VEGETATIVE PROPAGATION OF IRVINGIA-GABONENSIS, A WEST-AFRICAN FRUIT TREE

Three experiments are described investigating the effects of propagati on medium, applied auxin (IBA) concentration and leaf area on the root ing of leafy stem cuttings of Irvingia gabonensis, a West African frui t tree species. Cuttings were taken from seedlings or coppice shoots f rom selected trees in a forest reserve, and inserted in a low technolo gy non-mist propagation system in Cameroon. The three experiments test ed respectively: (i) six propagation media, namely sawdust (SD), fine sand (FS), medium sand (MS), gravel (G), and 50:50 mixtures of G:SD an d 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 treat ments, namely 0, 12.5, 25, 50 and 80 cm(2), obtained using paper templ ates, The overall effect of propagation medium on final rooting percen tage was highly significant (P < 0.001, ANOVA), highest values being r ecorded 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 an d 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 r ecorded in the 80 cm(2) treatment, but relatively little effect on roo t number. Defoliated cuttings completely failed to root. The results s uggest that for vegetative propagation of I. gabonensis, a cutting lea f area of at least 80 cm(2) and an organic medium such as sawdust shou ld be used. The application of IBA would appear to be unnecessary for the successful propagation of this species.