Study On The Formation And Genetic Traits Of Distant Hybridization Progeny Of Female Carassius Auratus Red Var.× Male Gobiocypris Rarus

Hybridization is an important technique and is widely used in fish genetic breeding.Hybridization can combine whole genomes from parent species,which may lead to changes in both genotype and phenotype in the offspring.Usually,distant hybridization is often accompanied by the appearance of polyploid.In this study,the hybrid progeny(RR)was obtained by distant hybridization derived from the female Carassius auratus red var.(2n=100,RCC)and the Male Gobiocypris rarus(2n=50,RM).The genetic characteristics and biological characteristics of RR and its parents were studied in our research.The major results were presented as following:1.During the incubation period,the fertilization rate and incubation rate of the embryo were calculated.The results showed that the RR had a lower fertility rate(50.3%)and lower incubation rate(20.7%).We investigated the ploidy and chromosomal numbers of RR by the preparation of chromosome by caudal fin cell culture and blood cell DNA content detection.The results showed that RR was a triploid hybrid fish with 125 chromosomes.2.The morphological characteristics of RR and its parents were analyzed.The results showed that: the color of RR was the same as that of its female RCC,but was different from its male RM of silvery white.In countable traits,the numbers of anal fin rays of RR were between from its parents,which reflected the characteristics of hybridization.In measurable traits,except total length/body length,the proportion of other traits of RR was significantly different from that of its parents(P < 0.05).The body length/head length,the value of RR was larger than that of RCC;and the head length/head height,the value of RR was smaller than that of RCC,which suggested that the head of RR was smaller than that of RCC.Histological sectioning was used to examine gonad development in RR.The ovaries of female RR contain oocytes of different phases,and the structure of ovaries develops normally.There were sperm cells in the testis of male RR.3.The sequence of 5S rDNA of RR and its parents was amplified by PCR.The sequence structure and genetic variation of 5S rDNA were systematically analyzed.Three 5S rDNA bands were found in the genomic DNA of RCC by PCR amplification,which were 203 bp,340 bp and 477 bp in size.Two 5S rDNA bands,223 bp in size and 440 bp in size,were found in the genomic DNA amplification of RM.Three 5S rDNA bands,226 bp,340 bp and 477 bp,were also found in the genome amplification of RR.Through sequence alignment analysis,the 226 bp sequence of RR was similar to that of RM,and the 340 bp and 477 bp sequence were similar to that of RCC.The results showed that the 5S rDNA of hybrid offspring of RR inherited not only the specific bands of RCC,but also inherited the specific bands of RM,reflecting its hybridization characteristics.4.The full length of the mitochondrial genome of RR was amplified by PCR,and the amplified sequence was spliced,sequential structure and evolutionary tree were analyzed.The results showed that the total length of the mitochondrion was 16590 bp.The mitochondrial genome of RR consists of 2 r RNA genes,13 protein-coding genes,22 t RNA genes and 2non-coding regions(control region and light chain replication initiation region).The AT content in the mitochondrial genome sequence of RR was higher than that of GC,and there were AT repeats in the D-loop region.The similarity of the mitochondrial genome between RR and female RCC was 99.4%,and that between RR and male RM was 82.1%;and RR mitochondrial genome was more biased toward RCC by the analysis of the mitochondrial phylogenetic tree.So the mitochondrial genome follows the characteristics of maternal inheritance.5.In this study,the expression of IGF-1 and GHR2 genes in liver tissues of RR,RCC and RM were detected by q-PCR.The results showed that IGF-1 and GHR2 genes were expressed in RCC,RM and RR;and the expression of IGF-1 and GHR2 genes in RR was higher than that in its parents.A new triploid hybrid fish with 125 chromosomes was obtained by distant hybridization.And it exhibited heritability and variability at both the shape and molecular levels.The hybrid progeny provides a new experimental material for fish genetic breeding research.