The intravarietal diversity of sugar concentration in Merlot depends more on late evaporation than sugar loading

The rise in temperature associated with climate change can lead to excessive sugar concentrations at harvest. To maintain varietal typicity in the future, more resilient genotypes need to be identified within clonal diversity. We studied a compendium of compositional and developmental traits in a private collection of 55 accessions and 3 ENTAV-INRA® clones of Merlot. Extensive single berry measurements revealed differences in post phloem arrest water losses at the origin of variations in sugar concentration among the most extreme genotypes.