Cultivar Plasticity in Temperate Fruit Trees Across the Mediterranean Region: Different Combinations of Chill and Heat Lead to Dormancy Release

The Mediterranean Basin, a key region for temperate fruit and nut production, faces significant challenges due to global warming, which disrupts the synchronization of tree phenological cycles with seasonal changes. This study examines the agroclimatic requirements for flowering in four temperate fruit species (almond, apricot, Japanese plum, and sweet cherry) across multiple Mediterranean locations in Spain, Morocco and Tunisia. Using a standardized experimental protocol and the same chill and heat accumulation models (Dynamic and Growing Degree Hours models, respectively), we characterized the dormancy phases and flowering patterns of 17 cultivars, including six that were evaluated for the first time. The results revealed significant variability in chill and heat accumulation across sites, reflecting differences in climatic conditions. While flowering dates were generally consistent across regions, notable differences were observed in the length of the endo-dormancy phase, with longer endo-dormancy periods not always corresponding to higher chill requirements (CR). We found that the climatic region was more important than the year-to-year temperature variability in determining agroclimatic requirements. A compensatory relationship between chill and heat accumulation was observed, indicating cultivar plasticity to adapt and respond to varying environmental conditions. This adaptive capacity in response to fluctuating levels of chill and heat appears to vary among Prunus species. The findings highlight the importance of considering agroclimatic characteristics of cultivars in orchard design to ensure the resilience of temperate fruit crops to climate change. This study provides critical data for improving chill and heat models and underscores the need for further research into phenological plasticity and adaptation traits. The insights gained are intended to support the sustainability of Mediterranean orchards under current and projected climate scenarios.

Agradecemos a la Asociación para la Investigación y la Innovación en el Área Mediterránea (PRIMA), un programa apoyado por H2020, el programa marco de la Unión Europea para la investigación y la innovación, por financiar esta investigación dentro del proyecto AdaMedOr. También agradecemos a los donantes nacionales de los países socios: el Ministerio de Ciencia e Innovación de España (Agencia Estatal de Investigación 10.13039/501100011033) y NextGeneration EU/PRTR (subvenciones PCI2020-111966 y PID2020-115473RR-I00 en el caso de CITA; subvención PCI2020-112113 en el caso de CEBAS); el Ministerio Federal de Educación e Investigación de Alemania (número de subvención 01DH20012), el Ministère de l’Enseignement Supérieure et de la Recherche Scientifique et de l’Innovation, Direction de la Recherche Scientifique et de l’Innovation (MENF-PESRS/DRSI-Maroc) en el caso de Marruecos; y el Ministerio de Educación Superior e Investigación Científica de Túnez en el caso de Túnez.

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