Optimizing clonal propagation for restoration of a critically threatened Andean tree: interactive effects of exogenous auxins on adventitious rooting of Cinchona glandulifera Ruiz & Pav.

Forest restoration in tropical montane ecosystems is often limited by the availability of planting material from native species. Cinchona glandulifera, a critically threatened Andean tree species, shows poor natural recruitment, which restricts its use in restoration programs. In this context, vegetative propagation may facilitate the large-scale production of planting material. This study evaluated the interactive effects of auxin type (IBA, indole-3-butyric acid; NAA, naphthaleneacetic acid; and IAA, indole-3-acetic acid) and concentration (1000, 2000, and 3000 mg L−1) on the adventitious rooting of stem cuttings under controlled nursery conditions using a subirrigation chamber system. A completely randomized factorial design (3 × 3) plus a control treatment was implemented. Rooting performance was evaluated after 60 days based on survival rate, callus formation, rooting percentage, root number, and root length. Auxin type, concentration, and their interaction significantly affected rooting responses (p < 0.05). IBA at 1000 mg L−1 produced the highest rooting percentage (82.22%), root number (10.33), and root length (5.12 mm), significantly outperforming the remaining treatments. Increasing auxin concentrations reduced rooting performance, indicating a relatively narrow optimal hormonal range. Although IAA promoted callus formation, it did not lead to functional root differentiation. These findings demonstrate that hormonal optimization can substantially improve clonal propagation efficiency in Cinchona. The propagation protocol identified here provides a practical framework for large-scale production of planting material that could support ecological restoration and conservation strategies targeting threatened Andean montane forest species.