlings by shoot-borers have hampered large-scale regeneration of this species. As vegetative propagation is an effective means of multiplying selected trees within a tree improvement programme, this study focused on the main factors affecting the rooting ability of leafy stem cuttings. When testing different rooting substrates, single-node, leafy stem cuttings rooted significantly better in coarse gravel than in a forest topsoil-gravel mixture. The application of indole-3-butyric acid (IBA) had no clear effect on mean rooting perentage, although three out of four treatments with differing concentrations of IBA gave final results that were significantly better than the control. However, 50?g IBA can be considered to be an appropriate concentration to promote their rooting. Rooting ability was also affected by the node position. Cuttings from the apical nodes rooted significantly better than those from basal nodes of the same stem. Cuttings with large leaf areas (50-200 cm2) rooted better than those with smaller trimmed leaves (60% in 9 weeks versus 0 and 37% for those with 0 and 25 cm2 respectively). The optimum of 200 cm2 is higher than that for other tropical tree species such as Triplochiton scleroxylon and Khaya ivorensis