Adapting Portuguese vineyards to climate change: impact of different irrigation regimes on phenolic composition

Abstract

Climate change has led to increased extreme weather events, such as severe droughts and intense rainfall, with regions like Alentejo and Algarve in Portugal, being particularly affected. Some grape varieties are better suited to these conditions due to their ability to close stomata under water stress, reducing water loss through evapotranspiration from the leaves, and potentially leading to increased synthesis of phenolic compounds [1, 2]. Understanding the influence of water availability in concentrating phenolic compounds in autochthonous varieties can be an important tool to adapt to water scarcity while preserving wine typicity and water resources.

This work has been carried out, to analyze the profile of phenolic compounds in four Portuguese red grape varieties: Tinta Gorda, Tinta Miúda, Tinta Caiada, and Moreto. These varieties were cultivated in Reguengos de Monsaraz (Alentejo), under three irrigation regimes (water comfort, moderate water deficit and rainfed) and harvested in 2024. The water comfort regime applied 2686 m³/ha of water, moderate water deficit applied 1343 m³/ha, while the rainfed regime relies solely on natural precipitation. The grape varieties studied are cultivated under organic production practices. The phenolic compounds from the grapes were extracted after 1 hour of maceration with ethanol and analyzed using high-performance liquid chromatography coupled diode array detector (HPLC-DAD).

Nineteen phenolic compounds were identified and quantified in the studied varieties, including anthocyanins, flavanols, flavonols, phenolic acids and stilbenes. In Tinta Gorda, no significant differences were observed between the moderate water deficit and rainfed regimes, although both significantly differed from water comfort. This variety exhibited higher phenolic concentrations under moderate water deficit and rainfed conditions, highlighting its adaptability to water scarcity. Tinta Miúda was the only variety to display significant differences in total phenolic concentrations in all irrigation regimes, with phenolic levels increasing as water availability decreased. Tinta Caiada showed no significant differences between water comfort and moderate water deficit but had the highest phenolic concentration under rainfed conditions, which was statistically distinct from the other irrigation regimes. Moreto exhibited a similar pattern to Tinta Gorda, but its phenolic concentrations decreased with reduced irrigation, likely due to lower grape ripeness under water-scarce conditions.

In summary, the results reveal that Tinta Gorda, Tinta Miúda, and Tinta Caiada varieties exhibit higher concentrations of phenolic compounds under rainfed conditions. Among these, Tinta Miúda and Tinta Caiada stand out as the most statistically promising varieties in terms of adaptability to water scarcity.

Acknowledgement

This research was funded by “Vine&Wine-Driving Sustainable Growth Through Smart Innovation” project (sub-project-BioGrapeSustain), “Mobilizing Agendas for Business Innovation” under the Recovery and Resilience Program. Authors also acknowledge MED https://doi.org/10.54499/UIDB/05183/2020 and CHANGE https://doi.org/10.54499/LA/P/0121/2020.

References

[1] Ramos, M. C., Ibáñez Jara, M. Á., Rosillo, L., Salinas, M. R. (2024). Sci. Hortic., 337, 113475-113484.

[2] Rouxinol, M. I., Martins, M. R., Salgueiro, V., Costa, M. J., Barroso, J. M., Rato, A. E. (2023). Beverages, 9, 8.