Abstract
BackgroundThe establishment of the bisexual fertile fish hybrid lineage including the allodiploid and allotetraploid hybrids, from interspecific hybridization of red crucian carp (Carassius auratus red var. 2n = 100, 2n = AA) (♀) × common carp (Cyprinus carpio L. 2n = 100, 2n = BB) (♂), provided a good platform to investigate genetic relationship between the parents and their hybrid progenies.ResultsThe chromosomal inheritance of diploid and allotetraploid hybrid progenies in successive generations, was studied by applying 5S rDNA fluorescence in situ hybridization. Signals of 5S rDNA distinguished the chromosomal constitution of common carp (B-genome) from red crucian carp (A-genome), in which two strong signals were observed on the first submetacentric chromosome, while no major signal was found in common carp. After fish hybridization, one strong signal of 5S rDNA was detected in the same locus on the chromosome of diploid hybrids. As expected, two strong signals were observed in 4nF3 tetraploid hybrids offspring and it is worth mentioning that two strong signals were detected in a separating bivalent of a primary spermatocyte in 4nF3. Furthermore, the mitosis of heterozygous chromosomes was shown normal and stable with blastular tissue histological studies.ConclusionsWe revealed that 5S rDNA signal can be applied to discern A-genome from B-genome, and that 5S rDNA bearing chromosomes can be stably passed down in successive generations. Our work provided a significant method in fish breeding and this is important for studies in fish evolutionary biology.
Highlights
The establishment of the bisexual fertile fish hybrid lineage including the allodiploid and allotetraploid hybrids, from interspecific hybridization of red crucian carp (Carassius auratus red var. 2n = 100, 2n = AA) (♀) × common carp (Cyprinus carpio L. 2n = 100, 2n = BB) (♂), provided a good platform to investigate genetic relationship between the parents and their hybrid progenies
Through selecting and breeding for more than 20 years, the bisexual fertile allotetraploid hybrid fish (4n = 200) has been acquired, which resulted from fertilization of unreduced eggs and sperm produced by hybrids of red crucian carp (Carassius auratus red var. 2n = 100) (♀) × common carp (Cyprinus carpio L. 2n = 100) (♂)
Analysis of 5S rDNA fragments The electrophoretic band pattern of DNA fragments amplified with the primers of 5 s rDNA was distinctive between Red crucian carp (RCC) and Common carp (CC)
Summary
Through selecting and breeding for more than 20 years, the bisexual fertile allotetraploid hybrid fish (abbreviated as AT) (4n = 200) has been acquired, which resulted from fertilization of unreduced eggs and sperm produced by hybrids of red crucian carp The males and females of diploid F2 hybrids could generate unreduced diploid eggs and diploid sperm, respectively, which were fertilized to form the allotetraploid hybrids in F3 fish (abbreviated as 4nF3). Fertile tetraploid female and male F3 fish were found to generate diploid eggs and sperm, respectively.
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