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.

Blood orange maturation is a complex process and is not fully understood. We studied the on-tree ripening of ‘Sanguinelli’ cultivar picked in 10 stages (S1 to S10) in 4 different fruit sections: peduncle end, proximal and distal equator and stylar end. Results showed that as ripening advanced, chlorophyll decreased and anthocyanin increased, while carotenoid first enhanced (from S1 to S6) and then diminished in the rind, the concentration being dependent on the fruit section. We have found that chlorophylls were higher in the peduncle end and the proximal equator, anthocyanins were higher in the distal equator, while carotenoids were maximum at the peduncle end. Our results demonstrate that flesh anthocyanins, total soluble solids, total acidity increased parallelly to the ripening process, and again these quality attributes were affected by the assayed tissue. Overall, results suggest that the ripening process of ‘Sanguinelli’ blood orange exhibits a gradient pattern.

For consumers, blood oranges with over 25% of peel red colour are considered as commercial fruits (RCF), while lower than 25% are non-commercial fruits (ONCF). The aim of this study was to evaluate, for the first time, the potential of combining preharvest 24-BL (0.01, 0.1, and 1 μM) with non-chilling storage (8 °C) as a synergistic strategy to upgrade ONCF into marketable fruit. Results revealed that 24-BL-treated fruit exhibited redder external and internal colouration, as well as reduced weight loss and increased firmness in both ONCF and RCF. Total anthocyanins and total phenolic compounds were also increased by the treatments. Crucially, all ONCF from 24-BL-treated trees reached the commercial standards of RCF after 20 days of storage, with 0.1 μM being the most effective concentration. Thus, preharvest 24-BL serves as a pioneering tool to maintain the postharvest quality and valorise non-commercial yield blood oranges.

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.