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PhD defended october 17th, 2014
Direction: Régine Delourme

Abstract:

All crop species are recent or ancient polyploids and have more or less duplicated genomes. Following polyploidy events, structural and functional modifications result in differential gene content or regulation in the duplicated regions, which can play a fundamental role in the diversification of the genes underlying complex traits. To better understand the functioning of the genetic factors controlling the agronomic traits, it is necessary to analyze them in the light of the duplications in the genome. We have addressed this issue in oilseed rape, a species with a highly duplicated genome, with the aim of studying the consequences of genome duplications on the structural and functional organization of the genomic regions involved in quantitative resistance to stem canker. Numerous genomic regions were identified, which confirmed the high polygenic nature of this resistance. Their distribution was quite equivalent between A and C genomes of oilseed rape but a bias was observed in relation with the subgenomes deriving from the ancestral triplication event of Brassica clade. At least 44% of the genomic regions corresponded to homoeologous duplicated regions of five Arabidopsis thaliana syntenic blocks.
A comparative genomic analysis with A. thaliana showed that many genes maintained in several duplicated regions were involved in the stress response, which converges with the results obtained in other species. Comparative genomics also allowed us to draw hypotheses on the function of genes underlying the QTL located in these genomic regions.