Cultivar-Specific Differences in C6 and C7 Sugar Metabolism During Avocado Ripening: Comparative Insights from Bacon, Fuerte, and Hass

Abstract

Avocado is a unique fruit in which of seven-carbon (C7) sugars (notably D-mannoheptulose and perseitol) dominate the carbohydrate profile at harvest. Despite growing interest in sugar-mediated ripening processes, limited comparative data exist across cultivars. This work characterises the dynamic changes in non-structural carbohydrates in the mesotecarp of three commercially relevant avocado varieties—Bacon, Fuerte, and Hass—across four defined ripening stages, from unripe to overripe, with five biological replicates per stage. Using a validated hydrophilic interaction liquid chromatography–mass spectrometry (HILIC–MS) method, we quantified five key sugars and assessed their evolution through ripening. Concentrations varied among the studied samples within the following ranges: D-mannoheptulose, 0.4–49 mg/g dry weight (DW); perseitol, 0.5–23 mg/g DW; glucose, 0.8–5.3 mg/g DW; fructose, 0.6–4.5 mg/g DW; and sucrose, 0.5–3.4 mg/g DW. C7 sugar levels consistently declined, while C6 sugars increased—primarily between the intermediate and ready-to-eat stages—with distinct cultivar-specific patterns. Bacon maintained elevated C7 concentrations for a longer period; Fuerte exhibited a rapid transition from C7 to C6 sugars; and Hass displayed a more gradual and balanced shift. Multivariate analysis (partial least squares discriminant analysis, PLS-DA) effectively discriminated between cultivars at each ripening stage, confirming cultivar-specific metabolic signatures. These findings offer new insights into avocado carbohydrate metabolism, emphasising varietydependent pathways that could inform breeding strategies, optimise postharvest ripening protocols, and support the nutritional characterisation of different avocado cultivars.