UC Riverside

Avocado (Persea americana, Mill.) fruit production continues to be an expanding business worldwide. Larger amounts of quality fruit are needed to satisfy the demand but there seems to be an embedded tradeoff: after trees bear many fruits, they seem bound to produce too little the following season and vice versa. These yield fluctuations are horticulturally known as “alternate bearing” and is traditionally considered to be a consequence of negative perturbations rising from fruits themselves. But, is it? Are we approaching the issue with models that need fruits to be actively detrimental to the tree? Now that we are utilizing molecular tools in avocado research: do we properly distinguish the phenotypes when we sample? Future research could experience difficulties due to those scenarios and hence this investigation explored which were the actual vegetative and reproductive growth phenotypes between fruiting and a non-fruiting shoots as, due to “alternate bearing”, they were expected to be divergent. Typically, fruiting shoots grow one vegetative flush and, by the end of the first growth season, do not release lateral branches. At their succeeding season, fruiting shoots display reduced release of axillary buds and, if they bloom, a low flowering complexity. Conversely, non-fruiting shoot initiate more consecutive vegetative flushes, undergo lateral branching and during the succeeding season release more axillary buds displaying a gradient of acropetally increasing reproductive growth presence and complexity. Although comprehensive and resilient in different production areas of the world, these divergent phenotypes can be practically swapped by sunlight exposure within the canopy environment. Avocado trees seem so dynamically responsive to sunlight that it can render fruit presence phenotypically unimportant and, with that, new working models for avocado “alternate bearing” need to consider contextual and dynamic research approaches. Phenotypically complying models that can accommodate to sunlight exposure may be achieved by assigning fruits with a more passive role of a strong sink organ that is necessary for the life cycle of the avocado tree, certainly not detrimental or powerful enough to be the single and ultimate explanation of the “alternate bearing” phenomenon.