Sweet bell pepper, due to its tropical origin, is highly susceptible to chilling injury (CI), fungal decay, and quality deterioration during cold storage. Recently, the use of environmentally friendly and low-risk compounds has emerged as a promising approach to mitigate postharvest fungal decay and CI. This study aimed to evaluate the effects of preharvest application of β-aminobutyric acid (BABA) on the control of Alternaria alternata (Fr.) Keissl fungal decay (AFD) and CI in ‘California Wonder’pepper fruit during storage. For this purpose, an experiment was conducted from 2022 to 2024, with preharvest sprays of BABA at concentrations of 0, 5, 10, 15, and 20 mM. Treated fruit were stored at 3 °C with 80–85 % relative humidity and assessed for various quality attributes at harvest (0 d) and after 10, 20, and 30 d of storage. The results showed that CI severity and AFD increased over time, while fruit quality declined. However, BABA treatments maintained postharvest fruit quality. Notably, the 15 mM BABA treatment extended shelf life by 38 % (10 d) and reduced CI and AFD by 51 % and 62 %, respectively, compared to the control. Throughout storage, the 15 mM BABA treatment reduced weight loss, electrolyte leakage, hydrogen peroxide, proline, malondialdehyde, phospholipase D, lipoxygenase, glutamate decarboxylase activity, and γ-aminobutyric acid (GABA) content. Moreover, this treatment preserved fruit firmness, titratable acidity, total soluble solids, ascorbic acid, total protein content, and the activities of antioxidant enzymes, including ascorbate peroxidase, guaiacol peroxidase, catalase, superoxide dismutase, and GABA transaminase. These findings demonstrate that preharvest BABA application enhances both the quantitative and qualitative attributes of sweet bell pepper fruit, thereby extending shelf life and reducing losses caused by CI and AFD. The improved antioxidant defense, regulation of GABA biosynthesis, and the potential antimicrobial action of BABA through cell wall fortification are likely key mechanisms contributing to its effectiveness.
