Résumé
Grapevine yield sustainability under global warming is a major issue. A hypothesis is that long-term elevated temperatures may cause the failure of key phases of reproductive development, through their negative impact on carbon balance. However, testing the specific role of plant carbon status on yield elaboration under elevated temperatures is difficult on perennial crops, such as grapevine, and when environment fluctuates. To overcome these difficulties, the present work was conducted under fully controlled environment using Microvine, a new model for grapevine genetics and physiological studies. Five experiments were performed ingrowth chambers, applying contrasted day/night temperature over a one- to two-month period. Plant phenology, vegetative development and yield components were assessed before and after temperature treatments. In addition, the biomass growth and sugar contents of all individual above-ground organs and of roots were determined at harvest. High temperatures caused inflorescence abscission, but did not change flower and berry numbers on the remaining bunches. Flowering and véraison were also delayed by warm temperatures, on a thermal time basis. In contrast, plant phyllochron and biomass accumulation were unchanged. Carbon status in roots was altered under high temperatures, thus indicating carbon gain was impaired with sink demand. These results suggest that dynamics of carbohydrate pool within perennial organs act as an adjusting variable to buffer changes in carbon balance. This study provides the first basis for a modelling approach of yield responses to carbon balance under climate changes