"This project aims to characterize, at the molecular level, the segments of the Brassica napus genome that contain the PrBn locus and a number of other additive or epistatic QTLs controlling homeologous recombination. We will first combine fine genetic mapping and comparative genomic approaches (using Arabidopsis thaliana) to test the core hypothesis that PrBn and most of the mapped QTLs belong to homeologous and / or paralogous regions originating from the amphidiploid nature of the B. napus genome and the large-scale ancestral genome triplication found in its diploid progenitors. We will then screen a B. napus BAC library with markers anchored in the corresponding regions, align the positive BACs into separate contigs spanning the targeted segments and thus generate ""draft"" physical maps of the PrBn region and its duplicates. We will use the rapidly developing genomic resources available for B. rapa and B. oleracea to identify the corresponding regions in the genome of these two diploid species, which are the closest living relatives of B. napus progenitors. This will thus allow a comparative analysis of the microstructure of the PrBn regions and its paralogues and lay the genomic foundation for the long term map-based cloning of PrBn. This project tackles two important aspects of genome evolution related to polyploidy, which is one of the most prominent evolutionary process in plants, including many important crops, and many other eukaryotes: it questions the evolutionary dynamics of duplicated genes/regions, which has a broad significance in biology, and addresses the question of genetic regulation of homeologous chromosome pairing and recombination in allopolyploid species, which is a prerequisite for proper chromosome segregation and reproductive stability in sexual polyploids."