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Abstract :

The heat wave of 28 June 2019 particularly affected winegrowers. The immediate damage (burns on leaves and bunches) led to irreversible losses. However, differences in sensitivity between grape varieties were noted.

The final objective of the thesis project is to identify the grape varieties that are the least sensitive to scorching and that maintain the best performance in the face of these extreme climatic events. The research work will focus on the canopy properties related to these scorch risks on the one hand and to water use efficiency for photosynthesis on the other. In particular, the genetic variability observed in the orientation of leaves, which determines the proportion of solar radiation intercepted by the leaves and clusters, and which largely modulates the risk of scorching, will be analysed. These analyses will be combined with parallel studies on the genetic variability of transpiration, which on the contrary cools the leaves, and on photosynthesis, which interacts with transpiration and determines the water use efficiency and resistance of plants to hot and dry climates in the longer term.

The work will include: 1/ analysis of leaf orientation in a grapevine population set up for association genetics analysis; 2/ experimental studies on blight risk and water use efficiency on a subset of genotypes selected for their contrasting leaf orientations; 3/ in silico analysis, using an existing model, of the impact of changing leaf orientation on blight risk and water use efficiency.