Three experiments are described investigating the effects of propagation medium, applied auxin (IBA) concentration and leaf area on the rooting of leafy stem cuttings of Irvingia gabonensis, a West African fruit tree species. Cuttings were taken from seedlings or coppice shoots from selected trees in a forest reserve, and inserted in a low technology non-mist propagation system in Cameroon. The three experiments tested respectively: (i) six propagation media, namely sawdust (SD), fine sand (FS), medium sand (MS), gravel (G), and 50:50 mixtures of G:SD and MS:SD; (ii) five IBA concentrations, namely 0, 8, 40, 200 and 250 mu g IBA dissolved in 10 mu l of alcohol; and (iii) five leaf area treatments, namely 0, 12.5, 25, 50 and 80 cm(2), obtained using paper templates, The overall effect of propagation medium on final rooting percentage was highly significant (P < 0.001, ANOVA), highest values being recorded in FS and SD. Number of roots per rooted cutting also differed markedly between treatments, mean values ranging from 1.8-7.8 in G and SD respectively. In contrast, IBA had no significant effect on final rooting percentage or root number, although root development was more rapid in the 200 and 250 mu g treatments. Leaf area had a pronounced effect on rooting percentage (P < 0.001, ANOVA), with highest values recorded in the 80 cm(2) treatment, but relatively little effect on root number. Defoliated cuttings completely failed to root. The results suggest that for vegetative propagation of I. gabonensis, a cutting leaf area of at least 80 cm(2) and an organic medium such as sawdust should be used. The application of IBA would appear to be unnecessary for the successful propagation of this species.
