Effect of Water Regimen on Fruit Growth, Metabolomic Profile, and Postharvest Quality of ‘Hass’ Avocados

Preharvest climatic conditions and irrigation management are decisive determinants of avocado postharvest performance. Avocado trees are highly susceptible to the water regimen, conditions that disrupt carbon assimilation, mineral nutrient uptake, and biomass partitioning. This study evaluated the effects of deficit irrigation imposed during early stages of fruit growth, coinciding with active cell division, on fruit development and postharvest quality of ‘Hass’ avocado. Deficit and excess irrigation induced physiological stress, reducing stem water potential (≈−1 MPa) and altering photochemical efficiency, while FV/FM remained unaffected. Fruit growth was strongly affected, with weight reductions of up to 26% during development and 22% at harvest under severe deficit, resulting in fruits becoming more yellowish-green. In contrast, excessive irrigation promoted larger fruit with darker green skin, with delayed maturation. Metabolomic revealed that the fruit developmental stage was the main driver of metabolic variation, while irrigation effects were minor and stage-dependent, limited to osmotic-related metabolites such as GABA. These findings indicate that early-season water imbalances primarily affect fruit growth through changes in water relations rather than metabolic reprogramming, highlighting the importance of precise irrigation management during critical developmental stages. Fine-tuning water supply during early developmental stages is a strategic tool for optimizing fruit size and postharvest quality in avocado.