Overview of Actual and Ancestral Recombination in Relationship with the Sequence in Wheat: Focus on 3B Chromosome

Communication W794Communication W794Meiotic recombination (crossovers) is a mechanism that largely contributes to shape the genome structure in all species. However, in bread wheat (Triticum aestivum L.), recombination occurs almost exclusively in distal telomeric regions. Thus, many genes contained in pericentromeric regions which represent 80% of the chromosomes are not admixed during meiosis. We exploited the chromosome-survey data from IWGSC to study at the genome scale 596 CO events located on 445 contigs. Among these, more than 250 CO mapped on 25 scaffolds of the 3B pseudomolecule on features smaller than 50kb. This number was increased to reach ~500 COs on 3B which were correlated to sequence features (epigenetic landmarks, genes, transposable elements, specific motifs, RNAseq data of meiosis) available for chromosome 3B. We thus showed that COs mainly occur in the vicinity of genes. Moreover, we used two collections of 90 lines corresponding to Asian and European genetic pools to study the variation of linkage disequilibrium (LD) as well as the ancestral recombination at a finer scale in the regions covering our previously detected hot spots. Analysis revealed high difference in LD structure between the two populations underlying the complex history of each genetic pool. However historical mapping of recombination events using the same SNPs showed a common location of recombination breakpoints with variable intensity. Impact of these results on the improvement of recombination in wheat will be discussed