Salinity has emerged as a critical abiotic stress factor, significantly limiting the growth, productivity, and quality of many crop species. As the global salinization of agricultural land continues to intensify, it is crucial to explore effective mitigation strategies to sustain crop yields. γ-Aminobutyric acid (GABA), a non-protein amino acid, is present in a variety of organisms, including plants, where it fulfills diverse roles under both optimal and stress conditions. In plants, GABA is intricately involved in nitrogen metabolism, amino acid biosynthesis, and the regulation of primary and secondary metabolic pathways. Functioning through the GABA shunt, it provides the carbon skeletons and energy required for biosynthetic processes and is vital for the regulation of carbon and nitrogen balance. Under abiotic stress conditions, particularly salinity, GABA rapidly accumulates, facilitating several protective mechanisms that help plants cope with stress. These include enhancing osmotic adjustment through the accumulation of osmolytes, protecting cellular structures such as chloroplasts, and improving chlorophyll fluorescence and photosynthetic efficiency. Moreover, GABA has been shown to boost antioxidant enzyme activity, reducing oxidative stress and mitigating the damage caused by reactive oxygen species (ROS) under salinity conditions. This study explores the multifaceted role of GABA in plants under saline environments, with a focus on its physiological, biochemical, and molecular mechanisms in enhancing plant resilience. By elucidating these mechanisms, we aim to highlight the potential of GABA as a natural biostimulant to improve crop performance and sustainability in saline soils.

Background: The aim of this study was to compare and investigate the effects of 1-(3-phenyl-propyl) cyclopropene (PPCP) and melatonin (MT) as anti-ethylene agents on postharvest senescence, quality, chilling tolerance, and antioxidant metabolism in the mango fruit cv. “Keitt”. The study involved exposing the fruit to 20 μL L^− 1 PPCP or 200 μM MT, in addition to a control group of untreated fruit, before storing them at 5 ± 1 °C for 28 d. The findings revealed that the treatments with PPCP and MT were effective in reducing chilling injury and preserving fruit quality when compared to the control group. Results: The use of 20 μL L^− 1 PPCP was an effective treatment in terms of mitigating chilling injury and preserving fruit quality for 28 d. This was attributed to the decrease in metabolic activity, specifically the respiration rate and the production of ethylene, which led to the maintenance of fruit firmness and bioactive compounds, energy metabolism, and antioxidant activity, such as ascorbic acid, total flavonoids, trolox equivalent antioxidant capacity, dehydroascorbate reductase, glutathione reductase activity, ATP, and ATPase activity. The study also found that the MT treatment at 200 μM was effective in reducing chilling injury and weight loss and improving membrane stability. Additionally, it led to a decrease in malondialdehyde content and electrolyte leakage, and the maintenance of fruit quality in terms of firmness, peel and pulp colour values for mango peel and pulp total carotenoid content, as well as phenylalanine ammonia lyase and tyrosine ammonia lyase activity. These findings indicate that PPCP and MT have the potential to be efficient treatments in maintaining mango quality and minimizing post-harvest losses. Conclusion: The utilisation of treatments with 20 μL L^− 1 of PPCP or 200 μM MT was found to effectively preserve the postharvest quality parameters, in terms of bioactive compounds, energy metabolism, and antioxidant activity, of mangoes cv. “Keitt” that were stored at 5 ± 1 °C for 28 d.

Mango (Mangifera indica L.) is one of the most popular tropical fruits grown in Egypt and several other countries, making it a potential export commodity. Excessive deterioration after harvest requires various treatments to maintain fruit quality. We evaluated the treatments effects of melatonin (MT) as an anti-ethylene agent and tragacanth gum (TRG) as an edible coating individually and together (MT–TRG) before storing mangoes at 12 °C for 32 days under 85–90% relative humidity. Compared with control, all treatments were significantly effective in preserving fruit quality. Fruits treated with MT–TRG showed significantly lower decay values, respiration rates, ethylene production, and weight loss than untreated fruits. MT–TRG treatment significantly enhanced fruit quality, thereby maintaining fruit appearance, flesh color, firmness, total soluble solids and phenolic contents, and pectin methyl esterase, polyphenol oxidase, and peroxidase activities during the storage period. We propose 200 µM MT + 1% TRG as a safe postharvest treatment to reduce the deterioration of mangoes and maintain fruit quality.

Background: This study aimed to investigate the impact of protocatechuic acid (PRC) treatments on the productivity and fruit quality of 'Le-Conte' pears, with a specific focus on productivity, stone cells content, and antioxidant activity. The research spanned over three consecutive cultivating seasons, with the first season serving as a preliminary study to determine the optimal PRC concentrations and the most effective number of spray applications. During the initial season, response surface methodology (RSM) was employed to optimize PRC concentration and application frequency. PRC was evaluated at concentrations ranging from 50 to 400 ppm, with treatment frequencies of either once or twice. Considering the optimal conditions obtained from RSM results, PRC treatments at 200 ppm and 300 ppm were applied twice, and their respective effects were studied in comparison to the control in the following seasons. Results: RSM results indicated that PRC at 200 and 300 ppm, applied twice, once during full bloom and again three weeks later, yielded the most significant effects. Subsequent studies revealed that PRC treatments had a substantial impact on various aspects of fruit production and quality. Applying 300 ppm PRC once during full bloom and again three weeks later resulted in higher fruit set percentages, lower fruit abscission, and enhanced fruit yield compared to untreated trees. Additionally, the 200 ppm PRC treatment maintained physicochemical characteristics such as fruit color, increased total soluble solids (TSS), and total sugar, and maintained higher ascorbic acid content and antioxidant capacity in the fruits while reducing stone cells content and lignin. Notably, enzyme activities related to phenylpropanoid metabolism and stone cells, including phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), 4-Coumarate-CoA Ligase (4CL), cinnamyl alcohol dehydrogenase (CAD), and cinnamoyl-CoA reductase (CCR), as well as peroxidase, polyphenol oxidase, and laccase, were significantly regulated by PRC treatments. Conclusion: Overall, this study suggests that PRC treatments are suitable for enhancing pear yield and quality, with PRC at 200 ppm being the more recommended option over 300 ppm. This approach serves as an effective strategy for achieving a balance between enhancing the productivity and fruit quality of 'Le-Conte' pears.

This study intended to enhance fruit quality, extend shelf life and maintain quality of ‘Keitt’ mango (Mangifera indica L.) by using edible compounds without affecting quality or taste. Pre-harvest foliar treatment using calcium lactate (CaL) was applied at 1 and 2% alone or in combination with one of the post-harvest dipping treatments of 2% ascorbic acid (AsA) or 0.3% kojic acid (KA), before storage at 4°C for 12 days during two successive seasons. Pre-harvest treatment with calcium lactate at 2% significantly enhanced the quality of ‘Keitt’ mango fruits at harvest. It was observed that all the conducted treatments were effective in maintaining the quality of the pre-prepared ‘Keitt’ mango as compared to the untreated ones. Pre-harvest application of 2% CaL + post-harvest 2% AsA was the most effective treatment under experimental conditions in terms of total phenols, ascorbic acid, TSS/acid ratio, overall appearance, colour purity, browning incidence, and decay percentage. CaL at 2% showed the lowest significant values of CPLW and it maintained the highest significant firmness compared with control.