Studies On The Molecular Biological Characteristics Of The Polyploidy Hybrids Of Red Crucian Carp(Carassius Auratus Red Var.)((?))×Blunt Snout Bream (Megalobrama Amblycephala)((?))

Distant hybridization refers to the process of combining different varieties of organisms. It is an effective way in genetic breeding, which can change the genetic composition and features of the hybrids, or make the hybrid offspring chromosome level changes and the formation of diploid, triploid or tetraploid offspring. Through distant hybridization, bisexual gynogenetic red crucian carps(2n=100), triploid hybrids(3n=124) and tetraploid hybrids(4n=148) of red crucian carp (Carassius auratus red var.,♀)×blunt snout bream (Megalobrama amblycephala)(♂) were produced successfully. In addition, studies of these different ploidy-level hybrid offspring on genetic composition, genetic variation and characteristics of reproductive were performed, and the detail contents show as follows:1. We used specific repetitive sequence of red crucian carp (JQ086761) as a fluorescent probe to identited the ploidy-level between hybrids and their parents showed that the bisexual gynogenetic red crucian carps possessed two sets of RCC-derived chromosomes. The triploid hybrids possessed two sets of RCC-derived chromosomes and one set of BSB-derived chromosome. There are100sources in the red crucian carp124chromosomes of the triploid hybrids. The tetraploid hybrids were possessed two sets of RCC-derived chromosomes and two sets of BSB-derived chromosome. There are100sources in the red crucian carp148chromosomes of the tetraploid hybrids. This study demonstrated genetic composition of F1hybrid offspring. The variation of5S rDNA and location on the chromosome of different ploidy hybrid offspring were obtained.2. We used5SrDNA340bp sequence of red crucian carp (GQ485556) as a fluorescent probe to identited the ploidy-level between hybrids and their parents showed that in the red crucian carp (2n=100) can be seen four signals on chromosome, the two intensity signal and two weak signal, but no signal in blunt snout bream; Tetraploid hybrids possessed two sets of RCC-derived chromosomes. The FISH probe in tetraploid hybrids and triploid hybrids exhibited two intensity signals and two weak signals. The bisexual gynogenetic red crucian carps possessed two sets of RCC-derived chromosomes. The bisexual gynogenetic red crucian carps can be seen one intensity signal and two weak signals on chromosome, there one strong signal was lost. This shows that5S rDNA sites in bisexual gynogenetic red crucian carps appeared obvious recombinant progeny.3. The abnormal phenomenon of chromosome during meiosis occurs in the tetraploid hybrids (abbreviated as4nRB,4n=148, AABB) of red crucian carp (abbreviated as RCC,2n=100, AA)(♀)×blunt snout bream (abbreviated as BSB,2n=48, BB)(♂), which give rise to formation of gamete with different size. To test genetic composition of the gamete, we produced gynogenesis offspring without the treatment for doubling the chromosomes of4nRB. Furthermore, their genetic composition was also analyzed. Our results provide that4nRB can produce many gamete with different genetic composition, including allotetraploid gamete (AABB), autotriploid gamete (AAA), autodiploid gamete (AA) This paper detailed reports the abnormal chromosome behavior during meiosis in allotetraploid fish. The present results are of importance in both cytogenetics and evolution.