Melatonin and γ-Aminobutyric Acid (GABA) Applied as Pre- or Post-harvest Treatments Affect Vegetable and Fruit Quality Properties and Antioxidant Systems

Dear Colleagues,

γ-Aminobutyric acid (GABA) is a non-protein amino acid composed of four carbons that occurs naturally in both plants and animals. In higher plants, GABA is synthesized from glutamate by the enzyme glutamate decarboxylase and metabolized through the GABA shunt pathway in two consecutive steps: first, oxidation to α-ketoglutarate; second, to succinate to enter the tricarboxylic acid cycle (TCA). Melatonin is synthesised from tryptophan through two different pathways involving the intermediates N-acetyl serotonin and 5-methoxy-tryptamine. Both melatonin and GABA are found in small concentrations in many plant sources, including fruits, vegetables, and cereals, and have many effects on plant development, including the induction of plant resistance to abiotic and biotic stresses through redox balance, osmoprotection and osmotic adjustment effects, among others. In addition, melatonin or GABA pre- or postharvest treatments delay the senescence of horticultural commodities and increase fruit chilling tolerance, leading to fruit quality maintenance during cold storage. In fact, it has been reported that MT treatment effects involve the accumulation of endogenous GABA through the GABA shunt. The present Special Issue will be focused on the effects of GABA or melatonin treatments, applied as post- or pre-harvest treatments, on fruit and vegetable quality traits, with special emphasis on antioxidant systems, both enzymatic and non-enzymatic, and the mechanisms involved in these effects.

Prof. Dr. María Serrano
Prof. Dr. Daniel Valero
Guest Editors

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• anthocyanins
• phenolics
• firmness
• colour
• sugars
• organic acids
• taste
• antioxidant enzymes