title: Seedling development traits in Brassica napus examined by gene expression analysis and association mapping.
abstract: BACKGROUND
  An optimal seedling development of Brassica napus plants leads to a higher yield stability even under suboptimal growing conditions and has therefore a high importance for plant breeders. The objectives of our study were to (i) examine the expression levels of candidate genes in seedling leaves of B. napus and correlate these with seedling development as well as (ii) detect genome regions associated with gene expression levels and seedling development traits in B. napus by genome-wide association mapping.
  
  
  RESULTS
  The expression levels of the 15 candidate genes examined in the 509 B. napus inbreds showed an averaged standard deviation of 5.6 across all inbreds and ranged from 3.2 to 8.8. The gene expression differences between the 509 B. napus inbreds were more than adequate for the correlation with phenotypic variation of seedling development. The average of the absolute value correlations of the correlation coefficients of 0.11 were observed with a range from 0.00 to 0.39. The candidate genes GER1, AILP1, PECT, and FBP were strongly correlated with the seedling development traits. In a genome-wide association study, we detected a total of 63 associations between single nucleotide polymorphisms (SNPs) and the seedling development traits and 31 SNP-gene associations for the candidate genes with a P-value < 0.0001. For the projected leaf area traits we identified five different association hot spots on the chromosomes A2, A7, C3, C6, and C7.
  
  
  CONCLUSIONS
  A total of 99.4% of the adjacent SNPs on the A genome and 93.0% of the adjacent SNPs on the C genome had a distance smaller than the average range of linkage disequilibrium. Therefore, this genome-wide association study is expected to result on average in 14.7% of the possible power. Compared to previous studies in B. napus, the SNP marker density of our study is expected to provide a higher power to detect SNP-trait/-gene associations in the B. napus diversity set. The large number of associations detected for the examined 14 seedling development traits indicated that these are genetically complex inherited. The results of our analyses suggested that the studied genes ribulose 1,5-bisphosphate carboxylase/oxygenase small subunit (RBC) on the chromosomes A4 and C4 and fructose-1,6-bisphosphatase precursor (FBP) on the chromosomes A9 and C8 are cis-regulated.
authors.affiliation: Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, Köln, 50829, Germany. koerber@mpipz.mpg.de.|Institute of Crop Science and Resource Conservation, Plant Breeding and Biotechnology, University of Bonn, Katzenburgweg 5, Bonn, 53115, Germany. koerber@mpipz.mpg.de.
authors.forename: Niklas
authors.initials: N
authors.lastname: Körber
authors.affiliation: Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, Köln, 50829, Germany. bus@mpipz.mpg.de.|Institute of Crop Science and Resource Conservation, Plant Breeding and Biotechnology, University of Bonn, Katzenburgweg 5, Bonn, 53115, Germany. bus@mpipz.mpg.de.
authors.forename: Anja
authors.initials: A
authors.lastname: Bus
authors.affiliation: Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, Köln, 50829, Germany. jqli@mpipz.mpg.de.
authors.forename: Jinquan
authors.initials: J
authors.lastname: Li
authors.affiliation: The Genome Analysis Centre, Norwich Research Park, Norwich, NR4 7UH, UK. Janet.Higgins@tgac.ac.uk.
authors.forename: Janet
authors.initials: J
authors.lastname: Higgins
authors.affiliation: John Innes Centre, Norwich Research Park, NR4 7UH, Norwich, UK. ian.bancroft@york.ac.uk.|Department of Biology, Wentworth Way, University of York, Heslington, York, YO41 5DD, UK. ian.bancroft@york.ac.uk.
authors.forename: Ian
authors.initials: I
authors.lastname: Bancroft
authors.affiliation: Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N OX2, Canada. Erin.Higgins@AGR.GC.CA.
authors.forename: Erin Eileen
authors.initials: EE
authors.lastname: Higgins
authors.affiliation: Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N OX2, Canada. isobel.parkin@agr.gc.ca.
authors.forename: Isobel Alison Papworth
authors.initials: IA
authors.lastname: Parkin
authors.affiliation: Department of Plant Breeding, Research Centre for BioSystems, Land Use and Nutrition, Justus Liebig University, Heinrich-Buff-Ring 26-32, Giessen, 35392, Germany. Bertha.M.Salazar-Colqui@agrar.uni-giessen.de.
authors.forename: Bertha
authors.initials: B
authors.lastname: Salazar-Colqui
authors.affiliation: Department of Plant Breeding, Research Centre for BioSystems, Land Use and Nutrition, Justus Liebig University, Heinrich-Buff-Ring 26-32, Giessen, 35392, Germany. Rod.Snowdon@agrar.uni-giessen.de.
authors.forename: Rod John
authors.initials: RJ
authors.lastname: Snowdon
authors.affiliation: Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, Köln, 50829, Germany. stich@mpipz.mpg.de.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Stich
mesh_terms: D029688:Brassica napus / Q000235:genetics* / Q000254:growth & development*; D002874:Chromosome Mapping; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D005787:Gene Frequency / Q000235:genetics; D053263:Gene Regulatory Networks; D020043:Genes, Essential; D017343:Genes, Plant; D055106:Genome-Wide Association Study; D007178:Inbreeding; D015810:Linkage Disequilibrium / Q000235:genetics; D010641:Phenotype; D018515:Plant Leaves / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D019655:Quantitative Trait, Heritable; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics; D036226:Seedlings / Q000235:genetics* / Q000254:growth & development*
chemical_list: D012273:Ribulose-Bisphosphate Carboxylase