The challenge of adapting grapevine varieties to climate change

Climate change is expected to advance grapevine phenological stages. After the cali- bration and the validation of a degree-days model, we were able to accurately simulate dates of bud- break, flowering and veraison for Riesling and Gewurztraminer, 2 winegrape varieties grown in Alsace, France. Projected daily temperatures were calculated for the local meteorological station with the ARPEGE-Climat general circulation model using 3 distinct greenhouse gas emissions scenarios. Compared with its timing in 1976-2008, veraison is predicted to advance by up to 23 d and mean temperatures during the 35 d following veraison are projected to increase by more than 7°C by the end of the 21st century for both varieties. Such changes will likely have a significant impact on grape and wine quality. Using the same framework, the genetic variability of phenological parameters was explored with 120 genotypes of progeny from a Riesling × Gewurztraminer cross, along with 14 Euro- pean varieties. In addition, we created a virtual late ripening genotype, derived from a cross between Riesling and Gewurztraminer. This modelled genotype was projected to undergo veraison 2 to 3 d before Muscat of Alexandria, one of the latest ripening varieties studied. Even with this virtual geno- type, or with Muscat of Alexandria, grapes would ripen by the middle of the 21st century under higher temperatures than in the present years. This study highlights the important changes that viti- culture will likely face in a future warmer climate and emphasises the need to create very late ripen- ing genotypes or genotypes able to produce high quality wines under elevated temperatures.