Linking vegetative growth, reproduction and irregular bearing in the mango tree
Résumé
Irregular bearing is a major agronomic issue with economic consequences for many temperate and tropical fruit species. In particular, the mango tree, characterized by terminal flowering, is prone to irregular bearing, with a clear cultivar effect. Mango trees within a monoclonal orchard exhibit contrasting patterns of bearing, suggesting that, for a given cultivar, irregularity is triggered and/or maintained by endogenous architectural and physiological factors and not only by environmental factors. In several species, architectural traits of shoots can affect flowering. In this paper we summarize and discuss the results obtained in different studies on the reciprocal interactions between vegetative development and flowering and fruiting at different scales in the mango tree, namely the terminal growth unit, the scaffold branch and the whole tree. The topology, morphology and phenology of the mango terminal growth units affect their probability of flowering and fruiting, indicating that structural and temporal vegetative traits are clearly involved in reproduction. Conversely, the reproductive fate of a terminal growth unit affects the occurrence, intensity and phenology of its subsequent vegetative growth, which represents the potential flowering points for the following cycle. These results show that, at the mango growth unit scale, irregular bearing results from the effects of the flowering and fruiting behavior during a cycle on the reproductive behavior during the following cycle, these effects being partly mediated by vegetative growth occurring between the two reproductive events. We discuss the three following points: what are the physiological mechanisms underlying these relationships at the growth unit scale? what happens at larger scales, i.e., at the scaffold branch and the whole tree scales? and what could be the effects of climate change and cultivation practices on these relationships?