Abstract :

Mediterranean viticulture is threatened by climate change. The average rise in temperature is causing disturbances in the functioning of the vine, its development and the composition of the grapes. However, the impact of extreme heat episodes is still poorly understood. In particular, temperature peaks are accompanied by irreversible burns on leaves and bunches with differences in sensitivity between grape varieties. Regions of the genome involved in these variations in sensitivity in grapevines have already been detected in the laboratory. Various processes may be involved, including a disruption of water supply in the leaves or necrosis induced by oxidative stress. The objective of my thesis will be to investigate the main mechanisms that determine these burns in order to better identify their genetic determinants. On the one hand, we will examine candidate genes underlying genomic polymorphisms previously identified through genetic and bioinformatics approaches in grapevine, and the test of homologous candidates in Arabidopsis. On the other hand, we will deploy a mechanistic approach in order to decipher the respective contributions of water supply disruption and oxidative stress in the development of symptoms, using an ecophysiological characterization on grapevine leaves. This project will strengthen the understanding of plant responses to high heat events and their link with water relations within plants. It will provide the genetic basis for the choice of more resistant varieties for future heat waves, a major challenge in improving plant response to multiple abiotic constraints.

Key words: ecophysiology, grapevine, leaf scorch, high temperatures, genetics