VEGETATIVE PROPAGATION OF THE HYBRID ×CUPRESSOCYPARIS LEYLANDII BY CUTTINGS: EFFECT OF INDOLE-3-BUTYRIC ACID AND WOUNDING

Leyland cypress is a particularly difficult-to-root hybrid and, since hybrids can only be propagated through vegetative propagation, a rooting experiment took place in Portugal (Castelo Branco), in February 2007. The aim was to study the influence of different indole-3- butyric acid (IBA) concentrations, wounding the base of the cutting and rooting duration period on the vegetative propagation of the hybrid ×Cupressocyparis leylandii (A.B. Jacks. & Dallim.) Dallim. Three different IBA concentrations were used: 3,000, 8,000 and 13,000 ppm. The data was recorded 3 and 4 months after cutting bench plantation. The parameters analyzed were: the number of rooted cuttings, the number of cuttings with callus formation and dead, the number of roots (NR) and the main mean root length (MRL) per rooted cutting. The hybrid responded significantly and positively to the IBA application, but the rooting rate, the NR and the MRL were independent of the auxin concentration. After 4 months, the highest values were obtained with wounding and 13,000 ppm of IBA, with a rooting rate of 27%, 0.17 average roots and 14.3 mm average length of the main root per rooted cutting. Those values were significantly superior to 0 and 3% of rooting, 0 and 3.33 roots per cutting and, 0 and 1 mm of length of the main root, in the control and in the wounding treatments, respectively. No differences were found in the percentage of rooted cuttings, NR and MRL, between the treatments with wounding + IBA from the treatments with only IBA application. The experiment proved that the hybrid can not root unless IBA is applied, and that the wounding does not significantly increases the number of rooted cuttings.