Alba Arabia’s research while affiliated with University of Barcelona and other places

BACKGROUND Fluctuations in environmental conditions within fields and crop plant performance can greatly affect production and quality standards. These factors are particularly relevant for producers, who require sustained optimal production to profit from small margins. Fluctuations might be exacerbated at the end of the crop season, where neither of the aforementioned factors are optimal. In the present integrated study, we assess strawberries' nutritional quality and the impact of harvest timing, tunnel conditions and inter‐individual variability in a Mediterranean production tunnel divided into blocks, where two harvests were performed 3 weeks apart. In addition, the effects of sprayed melatonin at the end of productive season were also evaluated. RESULTS End‐season harvesting negatively impacted fruit hydration, antioxidant capacity and ripening‐related hormones in strawberry fruits. Additionally, tunnel distribution influenced fruit nutritional quality, with light radiation being the main variable factor disturbing antioxidant contents. Nutrients exhibited high inter‐individual plant variability, accounting for 20% variation, and were strongly correlated with fruit hydration and ripening‐related phytohormones. Finally, melatonin applications affected neither fruit production, nor nutritional parameters, for which the effects were masked by the intrinsic strawberry variability. Overall, the results underline the limitations of this type of application for field implementation. CONCLUSION Fruit quality variation in strawberry fields is explained by environmental and inter‐individual variability. Likewise, the implementation of regulatory molecules such as melatonin in field applications relies on crop homogeneity and might have limited applicability in heterogeneous productive systems. Consequently, identifying and reducing microclimate variability in productive fields is paramount for advancing agricultural practices to uphold unwavering standards on fruit quality. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Phytohormones are naturally occurring small organic molecules found at low concentrations in plants. They perform essential functions in growth and developmental processes, from organ initiation to senescence, including fruit ripening. These regulatory molecules are studied using different experimental approaches, such as performing exogenous applications, evaluating endogenous levels, and/or obtaining genetically modified lines. Here, we discuss the advantages and limitations of current experimental approaches used to study active biomolecules modulating fruit ripening, focusing on melatonin. Although melatonin has been implicated in fruit ripening in several model fruit crops, current knowledge is affected by the different experimental approaches used, which have given different and sometimes even contradictory results. The methods of application and the doses used have produced different results in studies based on exogenous applications, while different measurement methods and ways of expressing results explain most of the variability in studies using correlative analyses. Furthermore, studies on genetically modified crops have focused on tomato (Solanum lycopersicum L.) plants only. However, TILLING and CRISPR methodologies are becoming essential tools to complement the results from the experimental approaches described above. This will not only help the scientific community better understand the role of melatonin in modulating fruit ripening, but it will also help develop technological advances to improve fruit yield and quality in major crops. The combination of various experimental approaches will undoubtedly lead to a complete understanding of the function of melatonin in fruit ripening in the near future, so that this knowledge can be effectively transferred to the field.

Plum is a stone fruit that stands out for having a short shelf-life because of its high susceptibility to rapid deterioration. Part of this deterioration is explained by fruit overripening. Recently, the role of melatonin in delaying postharvest decay has been investigated but its regulatory function during overripening is still under extensive debate. In this study, to understand physiological events taking place in plums overripening and elucidate the role of melatonin on the postharvest quality of these fruits and its relationship to other plant hormones, Angeleno plums were sprayed with 10⁻⁴M of melatonin solution immediately after harvest. We carried out tissue-specific (mesocarp and exocarp) analysis of total phenols and anthocyanin quantification, as well as the evaluation of different phytohormones by LC-MS/MS and fruit quality parameters. Results showed that during postharvest, endogenous melatonin contents decreased both in the mesocarp and the exocarp of Angeleno plums. Likewise, plum firmness also decreased and a strong correlation was found for this parameter with jasmonic acid (JA) and cytokinins. Conversely, after exogenous melatonin application, endogenous melatonin content increased both in mesocarp and exocarp but it had a differential effect depending on the plum tissue. Indeed, total phenol and anthocyanin contents arose by 21% and 58%, respectively, in the mesocarp after melatonin treatment but no variations were found in the exocarp of Angeleno plums. Hormonal analysis of Angeleno mesocarp also revealed an increase in the JA and its precursor, 12-oxo-phytodienoic acid (OPDA), on the fourth day after melatonin application as well as a positive correlation between melatonin and gibberellin 1 (GA1). These results suggest that melatonin may be acting as a signal molecule increasing phenolic compounds contents through direct regulation and by signaling with other phytohormones. Therefore, this research provides valuable information for understanding the regulatory role of melatonin and its relationship with plant hormones during overripening to contribute to improve the postharvest quality of plums.

The upcoming climate change presents a great challenge for plant growth and development being extremes temperatures among the major environmental limitations to crop productivity. Understanding the repercussions of these extreme temperatures is of high importance to elaborate future strategies to confront crop damages. Tomato plants (Solanum lycopersicum L.) are one of the most cultivated crops and their fruits are consumed worldwide standing out for their organoleptic characteristics and nutritional value. Tomato plants are sensitive to temperatures below 12 °C and above 32 °C. In this study, Micro-Tom cultivar was used to evaluate the effects of extreme temperatures on the plant of tomato and the fruit productivity and quality from the stressed plants, either exposed to cold (4 °C for three nights per week) or heat (32 °C during the day, seven days per week) treatments. Total productivity and the percentage of ripe fruits per plant were evaluated together with foliar stress markers and the contents of photosynthetic pigments and tocochromanols. Fruit quality was also assessed determining lycopene contents, total soluble solids, total acidity and ascorbate contents. High temperatures altered multiple physiological parameters indicating a moderate stress, particularly decreasing fruit yield. As a response to this stress, plants enhanced their antioxidant contents both at leaf and fruit level. Low temperatures did not negatively affect the physiology of plants with similar yields as compared to controls, suggesting chilling acclimation. Both high and low temperatures, but most particularly the former, increased total soluble solids contents indicating that temperature control may be used as a strategy to modulate fruit quality.

Tocochromanols are a group of lipid-soluble antioxidants that include tocopherols, tocotrienols and plastochromanol-8. Here, we examined a putative differential accumulation of tocochromanols in photosynthetic and non-photosynthetic tissues (including leaves and whole fruits) of strawberry (Fragaria x ananassa cv. Albion) plants and evaluated their endogenous variations in response to a reiterated water deficit during a vegetative (non-productive) and a fruiting (productive) period. In addition, we evaluated the concentration of tocochromanols in achenes (true fruits) and flesh of strawberries (whole fruits) at the white and full-red stages both under optimal and stress conditions. Results showed that leaves mainly accumulated α-tocopherol, with plastochromanol-8 and γ-tocopherol being present at low amounts. In contrast, whole fruits did not accumulate plastochromanol-8, γ-tocopherol being the major tocochromanol in the achenes (true fruit) and α-tocopherol in the flesh. While α-tocopherol content in leaves increased up to seven-fold after 12 weeks of stress during the fruiting period, it kept unaltered during the vegetative period. Neither plastochromanol-8 nor γ-tocopherol contents increased in leaves of stressed plants. During the fruiting period, γ-tocopherol content increased in whole fruits of stressed plants (most of it being accumulated in the achenes). Among the compounds examined, the flesh of strawberries accumulated α-tocopherol only, both at the white and full-red stages. It is concluded that (i) α-tocopherol is the major tocochromanol in leaves, while γ-tocopherol is the major tocochromanol in achenes (ii) reiterated water deficit promotes the accumulation of α-tocopherol in leaves and γ-tocopherol in fruits, (iii) α-tocopherol not only accumulates in photosynthetic tissues (leaves and whole fruits at green stages), but also in non-photosynthetic tissues (flesh of whole fruits at the white and full-red stages), and (iv) achenes (true fruits) of strawberry plants are an extraordinary rich source of tocopherols.