title: The formation of diploid and triploid hybrids of female grass carp × male blunt snout bream and their 5S rDNA analysis.
abstract: BACKGROUND
  Hybridization is a useful strategy to alter the genotypes and phenotypes of the offspring. It could transfer the genome of one species to another through combing the different genome of parents in the hybrid offspring. And the offspring may exhibit advantages in growth rate, disease resistance, survival rate and appearance, which resulting from the combination of the beneficial traits from both parents.
  
  
  RESULTS
  Diploid and triploid hybrids of female grass carp (Ctenopharyngodon idellus, GC, Cyprininae, 2n = 48) × male blunt snout bream (Megalobrama amblycephala, BSB, Cultrinae, 2n = 48) were successfully obtained by distant hybridization. Diploid hybrids had 48 chromosomes, with one set from GC and one set from BSB. Triploid hybrids possessed 72 chromosomes, with two sets from GC and one set from BSB.The morphological traits, growth rates, and feeding ecology of the parents and hybrid offspring were compared and analyzed. The two kinds of hybrid offspring exhibited significantly phenotypic divergence from GC and BSB. 2nGB hybrids showed similar growth rate compared to that of GC, and 3nGB hybrids significantly higher results. Furthermore, the feeding ecology of hybrid progeny was omnivorous.The 5S rDNA of GC, BSB and their hybrid offspring were also cloned and sequenced. There was only one type of 5S rDNA (designated type I: 180 bp) in GC and one type of 5S rDNA (designated type II: 188 bp) in BSB. However, in the hybrid progeny, diploid and triploid hybrids both inherited type I and type II from their parents, respectively. In addition, a chimera of type I and type II was observed in the genome of diploid and triploid hybrids, excepting a 10 bp of polyA insertion in type II sequence of the chimera of the diploid hybrids.
  
  
  CONCLUSIONS
  This is the first report of diploid and triploid hybrids being produced by crossing GC and BSB, which have the same chromosome number. The obtainment of two new hybrid offspring has significance in fish genetic breeding. The results illustrate the effect of hybridization and polyploidization on the organization and variation of 5S rDNA in hybrid offspring.
authors.affiliation: Key Laboratory of Protein Chemistry and Fish Developmental Biology of Education Ministry of China, College of Life Sciences, Hunan Normal University, Changsha 410081, P R, China. lsj@hunnu.edu.cn.
authors.forename: Weiguo
authors.initials: W
authors.lastname: He
authors.forename: Lihua
authors.initials: L
authors.lastname: Xie
authors.forename: Tangluo
authors.initials: T
authors.lastname: Li
authors.forename: Shaojun
authors.initials: S
authors.lastname: Liu
authors.forename: Jun
authors.initials: J
authors.lastname: Xiao
authors.forename: Jie
authors.initials: J
authors.lastname: Hu
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Qinbo
authors.initials: Q
authors.lastname: Qin
authors.forename: Yun
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000818:Animals; D001483:Base Sequence; D001947:Breeding; D002347:Carps / Q000235:genetics*; D002875:Chromosomes; D003530:Cyprinidae / Q000235:genetics*; D004275:DNA, Ribosomal / Q000032:analysis; D004171:Diploidy; D005260:Female; D016678:Genome; D006824:Hybridization, Genetic; D007621:Karyotyping; D008297:Male; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D012341:RNA, Ribosomal, 5S / Q000235:genetics*; D017422:Sequence Analysis, DNA; D057885:Triploidy
chemical_list: D004275:DNA, Ribosomal; D012341:RNA, Ribosomal, 5S