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

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.