title: Quantitative trait loci for seed yield and yield-related traits, and their responses to reduced phosphorus supply in Brassica napus.
abstract: OBJECTIVE
  One of the key targets of breeding programmes in rapeseed (Brassica napus) is to develop high-yield varieties. However, the lack of available phosphorus (P) in soils seriously limits rapeseed production. The aim of this study was to dissect the genetic control of seed yield and yield-related traits in B. napus grown with contrasting P supplies.
  
  
  METHODS
  Two-year field trials were conducted at one site with normal and low P treatments using a population of 124 recombinant inbred lines derived from a cross between 'B104-2' and 'Eyou Changjia'. Seed yield, seed weight, seed number, pod number, plant height, branch number and P efficiency coefficient (PEC) were investigated. Quantitative trait locus (QTL) analysis was performed by composite interval mapping.
  
  
  RESULTS
  The phenotypic values of most of the tested traits were reduced under the low P conditions. In total, 74 putative QTLs were identified, contributing 7·3-25·4 % of the phenotypic variation. Of these QTLs, 16 (21·6 %) were detected in two seasons and in the mean value of two seasons, and eight QTLs for two traits were conserved across P levels. Low-P-specific QTLs were clustered on chromosomes A1, A6 and A8. By comparative mapping between Arabidopsis and B. napus, 161 orthologues of 146 genes involved in Arabidopsis P homeostasis and/or yield-related trait control were associated with 45 QTLs corresponding to 23 chromosomal regions. Four gene-based markers developed from genes involved in Arabidopsis P homeostasis were mapped to QTL intervals.
  
  
  CONCLUSIONS
  Different genetic determinants were involved in controlling seed yield and yield-related traits in B. napus under normal and low P conditions. The QTLs detected under reduced P supply may provide useful information for improving the seed yield of B. napus in soils with low P availability in marker-assisted selection.
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, China.
authors.forename: Guangda
authors.initials: G
authors.lastname: Ding
authors.forename: Zunkang
authors.initials: Z
authors.lastname: Zhao
authors.forename: Yuan
authors.initials: Y
authors.lastname: Liao
authors.forename: Yifan
authors.initials: Y
authors.lastname: Hu
authors.forename: Lei
authors.initials: L
authors.lastname: Shi
authors.forename: Yan
authors.initials: Y
authors.lastname: Long
authors.forename: Fangsen
authors.initials: F
authors.lastname: Xu
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D029688:Brassica napus / Q000235:genetics* / Q000378:metabolism*; D002681:China; D002874:Chromosome Mapping; D014644:Genetic Variation; D005838:Genotype; D010758:Phosphorus / Q000378:metabolism*; D040641:Quantitative Trait Loci; D012639:Seeds / Q000254:growth & development* / Q000378:metabolism
chemical_list: D010758:Phosphorus