The branching pattern of a tree determines the efficiency of light interception and carbon assimilation. Pruning can modify the branching pattern, because of changes in physiological and environmental conditions,and ultimately pruning can have major effects on yield. For one of the major tropical tree crops, cocoa (Theobroma cacao), very little is known about branching response to pruning.To address this knowledge gap, we performed a pruning experiment on young cocoa trees in Côte d’Ivoire.We applied five treatments: two heading treatments (the removal of the terminal apex or 66% of a primary branch) and two thinning treatments (the removal of 1 or 2 primary branches) and one unpruned control.The secondary-branching pattern of the primary branches was described by the number, position, and length of secondary branches right after pruning, and the same observations were repeated after a cycleof leaf production. The probability of branching and the length of secondary branches along a primary branch, in pruned and unpruned conditions, was analyzed using generalized mixed effect models.In unpruned conditions, the probability of secondary-branch presence was higher towards the middle of the primary branches and lower at the extremes.Secondary-branch length decreased going from the base to the tip of a primary branch. After one cycle of leaf production, new secondary branches emerged preferentially on the distal section of a primary branch,but probability of branch emergence was reduced by the presence of other secondary branches. Pruning increased the probability of branch emergence mostly towards the tip of a primary branch,with heavy heading having the strongest effect. By contrast, heavy thinning increased branch emergence also toward the base of the primary branch.Our results can be applied to improve formation pruning, as this may trigger branching in different parts of the crown, depending on the form of pruning. Our study also assists the development ofthree-dimensional tree models that could further our understanding of the impact of pruning on cocoa growth and productivity.

Date Submitted: 2023-06-20