Heat requirements for grapevine varieties is essential information to adapt plant material in a changing climate

Precocity for fruit ripening is a genetically determined characteristic that is highly variable from one cultivar to another. In traditional wine-growing regions of Europe, growers have used this property to adapt the vines to local climatic conditions in order to maximize terroir expression. Due to global warming, the choice of later ripening grapevine varieties might be necessary in many regions to maintain late ripening conditions favourable for terroir expression. Hence, precise heat requirement data for each grapevine variety is essential information. Phenology (budburst, flowering, veraison and ripeness) and temperature data have been collected for many varieties in a wide range of locations over a great number of vintages. Heat summations base of 10°C were calculated for each variety to reach key phenological stages. However, a more sophisticated agro-climatic model might be necessary to increase the precision of a classification of varieties according to their precocity.