Effect of age, clone heads, ramet position and IBA treatment on the rooting of Argan tree (Argania spinosa L. Skeels) cuttings
The vegetative propagation of the Argan tree by cuttings was carried out in a glazed enclosure whose relative humidity and average temperature were 80 % and 25°C respectively. The first trial involved herbaceous cuttings taken from clone heads selected on the basis of productivity, vigor and ability to produce cuttings at different levels (heights) of the tree. Three factors were taken into account: the age of the root-stock, the branch position on the tree and the treatment with indol-butyric acid (IBA), a rooting hormone whose concentrations were 1000 and 2000 ppm compared to a control treated with distilled water. A second trial was conducted to control the overall conditions for cuttings rooting such as light, relative air humidity and substrate temperature, as well as the type of the cuttings: herbaceous, semi-woody and woody. The overall rooting rate was improved by four folds between de first and the second trial. It increased from 25 % under uncontrolled conditions to 100 % under controlled conditions in some clones. Young trees showed the greatest ability to root. Variance analysis showed a highly significant effect of clone head and branch position on rooting, dry weight and average length of cuttings. On the other hand, no significant effect was observed for auxin treatment on these variables. The best result (100 % rooting) was obtained for apical and median cuttings of sprouts of young trees under controlled conditions. Tree age has a highly significant effect on root quality since cuttings from young trees showed superior dry weight and root length. The comparative study of the root system produced by cuttings with that of seedlings showed that seedlings are characterized by a well-developed taproot while cuttings develop a cluster of cells that give rise to several orthotropic roots.
Key words: Argan tree, cuttings, age of root-stock, branch position, IBA, rooting