title: Unraveling the genetic basis of seed tocopherol content and composition in rapeseed (Brassica napus L.).
abstract: BACKGROUND
  Tocopherols are important antioxidants in vegetable oils; when present as vitamin E, tocopherols are an essential nutrient for humans and livestock. Rapeseed (Brassica napus L, AACC, 2 n = 38) is one of the most important oil crops and a major source of tocopherols. Although the tocopherol biosynthetic pathway has been well elucidated in the model photosynthetic organisms Arabidopsis thaliana and Synechocystis sp. PCC6803, knowledge about the genetic basis of tocopherol biosynthesis in seeds of rapeseed is scant. This project was carried out to dissect the genetic basis of seed tocopherol content and composition in rapeseed through quantitative trait loci (QTL) detection, genome-wide association analysis, and homologous gene mapping.
  
  
  RESULTS
  We used a segregating Tapidor × Ningyou7 doubled haploid (TNDH) population, its reconstructed F(2) (RC-F(2)) population, and a panel of 142 rapeseed accessions (association panel). Genetic effects mainly contributed to phenotypic variations in tocopherol content and composition; environmental effects were also identified. Thirty-three unique QTL were detected for tocopherol content and composition in TNDH and RC-F(2) populations. Of these, seven QTL co-localized with candidate sequences associated with tocopherol biosynthesis through in silico and linkage mapping. Several near-isogenic lines carrying introgressions from the parent with higher tocopherol content showed highly increased tocopherol content compared with the recurrent parent. Genome-wide association analysis was performed with 142 B. napus accessions. Sixty-one loci were significantly associated with tocopherol content and composition, 11 of which were localized within the confidence intervals of tocopherol QTL.
  
  
  CONCLUSIONS
  This joint QTL, candidate gene, and association mapping study sheds light on the genetic basis of seed tocopherol biosynthesis in rapeseed. The sequences presented here may be used for marker-assisted selection of oilseed rape lines with superior tocopherol content and composition.
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, China.
authors.forename: Xingxing
authors.initials: X
authors.lastname: Wang
authors.forename: Chunyu
authors.initials: C
authors.lastname: Zhang
authors.forename: Lingjuan
authors.initials: L
authors.lastname: Li
authors.forename: Steffi
authors.initials: S
authors.lastname: Fritsche
authors.forename: Jessica
authors.initials: J
authors.lastname: Endrigkeit
authors.forename: Wenying
authors.initials: W
authors.lastname: Zhang
authors.forename: Yan
authors.initials: Y
authors.lastname: Long
authors.forename: Christian
authors.initials: C
authors.lastname: Jung
authors.forename: Jinling
authors.initials: J
authors.lastname: Meng
mesh_terms: D000818:Animals; D029741:Brassica rapa / Q000235:genetics / Q000378:metabolism; D002874:Chromosome Mapping; D056726:Genetic Association Studies; D055106:Genome-Wide Association Study; D006238:Haploidy; D006801:Humans; D010938:Plant Oils / Q000378:metabolism; D011153:Population / Q000235:genetics; D040641:Quantitative Trait Loci / Q000235:genetics*; D012639:Seeds / Q000235:genetics / Q000378:metabolism; D024505:Tocopherols / Q000737:chemistry / Q000378:metabolism*
chemical_list: D010938:Plant Oils; D024505:Tocopherols