Genomic variation in the hybrids of white crucian carp and red crucian carp: evidence from ribosomal DNA

Abstract

In this study, we conducted a cross of white crucian carp (♀)×red crucian carp (♂) (WR), and characterized the morphology, reproduction and genetics of the progeny. Different from parents, WR with the gray color showed the hybrid morphological traits of both parents. WR possessed normal gonads producing mature eggs or sperm, and exhibited high fertilization rate (90.2%) and high hatchery rate (80.5%), which contributed to produce and enlarge the population. WR with the same DNA content as parents was a diploid fish with 100 chromosomes (2n=100). Amplified ITS of 45S rDNA, in WR the sequences consisting of 884 bp bases of the entire ITS-1 region, 5.8 S region, and entire ITS-2 region. The sequences showed high similarity between WR and its parents and leaned towards male inheritance. In WR, NTS of 5S rDNA consisted of three length types with total 654 bp bases. From sequence analysis of NTS, WR shared 94.2% and 95.1% similarities with their female and male parent, respectively. Sequence analysis of ITS and NTS revealed that there existed recombination and variation in the hybrid progeny, which was the genetic base for adaptation and speciation. In conclusion, we obtained WR from hybridization and it exhibited hybrid traits in morphology and variation in genetic composition showing essential difference with its parents. The obtainment of WR has important significance in fish genetic breeding.white crucian carp, red crucian carp, hybridization, genomic variation Citation:

The chimeric genes in the hybrid lineage of Carassius auratus cuvieri (♀)×Carassius auratus red var. (♂)

“…(Figure 1A and B). One type of F 1 hybrid was obtained in the present study, which was diploid (2n=100), as previously reported (Wang et al, 2015). The diploid hybrid was bisexually fertile showing a normal pattern of gamete development (Figure 1C).…”

“…The diploid hybrid was bisexually fertile showing a normal pattern of gamete development (Figure 1C). Meanwhile, as previously reported (Wang et al, 2015), an F 2 population was created by F 1 self-crossing (Figure 1D).…”

“…White crucian carp (Carassius auratus cuvieri, WCC) and red crucian carp (Carassius auratus red var., RCC) are the members of Cyprinidae (genus Carassius) and have the same number of chromosomes (2n=100). In our previous study (Wang et al, 2015), the crossing of WCC (female) and RCC (male) produced diploid hybrids (WR). These hybrids had a gray color, exhibited hybrid morphological traits which were different from the parents, and showed obvious heterosis; sequence analysis of ribosomal DNA revealed that recombination and variation existed in WR (Wang et al, 2015).…”

“…In our previous study (Wang et al, 2015), the crossing of WCC (female) and RCC (male) produced diploid hybrids (WR). These hybrids had a gray color, exhibited hybrid morphological traits which were different from the parents, and showed obvious heterosis; sequence analysis of ribosomal DNA revealed that recombination and variation existed in WR (Wang et al, 2015).…”

A New Type of Allodiploid Hybrids Derived From Female Megalobrama amblycephala × Male Gobiocypris rarus

“…Distant hybridization is an important technique and widely used in fish genetic breeding, which can combine whole genomes from parent species and lead to changes in both phenotypes and genotypes in the offspring ( Liu, 2010 ; Zhang et al, 2014 ; Xu et al, 2015a ). For example, in terms of phenotypes, the allodiploid lineage with hybrid traits, high survival rate, good meat quality, and strong stress resistance were established by the distant hybridization of Japanese white crucian carp ( Carassius cuvieri , ♀) and red crucian carp ( Carassius auratus red var., ♂) ( Wang et al, 2015 ; Liu et al, 2017 , 2018 , 2019a , b ); the triploid fish with fast growth were produced by the crossing of diploid fish with allotetraploid fish ( Tiwary et al, 2004 ; Zhong et al, 2012 ; Wang et al, 2020 ); in terms of genotypes, a high proportion of chimeric genes (>9%) have been found among orthologous genes in the transcriptomes of allotetraploid fish ( Liu et al, 2016 ); many different expressed genes associated with sperm flagellar assembly and motility were found in testis transcriptomes from diploid fish and triploid fish ( Xu et al, 2015b ; Li et al, 2018a ). These phenotypes and genotypes are very important for breeding applications and scientific research.…”