Brassinosteroids (BRs), a new family of plant hormones, have been used in a range of food staples, oil crops, and cereals. However, the scientific literature pertaining to their use in fleshy fruits remains scarce. This review presents, for the first time, the knowledge developed over the last decade on the role of BR preharvest treatments in crop yield and fruit quality properties at harvest and during storage, although information about the effects of BR postharvest treatments is also addressed. This review revealed that 24-epibrassinolide is the most used BR analogue in research experiments, either as a pre- or postharvest treatment, with doses ranging from 0.1 to 15 μM. Additionally, most of the research has been conducted on non-climacteric fruit species. In most of these preharvest treatments, an increase in crop yield has been reported, as well as enhanced anthocyanin concentration in red-coloured fruit. In addition, increases in firmness, total soluble solids, and phenolic content have also been observed. On the other hand, BR postharvest treatments led to the maintenance of these fruit quality properties during storage due to increased antioxidant systems, either enzymatic or non-enzymatic ones. Finally, as future perspectives, it is proposed to extend the research about BR treatments to other climacteric fruits and to deepen the knowledge of how BRs regulate physiological aspects from preharvest to postharvest. Furthermore, it is essential to investigate the role of BRs in the prevention of rot and biotic stress.

Polyamines (PAs) are low-molecular-weight compounds that contain amino groups. PAs are present in a variety of organisms, including plants, animals and microorganisms. In plants, the main PAs are putrescine (PUT), spermidine (SPD) and spermine (SPM). They play crucial physiological roles in plant development, including flowering, fruit set, growth, ripening and metabolic processes. In addition, PAs are components of the diet and have a role in health and disease. Furthermore, PAs have been demonstrated to help overcome the negative effects of adverse environmental factors of both biotic and abiotic stresses. Thus, the main objective of this review was to examine the recent literature regarding the mentioned effects of PAs apart from the impact of preharvest PAs treatments, applied at different stages of fruit development, on fresh fruit crop yield and fruit quality properties at harvest, and in their maintenance during storage, with a special emphasis on the fruit content in bioactive compounds with antioxidant activity. Moreover, this review addressed the impact of PAs on other physiological processes affecting crop yield such as flowering and fruit set.

Melatonin (MEL), also known as N-acetyl-5-methoxytryptamine, has been reported in plants as a secondary messenger involved in regulating abiotic stress responses. MEL treatment, either preharvest or postharvest, regulates several physiological and biochemical processes during fruit growth and ripening in horticultural products. These include reproductive development, tissue and quality maintenance, delayed senescence, and responses to abiotic stress. Due to its natural origin, low toxicity, and multifunctional regulatory capacity, MEL has recently attracted attention as a promising ‘green preservative’ for sustainable postharvest management. Additionally, MEL coordinates through cross-talk with other plant hormones, such as abscisic acid, ethylene, polyamines, jasmonic acid, γ-aminobutyric acid, salicylic acid, and nitric oxide, to regulate postharvest ripening and senescence. Furthermore, MEL enhances antioxidant systems and improves membrane integrity, thereby alleviating chilling injury and enhancing fruit firmness and colour. Notably, recent evidence highlights the innovative regulatory mechanisms of MEL involving redox homeostasis, hormone signalling reprogramming, and transcriptional modulation of stress-responsive pathways. MEL could therefore be considered an emerging, eco-friendly tool for prolonging the shelf-life of fruit and vegetables and maintaining their quality. This review summarises the mechanisms by which MEL contributes to plant stress resistance by regulating the biosynthesis and metabolism of stress tolerance and improving fruit quality.

Nowadays, increasing consumer awareness of the link between diet and health has underscored the value of bioactive compounds in preventing metabolic disorders. In this frame, blood oranges are highly appreciated for their unique phytochemical profile, including anthocyanins along with flavanones with recognised health‐promoting benefits. This study explores, for the first time, the combined effect of preharvest and postharvest melatonin treatments, along with cold storage, on the accumulation of endogenous melatonin, phenolic compounds and vitamin C in blood orange ( Citrus sinensis L. Osbeck) cv. ‘Sanguinelli’. HPLC‐QqQ‐MS/MS and HPLC‐DAD methodologies were used to analyse the bioactive compounds in leaves, flavedo, albedo and juice. The findings demonstrate that exogenous melatonin is an effective strategy to enhance the functional quality of blood oranges. Preharvest treatments increased endogenous melatonin levels in the leaves, flavedo and albedo, either by positive absorption or enhancement of biosynthetic pathways. However, postharvest melatonin treatments combined with cold storage led to the highest endogenous melatonin accumulation, suggesting a synergistic effect between exogenous supply and stress‐induced biosynthesis. Furthermore, melatonin treatments promoted the accumulation of flavanones, anthocyanins and vitamin C, although cold storage remained the key driver of anthocyanin biosynthesis. These findings highlight the potential of melatonin as a natural elicitor to improve the functional quality of blood oranges, identifying preharvest melatonin treatment at 1 mM combined with cold storage as the most effective strategy. Nonetheless, further studies on bioavailability and bioactivity are required to determine whether these enhancements translate into greater health benefits for consumers.

Chronic metabolic disorders have increased recently due to changes in dietary habits and lifestyle. Red-coloured fruits, such as sweet cherries, are rich in anthocyanins and other (poly)phenolic compounds with health-promoting properties, which has garnered growing scientific interest. Melatonin elicitation has emerged as a promising strategy to improve the functional quality of these fruits. This research investigates, for the first time, the combined effect of pre- and postharvest melatonin treatments, followed by a cold storage (2 °C) of 21 days, on the endogenous melatonin and phenolic compound levels of 90 sweet cherries (n = 3) from the ‘Sunburst’ cultivar and harvested from 9 trees per treatment. Single preharvest or postharvest melatonin treatments increased the endogenous melatonin content via direct absorption and activation of key biosynthetic genes, while they reduced anthocyanin, hydroxycinnamic acid, and flavonol levels, likely due to a ripening-delaying effect at harvest. Nevertheless, the combined treatment increased endogenous melatonin levels 5-fold compared to harvest and increased all measured polyphenolic compound levels, including a 29% rise in total anthocyanins reverting the delay in the ripening process. These effects suggest upregulation of genes in the phenylpropanoid pathway and could improve fruit’s functional quality. The response to melatonin is cultivar- and dose-dependent. Future research should investigate genetic and transcriptomic validation to confirm these potential effects and assess whether increased bioactive compound content would translate into measurable human health benefits.

Sweet cherry (Prunus avium L.) is a highly appreciated fruit species for consumption but susceptible to climate change-induced weather, such as heavy rainfall, which catastrophically compromises yield and commercial fruit quality. Brassinosteroids (BRs) represent a novel biologically safe class of hormones that have been shown to increase plant resilience against these adversities and enhance crop yield and fruit quality in some fruit species. The main aim of this study was to evaluate the potential efficacy of the preharvest foliar spray treatments with 24-epibrassinolide (24-BL) at 0.01, 0.1 and 1 µM on crop yield, cracking incidence and fruit quality of ‘Sunburst’ and ‘Skeena’ sweet cherry cultivars, during two seasons with different weather conditions (2022 and 2023). Results revealed that 24-BL treatments improved fruit growth, fruit weight, and increased commercial crop yield, especially at 0.1 µM during the first season. Notably, in 2023, when extreme rainfall occurred, 24-BL at 0.01 and 0.1 µM significantly decreased cracking incidence by up to 50% for ‘Skeena’. Additionally, firmness, red colour and bioactive compounds, such as total phenolics and total anthocyanins, were also found at higher levels in fruits from 24-BL-treated trees compared to controls, in both cultivars and years. In conclusion, the foliar spray application of 24-BL at 0.01 µM and, especially at 0.1 µM, can be a useful and eco-friendly tool to reduce cracking incidence, improve crop yield and enhance sweet cherry quality traits regardless of environmental negative events, such as heavy rainfall. Importantly, the enhancement of bioactive compounds would promote additional antioxidant properties and enhance health benefits to consumers.