Branch Diameters, Substrates, and Indole-3-Butyric Acid Effect on Cashew (Anacardium occidentale L.) Tree Propagation by Air Layering.

Ivorian cashew (Anacardium occidentale L.) orchards are essentially comprised of unselected trees of diverse origins and characterized by a very low yield per hectare. In these orchards, potentially high-yielding trees have been identified. Vegetative propagation remains the most appropriate technique for the regeneration of these trees. Air layering is the regeneration technique used for a number of wood species that are difficult to root through clonal propagation. The objective of this study was to set up a regeneration protocol using the layering technique. Specifically, we evaluated the effect of the substrates, diameter class, and indole butyric acid concentration on the rooting percentage and survival of hardened plants. For this purpose, two diameter classes 5-8 mm and 8-12 mm, four substrates (sawdust, rice chip, coco peat, and coffee integument), two concentrations of indole butyric acid (2.5 and 5 mg/L) and one control (no indole butyric acid solution). were tested. Rooting percentages of 88.09, 79.36, and 61.90 were obtained with sawdust, rice chip, and coco peat respectively. No roots were observed on the coffee integument. Diameter class 8-12 mm promoted the most significant percentage of survival (89.41%) and rooting (85.18%). The concentration of 5 mg/L favored the induction of the greatest number of roots (30.79). The specific percentage of possible survival in the field of the weaned layer was above 80%. Branches with 8-12 mm diameter treated with indole butyric acid 5 mg/L in sawdust induced was the optimum treatment combination for cashew nut layering propagation in Cote d'Ivoire. [ABSTRACT FROM AUTHOR]