The formation of diploid and triploid hybrids of female grass carp × male blunt snout bream and their 5S rDNA analysis

Weiguo He,Jie Hu,Lihua Xie,Yun Liu,Jing Wang,Shaojun Liu,Tangluo Li,Jun Xiao,Qinbo Qin

doi:10.1186/1471-2156-14-110

Abstract

BackgroundHybridization 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.ResultsDiploid 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.ConclusionsThis 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.

Highlights

Hybridization is a useful strategy to alter the genotypes and phenotypes of the offspring
The term hybrid can be defined as organisms formed by cross-fertilization between individuals of different species, or it can be applied more broadly to the offspring between individuals from populations which are distinguishable on the basis of one or more heritable characters [1]
Formation of diploid and triploid hybrids The crossing of grass carp (GC)♀ × blunt snout bream (BSB)♂ resulted in a high fertilization rate (95%) and hatching rate (80%) but low adulthood rate (1%)

Summary

Introduction

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. Grass carp have been introduced throughout the world because of their value as a food fish and their ability to control aquatic vegetation. Grass carp grow rapidly compared to other common fish [12,13]. By using GC (Ctenopharyngodon idellus) and BSB (Megalobrama amblycephala), diploid and triploid hybrid fish were successfully produced. It is the first time to obtain the diploid and triploid hybrids by crossing GC and BSB which possess the same chromosome number in vertebrates

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Discussion

Conclusion