title: Identification and characterization of improved nitrogen efficiency in interspecific hybridized new-type Brassica napus.
abstract: OBJECTIVE
  Oilseed rape (Brassica napus) is an important oil crop worldwide. The aim of this study was to identify the variation in nitrogen (N) efficiency of new-type B. napus (genome A(r)A(r)C(c)C(c)) genotypes, and to characterize some critical physiological and molecular mechanisms in response to N limitation.
  
  
  METHODS
  Two genotypes with contrasting N efficiency (D4-15 and D1-1) were identified from 150 new-type B. napus lines, and hydroponic and pot experiments were conducted. Root morphology, plant biomass, N uptake parameters and seed yield of D4-15 and D1-1 were investigated. Two traditional B. napus (genome A(n)A(n)C(n)C(n)) genotypes, QY10 and NY7, were also cultivated. Introgression of exotic genomic components in D4-15 and D1-1 was evaluated with molecular markers.
  
  
  RESULTS
  Large genetic variation existed among traits contributing to the N efficiency of new-type B. napus. Under low N levels at the seedling stage, the N-efficient new-type D4-15 showed higher values than the N-inefficient D1-1 line and the traditional B. napus QY10 and NY7 genotypes with respect to several traits, including root and shoot biomass, root morphology, N accumulation, N utilization efficiency (NutE), N uptake efficiency (NupE), activities of nitrate reductase (NR) and glutamine synthetase (GS), and expression levels of N transporter genes and genes that are involved in N assimilation. Higher yield was produced by the N-efficient D4-15 line compared with the N-inefficient D1-1 at maturity. More exotic genome components were introgressed into the genome of D4-15 (64·97 %) compared with D1-1 (32·23 %).
  
  
  CONCLUSIONS
  The N-efficient new-type B. napus identified in this research had higher N efficiency (and tolerance to low-N stress) than traditional B. napus cultivars, and thus could have important potential for use in breeding N-efficient B. napus cultivars in the field.
authors.affiliation: National Key Laboratory of Crop Genetic Improvement Microelement Research Centre, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Gaili
authors.initials: G
authors.lastname: Wang
authors.affiliation: National Key Laboratory of Crop Genetic Improvement Microelement Research Centre, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Guangda
authors.initials: G
authors.lastname: Ding
authors.affiliation: National Key Laboratory of Crop Genetic Improvement Microelement Research Centre, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.affiliation: Microelement Research Centre, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Cai
authors.affiliation: Microelement Research Centre, Huazhong Agricultural University, Wuhan 430070, China.
authors.forename: Xiangsheng
authors.initials: X
authors.lastname: Ye
authors.affiliation: National Key Laboratory of Crop Genetic Improvement.
authors.forename: Jun
authors.initials: J
authors.lastname: Zou
authors.affiliation: National Key Laboratory of Crop Genetic Improvement Microelement Research Centre, Huazhong Agricultural University, Wuhan 430070, China fangsenxu@mail.hzau.edu.cn.
authors.forename: Fangsen
authors.initials: F
authors.lastname: Xu
mesh_terms: D029688:Brassica napus / Q000235:genetics* / Q000378:metabolism*; D005838:Genotype; D006824:Hybridization, Genetic; D009584:Nitrogen / Q000172:deficiency / Q000378:metabolism*; D036226:Seedlings
chemical_list: D009584:Nitrogen
keywords: 15NH4+; 15NO3− uptake; Brassica napus; New-type; character traits; gene expression; genetic variation; glutamine synthetase; interspecific hybridization; nitrate reductase; nitrogen efficiency; nitrogen transporter