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Lemon fruit (Citrus limon (L.) Burm.) is highly appreciated by consumers due to its antioxidant properties and health benefits. However, its shelf life can be limited by various factors, reducing the economy, and thereafter, new strategies to maintain the quality of lemons are necessary. Melatonin is a derivative of tryptamine, which is ubiquitously found in plants and has a wide range of functions regulating numerous physiological processes in plants. During two consecutive harvests, we evaluated the effect of preharvest treatments with melatonin on crop yield and on quality and functional properties of fruit of lemon cv. Verna at harvest and weekly after storage up to 28 days at 2 and 10 °C plus 2 days at 20 °C. Melatonin was applied as foliar spray treatments at dosages of 0.1, 0.3, and 0.5 mM and at three different stages of fruit development. The results showed that melatonin treatment had a positive impact on crop yield as well as in fruit quality parameters, such as firmness, content of bioactive compounds, and antioxidant activity, especially for a 0.5 mM dose. Taking all these effects into account, the application of melatonin along the growth cycle of fruit development could be considered a non-contaminant and eco-friendly tool for improving crop yield and quality of 'Verna' lemons at harvest and during postharvest storage. [ABSTRACT FROM AUTHOR]

γ-Aminobutyric acid (GABA) plays important roles in plant development, including the maintenance of fruit quality when applied as postharvest treatment. However, little information is available about the effects of preharvest GABA treatments. Thus, GABA (10, 50 and 100 mM) was applied as foliar spray at key points of fruit development in three sweet cherry cultivars and over two years. The results show that quality parameters, such as total soluble solid content, titratable acidity and firmness were higher in the fruit from GABA-treated trees than in the controls, either at harvest or during four weeks of cold storage. In addition, the total phenolic and total and individual anthocyanin concentrations were also enhanced by GABA treatments and the fruit color was improved. The activities of the antioxidant enzymes catalase, ascorbate peroxidase and peroxidase were also enhanced by the GABA treatments. The most effective concentration was 50 mM, which led to extending the storage period of sweet cherries with high quality traits to up to four weeks, while for the controls this was two weeks. Thus, GABA treatment had a clear effect on delaying the postharvest ripening and senescence processes in sweet cherries, with an additional effect on enhancing the content of bioactive compounds, such as phenolics and anthocyanins, with antioxidant properties and health benefits. [ABSTRACT FROM AUTHOR]

γ-aminobutyric acid (GABA) is a naturally occurring plant compound that acts as a signalling agent during stress conditions, mainly due to unstable events, although sometimes the endogenous content does not reach sufficient levels. Thus, the main aim of this study was to apply GABA preharvest treatments in lemon and to study its effects on quality attributes at harvest and during postharvest storage. GABA was applied as foliar spray at 10, 50, and 100 mM, and quality traits during 28 days of storage at two temperatures (at 2 and 10 °C) were determined. Results show that all GABA treatments had a positive effect on reducing the weight losses and fruit softening. In addition, crop yield in terms of kg tree−1 and fruit number tree−1 was improved for the first and second harvest as well as the total phenolics content and total antioxidant activity (TAA). In conclusion, GABA at 50 mM concentration was the most effective preharvest treatment, enhancing shelf life being enhanced for 14 and 7 days at 2 and 10 °C, respectively, with respect to control lemons. [ABSTRACT FROM AUTHOR]