2. Understanding the molecular basis for the crossability of wheat with related species

Previous studies allowed us to "Mendelize" the major crossability QTL, SKr, localised in the distal part of the short arm of chromosome 5B. Furthermore a detailed mapping in an HIF (Heterogeneous inbred family) population of 233 individuals enabled to frame the gene with molecular markers within a genetic interval of 4cM, initiate a physical map in the crossable variety Chinese Spring and establish syntenic relationships with rice and brachypodium in the region. Positional cloning of the gene is planned during the coming months in the context of an innovative project and postdoctoral fellowship funded by the INRA department GAP. The physical map of the locus in the crossable variety Chinese Spring is currently being completed and a map of the non-crossable variety Courtot is being constructed in collaboration with the CNRGV (H. Bergès) in order to anticipate a possible deletion in the crossable variety.

The sequencing of BACs covering the region of the gene will enable the development of new markers and restrict the gene interval to identify candidate genes. Once the candidate gene(s) have been identified, functional validation is planned by transforming an SSD (single seed descent) crossable line and by RNAi on Courtot (non-crossable). Once the gene is isolated, we will study its evolution in different wheat pools, from both a geographical point of view (crossability is only found in bread wheat mostly in the Asiatic pool) and from the temporal point of view (comparisons between diploids, tetraploids and hexaploids), in collaboration with the DGS team so as to better understand the origin of the inhibition of intergeneric crossability. Comparative analyses will also be performed with orthologous genes in other species. The project will also focus on understanding the mode of action of the SKr gene through functional and physiological analyses. Skr Promoter-gene marker constructs (GUS, GFP) will be developed to study in detail the spatial and temporal expression of the gene in transformed plants, while constructs with tagged SKr proteinswill be produced for subcellular localisation analyses. Finally, these data and resources will be exploited to enhance the panel of elite wheat lines that can be crossed with related species, with the aim of broadening the genetic basis of wheat for breeding.