Maria Isabel Escribano

Maintaining the nutritional and functional quality of blueberries during cold storage remains a postharvest challenge. This study evaluated the effects of short-term high-CO₂ treatments on phenylpropanoid-related metabolism in two commercially important blueberry cultivar–season combinations: Duke (Vaccinium corymbosum L., highbush; early-season, June harvest) and Ochlockonee (V. virgatum Aiton, rabbiteye; late-season, September harvest). Fruits were exposed to 15% or 20% CO₂ for 3 days at 1 °C and subsequently stored for up to 29 days at 1 °C. Phenolic compounds, antioxidant capacity, and the expression of selected phenylpropanoid-related genes, including flavonoid biosynthetic enzymes and R2R3-MYB transcription factors, were analyzed. Short-term CO₂ treatments were associated with transient transcriptional responses, particularly in anthocyanin-related pathways, together with genotype-associated differences in phenolic composition and antioxidant capacity during storage. Overall, the results indicate associations between CO₂ exposure and secondary metabolism under cold storage conditions and should be interpreted as correlative rather than mechanistic evidence of priming.

Arabinogalactan proteins (AGPs) and extensins influence cell wall assembly and regulate plant cell mechanical properties through interactions with extracellular matrix polymers. These proteins may play a key role in the biochemical events underlying postharvest treatments aimed at controlling fruit texture and turgor loss associated with senescence-related disorders. We studied the temporal and spatial accumulation patterns of extensin and AGP isoforms constitutively expressed along with the profiling of nucleotide sugars UDP-galactose, UDP-arabinose, UDP-glucuronic acid, and UDP-rhamnose in Mara des Bois strawberries under different storage conditions. We also assessed the expression timing of AGP-encoding genes (FvAFP4, FvAGP5) and genes involved in key steps of post-translational glycosylation (FvP4H1, FvGAT20, FvGAT7). Whereas extensins are down-regulated, AGPs are transcriptionally regulated by cold and cold-high CO₂ and post-translationally modulated after transfer to 20 °C. Based on their subcellular localization, molecular properties, isoform-specific glycosylation, UDP-sugar availability, and timing-regulated expression, AGPs are likely involved in cell wall assembly and modulation of mechanical properties. Consequently, they may influence fruit texture and enhanced softening resistance, potentially counteracting senescence-associated disorders through CO₂-responsive signaling mechanisms. Conversely, the decrease in both UDP-galactose levels and AGPs gene expression in non-cold-stored senescent strawberries at 20 °C further supports their relevance in AGPs biosynthesis regulation and underscores their potential as markers for improving postharvest storage strategies.

Raspberries (Rubus idaeus L.) are valued as both a food source and a medicinal plant, with expanding production driven by premium market demand. Primocane varieties, such as “Regina” are prized for their ability to produce two harvests per year, offering extended availability into autumn and providing significant commercial benefit. Their high polyphenol content, particularly in anthocyanins and flavonoids, contributes to antioxidant and health properties. However, their extraction and quantification are influenced by factors such as genetic variability, environmental conditions, fruit maturity, storage, and processing techniques. This study analyzed the metabolic profiles of “Regina” raspberries harvested in June (RiJ) and September (RiS). Out of 748 compounds listed in the Phenol-Explorer database, 377 metabolites were identified and categorized. Principal component analysis (PCA) revealed significant differences between harvests, with RiS samples showing higher concentrations of most flavonoid and non-flavonoid compounds. Heatmap and volcano plot analyses confirmed that significant metabolites were enriched in RiS samples. Correspondingly, antioxidant capacity, measured via ABTS and FRAP assays, was higher in RiS raspberries. These findings highlight the metabolic and antioxidant differences between harvest periods and lay the groundwork for understanding how these compounds could be modulated through the application of postharvest treatments.

The global demand for blueberries has increased due to their health benefits, but postharvest losses, particularly firmness loss and decay, present significant challenges. This study evaluated the effects of high CO₂ concentrations (15% and 20%) applied for 3 d at 1.0 °C on highbush (cv. ‘Duke’) and rabbiteye (cv. ‘Ochlockonee’) blueberries, with a focus on quality maintenance during cold storage. The quality parameters evaluated included titratable acidity, pH, total soluble solids, weight loss, and decay. The effect of gaseous treatments on firmness was analyzed using mechanical parameters and the expression of genes related to cell wall integrity (XTH23, PL8, PG, PM3, EXP4, and VcGH5). Treatment efficacy varied between species. High CO₂ levels reduced decay in both cultivars, but only the highbush cultivar (‘Duke’) showed improvements in firmness. In ‘Duke’, CO₂ treatments affected the expression of XTH23, PL8, and GH5, while the role of PG and PME in maintaining firmness was minimal, with no significant differences between treatments. In ‘Ochlockonee’, CO₂ effectively reduced weight loss but did not improve firmness. In conclusion, these results highlight the need for tailored postharvest strategies for different blueberry cultivars and suggest that short-term high CO₂ treatments may effectively prolong the postharvest life of highbush blueberries.

Global demand for blueberries has surged in recent years, primarily due to their health benefits. However, blueberries postharvest losses, particularly firmness loss and decay, remain significant challenges. This study applied high concentrations of CO2 (15% and 20%) for 3 days at 1 °C to highbush (Duke) and rabbiteye (Ochlockonee) blueberries to assess their effects on maintaining quality, especially firmness, during low-temperature storage. Various quality parameters were evaluated, including titratable acidity, pH, total soluble solids, weight loss, and decay. The impact of gaseous treatments on firmness was analysed through mechanical parameters and the expression of genes related to cell wall integrity (XTH23, PL8, PG, PM3, EXP4, and VcGH5). The effectiveness of the treatments varied between species. High CO2 levels successfully reduced decay in both cultivars, but only the highbush variety (Duke) showed improvements in firmness. In Duke, CO2 treatments influenced the expression of genes associated to cell wall integrity, such as XTH23, PL8, and GH5. In contrast, the roles of PG and PME in firmness maintenance were minimal, showing no significant differences between treatments. While CO2 did not enhance firmness in Ochlockonee, it effectively reduced weight loss, highlighting the need for tailored postharvest strategies for different blueberry cultivars.

Blueberries (Vaccinium corymbosum L.) are becoming increasingly popular for their nutritional and health benefits, and their economic value is therefore increasing. The loss of quality that can occur due to softening and fungal attack is an important consideration when marketing blueberries. Despite the added value of blueberries, no studies have been carried out on how the fruit arrives at the outlets just before purchase by the consumer in terms of firmness, physico-chemical parameters, phenolic compounds, and fungal growth. The aim of this work has been, therefore, to investigate possible differences in quality parameters between blueberries purchased from ten different outlets, regardless of the supplier. The results showed that all the samples were of acceptable quality, although they all had a low maturity index at the point of sale. None of the samples studied showed clear signs of fungal decay at the time of purchase, although we were able to grow and identify some pathogen specimens after cultivation. In terms of total phenolic and anthocyanin content, as well as antioxidant activity, all the samples showed low values, possibly due to their postharvest storage, but they were within the expected range for this fruit. On the other hand, differences in the measured parameters were observed between samples of the same cultivar while no differences were found between conventionally and organically grown blueberries. This suggests that preharvest (such as edaphoclimatic conditions, agricultural practices, and cultivars) and postharvest factors (such as treatments used, storage, and transport temperatures) could influence the berry quality when they reach the consumer.

Short-term gaseous treatments improve rachis quality during table grape postharvest, but little is known about the mechanisms involved. In this work, we observed that the application of a 3-day CO₂ treatment at 0 °C improved rachis browning of Superior Seedless and Red Globe bunches, affecting the non-enzymatic antioxidant system by reducing the total phenolic content, the antioxidant activity and the expression of different stilbene synthase genes. Lipid peroxidation levels revealed lower oxidative stress in CO₂-treated rachis of both cultivars linked to the activation of the enzymatic antioxidant system. Furthermore, whereas a positive correlation was denoted between rachis browning and the accumulation of key ABA regulatory genes in Red Globe bunches, this effect was restricted to ACS1, a key synthetic ethylene gene, in Superior Seedless clusters. This work also corroborated the important role of ethylene-responsive factors in the beneficial effect of the gaseous treatment, not only in the berries but also in the rachis. Finally, the application of the gaseous treatment avoided the induction of cell wall-degrading enzyme-related genes in both cultivars, which could favor the maintenance of rachis quality. This work provides new insight into specific responses modulated by the gaseous treatment focused on mitigating rachis browning independently of the cultivar.

Despite the fact that many studies have examined the effectiveness of different gaseous postharvest treatments applied at low temperature to maintain table grape quality, the use of ethanol vapor has hardly been investigated. Thus, this work has studied the effectiveness of ethanol vapor-generating sachets in the maintenance of It 681–30 table grape quality, a new cultivar, during storage at low temperature and after the shelf-life period at 20 °C. To this end, various quality assessments have been carried out and the effect of the ethanol treatment on the expression of different genes (phenylpropanoids, transcription factors, PRs, and aquaporins) was determined. The results indicated that the application of ethanol vapor reduced the total decay incidence, weight loss, and the rachis browning index in It 681–30 grapes stored at 0 °C and after the shelf-life period at 20 °C, as compared to non-treated samples. Moreover, the modulation of STS7 and the different PR genes analyzed seems to play a part in the molecular mechanisms activated to cope with fungal attacks during the postharvest of It 681–30 grapes, and particularly during the shelf-life period at 20 °C. Furthermore, the expression of aquaporin transcripts was activated in samples showing higher weight loss. Although further work is needed to elucidate the role of ethanol in table grape quality, the results obtained in this work provide new insight into the transcriptional regulation triggered by ethanol treatment.