title: Dissecting tocopherols content in maize (Zea mays L.), using two segregating populations and high-density single nucleotide polymorphism markers.
abstract: BACKGROUND
  Tocopherols, which are vitamin E compounds, play an important role in maintaining human health. Compared with other staple foods, maize grains contain high level of tocopherols.
  
  
  RESULTS
  Two F(2) populations (K22/CI7 and K22/Dan340, referred to as POP-1 and POP-2, respectively), which share a common parent (K22), were developed and genotyped using a GoldenGate assay containing 1,536 single nucleotide polymorphism (SNP) markers. An integrated genetic linkage map was constructed using 619 SNP markers, spanning a total of 1649.03 cM of the maize genome with an average interval of 2.67 cM. Seventeen quantitative trait loci (QTLs) for all the traits were detected in the first map and 13 in the second. In these two maps, QTLs for different traits were localized to the same genomic regions and some were co-located with candidate genes in the tocopherol biosynthesis pathway. Single QTL was responsible for 3.03% to 52.75% of the phenotypic variation and the QTLs in sum explained 23.4% to 66.52% of the total phenotypic variation. A major QTL (qc5-1/qd5-1) affecting α-tocopherol (αT) was identified on chromosome 5 between the PZA03161.1 and PZA02068.1 in the POP-2. The QTL region was narrowed down from 18.7 Mb to 5.4 Mb by estimating the recombination using high-density markers of the QTL region. This allowed the identification of the candidate gene VTE4 which encodes γ-tocopherol methyltransferase, an enzyme that transforms γ-tocopherol (γT)to αT.
  
  
  CONCLUSIONS
  These results demonstrate that a few QTLs with major effects and several QTLs with medium to minor effects might contribute to the natural variation of tocopherols in maize grain. The high-density markers will help to fine map and identify the QTLs with major effects even in the preliminary segregating populations. Furthermore, this study provides a simple guide line for the breeders to improve traits that minimize the risk of malnutrition, especially in developing countries.
authors.affiliation: National Maize Improvement Center of China, China Agricultural University, Beijing 100193, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Shutu
authors.forename: Zhang
authors.initials: Z
authors.lastname: Dalong
authors.forename: Cai
authors.initials: C
authors.lastname: Ye
authors.forename: Zhou
authors.initials: Z
authors.lastname: Yi
authors.forename: Trushar
authors.initials: T
authors.lastname: Shah
authors.forename: Farhan
authors.initials: F
authors.lastname: Ali
authors.forename: Li
authors.initials: L
authors.lastname: Qing
authors.forename: Li
authors.initials: L
authors.lastname: Zhigang
authors.forename: Wang
authors.initials: W
authors.lastname: Weidong
authors.forename: Li
authors.initials: L
authors.lastname: Jiansheng
authors.forename: Yang
authors.initials: Y
authors.lastname: Xiaohong
authors.forename: Yan
authors.initials: Y
authors.lastname: Jianbing
mesh_terms: D053898:Biosynthetic Pathways / Q000235:genetics; D020090:Chromosome Segregation / Q000235:genetics*; D032461:Chromosomes, Plant / Q000235:genetics; D056726:Genetic Association Studies; D008040:Genetic Linkage; D005819:Genetic Markers; D006239:Haplotypes / Q000235:genetics; D006801:Humans; D040582:Inheritance Patterns / Q000235:genetics; D010641:Phenotype; D020161:Physical Chromosome Mapping; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D040641:Quantitative Trait Loci / Q000235:genetics; D019655:Quantitative Trait, Heritable; D024505:Tocopherols / Q000378:metabolism*; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism*
chemical_list: D005819:Genetic Markers; D024505:Tocopherols