Preharvest Use of γ-Aminobutyric Acid (GABA) as an Innovative Treatment to Enhance Yield and Quality in Lemon Fruit

γ-Aminobutyric acid (GABA) occurs naturally at a low concentration in fruits, but can be increased following several stress events, playing physiological effect. Lemon trees were preharvest treated with GABA three concentrations (10, 50, and 100 mM) during two consecutive seasons (2019–2020 2020–2021). Fruit growth (diameter) crop yield (kg tree−1 number of fruits tree−1) quality traits evaluated harvest. Results showed that treatments effective increasing lemon size (a 5% higher) yield, especially for mM, the assayed seasons. Thus, was between 13 18% respect to control harvest dates. With traits, did not impact any negative effects on attributes, since total soluble solids (7–8° Brix), acidity (5–6 g g−1), fruit firmness (13–14 N mm−1) similar fruits. Therefore, applied as treatment could considered potent tool enhance