Exploitation of the First Sequenced Wheat Chromosome (3B) to Study the Variation of the Recombination Pattern

Wheat (Triticum aestivum L.) is both one of the most important crops grown worldwide and a case study for the evolution of polyploid genomes. Thus, accessing the wheat genome is not only relevant for supporting the identification of genes and variations underlying agronomically important traits to accelerate wheat improvement, but it will also enable a better understanding of the organization, function and evolution of large and polyploid genomes. Meiotic recombination (crossovers) is a mechanism that largely contributes to shape the genome structure in all species. We used a high quality reference sequence of wheat chromosome 3B (2,808 scaffolds representing 833 Mb with a N50 of 892 kb, anchored and oriented using 3075 SNPs) to study the pattern of distribution of recombination events along the chromosome. Using this resource, we concluded that all recombination occurs in only 13% of the chromosome and that ~60% of the genes lying in a large pericentromeric region can only rarely undergo admixture. Comparative analysis of recombination patterns between chromosomes 3A, 3B and 3D reveals high similarity suggesting that recombination events occurs in the most conserved regions (low-copy regions). Analysis of gene-duplication events that are frequent in wheat can partly be explained by recombination, especially regarding tandem duplications.