Abstract :

In the context of climate change, crops will be more frequently subjected to extreme weather events. Continued progress on maize yield requires consideration of new genetic methods to characterise the comparative advantages of genotypes under drought and high temperature conditions. The main objective of this thesis is to improve the knowledge of genetic control of maize yield and its components under water and heat stress in a field trial network. For this purpose, we used data from the EU DROPS project and the French Amaizing project with 29 field trials distributed in Europe and Chile, in 2012 and 2013, with irrigated and non-irrigated treatments in each site. A precise characterisation of the environmental conditions was carried out, as well as a precise measurement of phenology and yield and its components on a panel of 244 maize hybrids. The approach used in this thesis was to use the precise environmental characterisation at each site to dissect the interactions between genotype and environment. In a first step we classified the 29 trials into six environmental scenarios that had been previously defined over long climate series across Europe. The genomic regions associated with yield had highly variable effects between sites, depending on the environmental scenarios. Each allele can therefore be associated with a region in Europe where it has a high probability of positive effect. In a second step, by combining platform and field data, we estimated the yield responses to radiation intercepted during the vegetative period, and to temperature and water deficit at flowering. We identified the genomic regions associated with these responses, making the genotypes analysed tolerant or sensitive to the variable considered. This work opens up prospects for plant improvement in a context of climate change.