title: Homoeologous duplicated regions are involved in quantitative resistance of Brassica napus to stem canker.
abstract: BACKGROUND
  Several major crop species are current or ancient polyploids. To better describe the genetic factors controlling traits of agronomic interest (QTL), it is necessary to understand the structural and functional organisation of these QTL regions in relation to genome duplication. We investigated quantitative resistance to the fungal disease stem canker in Brassica napus, a highly duplicated amphidiploid species, to assess the proportion of resistance QTL located at duplicated positions.
  
  
  RESULTS
  Genome-wide association analysis on a panel of 116 oilseed rape varieties genotyped with 3228 SNP indicated that 321 markers, corresponding to 64 genomic regions, are associated with resistance to stem canker. These genomic regions are relatively equally distributed on the A (53%) and C (47%) genomes of B. napus. Overall, 44% of these regions (28/64) are duplicated homoeologous regions. They are located in duplications of six (E, J, R, T, U and W) of the 24 ancestral blocks that constitute the B. napus genome. Overall, these six ancestral blocks have 34 duplicated copies in the B.napus genome. Almost all of the duplicated copies (82% of the 34 regions) harboured resistance associated markers for stem canker resistance, which suggests structural and functional conservation of genetic factors involved in this trait in B. napus.
  
  
  CONCLUSIONS
  Our study provides information on the involvement of duplicated loci in the control of stem canker resistance in B. napus. Further investigation of the similarity/divergence in sequence and gene content of these duplicated regions will provide insight into the conservation and allelic diversity of the underlying genes.
authors.forename: Berline
authors.initials: B
authors.lastname: Fopa Fomeju
authors.forename: Cyril
authors.initials: C
authors.lastname: Falentin
authors.forename: Gilles
authors.initials: G
authors.lastname: Lassalle
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Manzanares-Dauleux
authors.affiliation: INRA, UMR1349 IGEPP, BP35327, 35653 Le Rheu, France. regine.delourme@rennes.inra.fr.
authors.forename: Régine
authors.initials: R
authors.lastname: Delourme
mesh_terms: D029688:Brassica napus / Q000235:genetics* / Q000382:microbiology; D058674:Chromosome Duplication; D002874:Chromosome Mapping; D060467:Disease Resistance / Q000235:genetics*; D017343:Genes, Plant; D056726:Genetic Association Studies; D008040:Genetic Linkage; D005819:Genetic Markers; D014644:Genetic Variation; D018745:Genome, Plant; D055106:Genome-Wide Association Study; D015810:Linkage Disequilibrium; D010935:Plant Diseases / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D011123:Polyploidy; D040641:Quantitative Trait Loci; D019655:Quantitative Trait, Heritable
chemical_list: D005819:Genetic Markers