Exogenous Gibberellic Acid (GA3) Enhances Mango Fruit Quality by Regulating Resource-Related Metabolic Pathways

Efficient resource allocation during fruit expansion and ripening is critical for enhancing mango (Mangifera indica L.) productivity and fruit quality. A study was conducted to quantify the effects of foliar-applied GA3 at concentrations of 0 (control), 50 (GA50), 100 (GA100) and 200 (GA200) mg L−1, applied at 15, 25 and 35 days after full bloom, on fruit physiochemical attributes during the fruit expansion and ripening phases. In addition, metabolic profiling and pathway analysis were conducted after fruit ripening. Compared with the control, GA3 application at 50, 100, and 200 mg L−1 increased fruit length by 8, 12, and 14%, and fruit diameter by 5, 11, and 14%, respectively. The mean single-fruit weight was increased by 5–11% at physiological maturity. During the fruit expansion phase, GA3 treatment decreased starch and total acidity by up to 11% and 29%, respectively, while increasing the soluble sugar content by 21%. Furthermore, enhanced antioxidant enzyme activities (SOD, POD, and CAT), accompanied by a reduction in malondialdehyde (MDA) contents in leaves, were observed. At the ripening stage, GA3-treated fruits exhibited lower weight loss, higher firmness, more uniform color development, and reduced disease incidence, although vitamin C content and total soluble solids declined. PCA analysis identified GA100 as the optimal treatment. Metabolomics analysis revealed 287 differentially regulated metabolites between GA100 and the control. Sweet, fruity, and floral compounds were upregulated, whereas terpenoids and aldehydes were downregulated. KEGG pathway analysis indicated that GA100 modulated key resource-related metabolic pathways, including nitrogen, carbon and energy metabolism, thereby promoting efficient resource allocation toward fruit growth, quality, and aroma development. Overall, preharvest foliar application of GA3, particularly at a concentration of 100 mg L−1 (GA100), markedly improved mango fruit growth and quality but tended to simplify the aroma profiles by favoring ester production over complex terpenoid-derived notes.