Umar Masood Quraishi

Wheat is the primary source of protein in the developing countries. Production of wheat in the world should grow by nearly 25% in the next 15 years to cope with demographic changes. It is therefore important to work on varietal improvement through the identification of genetic determinants of traits of agronomic interest related to yield without loss of intrinsic quality (protein content) or health value and Technology (baking); and in a context of sustainable agriculture more environmentally friendly (especially via the optimization of nitrogen assimilation).

The aim of this thesis is to make an exhaustive inventory of genetic and genomic knowledge related to all of these quantitative traits to identify chromosomal regions that are most relevant in the wheat genome and carrying ‘major’ QTL (i.e. genotype and environment-independent) for their further cloning.

To clearly identify the genomic regions driving traits related to yield and grain quality in diverse genotype, we conducted a meta-analysis of QTL. We identified 302 QTLs involved in yield components, grain protein content, baking and technological as well as health values. Thus, 22 meta-QTL (8 for yield, 8 for grain protein content and 6 for baking quality) were characterized. The vast majority of these QTL were associated with major genes involved in plant development processes such as photoperiod, vernalization ....

The grain fiber content (value quality and health) and nitrogen assimilation (yield component) traits were selected for the identification of candidate genes driving the major associated QTL. The analysis of the synteny between the wheat genome and the sequenced cereal genomes to date such as rice, sorghum, maize and Brachypodium has provided tools (web interface devoted to comparative genomics in cereals) and resources (COS markers for Conserved Orthologous Set) to dissect these QTL.

Regarding the grain fiber content, approaches combining meta-QTL and association genetic at the whole genome level allow the identification of 3 major genomic regions for which 11 candidate genes were studied. For the nitrogen assimilation trait, a QTL conserved at orthologous position in cereals has been cloned by the conventional positional cloning approach, and a single candidate gene is under functional validation.