Broadening the genetic diversity of oilseed rape is a major issue. This can be achieved either by crossing B. napus (AnAmCnCn, 2n=38) with its progenitors, B. rapa (ArAr, 2n=20), B. oleracea (CoCo, 2n=18) or by inducing rearrangements between the constitutive A and C genomes of B. napus. In all cases, it is important to monitor homologous and/or homoeologous recombination. When dealing with the progenitors it is possible either to cross them directly with B. napus or to produce synthetic forms (ArArCoCo. 2n=38). Using B. rapa (ArAr, 2n=20), we have shown that the level of homologous recombination between the A genomes is highly dependant on the genomic structure of the hybrid (diploid, digenomic triploid, tetraploid) and on the genetic background. The characterization of synthetic oilseed rape forms and their selfed progeny indicated that chromosome rearrangements occurring between the genomes depend on the genetic backgrounds and on the way the amphidiploids were produced (colchicine-doubling of F1 AC hybrids or through unreduced gametes). The impact of such chromosome rearrangements will be compared to genome dynamics of natural B. napus. In fact, homoeologous recombination between A and C genomes is controlled by a major gene PrBn plus a network of genes. With this genetic system, translocations can be induced, preferentially between the regions of primary homeology in oilseed rape haploids. Our results constitute a general framework to apprehend the evolution and establishment of polyploid species as well as the mechanisms of genetic exchanges between related species for genetic improvement of oilseed rape.
Anne Marie Chèvre Cyril Falentin Michel Renard Maria Manzanares-Dauleux Hortense Brun Régine Delourme Eric Jenczewski Frédérique Eber Martine Leflon Stéphane Nicolas Zhiqian LIU Marie-Odile Lucas Olivier Coriton Nicolas Pouilly Jean-Claude Letanneur
UMR INRA-Agrocampus Rennes, Amélioration des Plantes et Biotechnologies Végé tales, BP35327, 35653 L UMR BiO3P, BP35327, 35653 Le Rheu cedex France Station de génétique et dAmélioration des Plantes, INRA - Institut Jean-Pierre Bourgin, Route de St