Microsatellite Analyses Of Genomic Studies On Artifical Gynogenetic Grass Carp And Wild Grass Carp

Microsatellite primers which can be used for genomic analysis of grass carp were screened from 28 pairs of common carp microsatellite primers with methods of polymerase chain reaction (PCR) and polyacrylamide gel electrophoresis(PAGE). Then these primers were employed to investigate the genetic diversity of wild grass carp population of Xiang-jiang River and the mitogynogenetic grass carp groups induced by the heat-shocking of eggs.The main results and conclusions were as follows:(1) On the optimized conditions of PCR, total 7 out of 28 (about 25%) pairs of primers of common carp microsatellite loci were proved to be able to amplify successfully with model DNA of grass carp and showed clear and specific bands in PAG repeatedly. And 4 pairs of primers (about 14%) showed the polymorphic in population of the wild grass carp. These results indicated that some microsatellite primers developed from common carp could be applied to analyze the genome of grass carp.(2) The average allele numbers (N) were 2 in the wild grass carp population of Xiang-jiang River at 7 microsatellite loci. The average observation heterozygosity (H0) was 0.3571. The average expectation heterozygosity (He) was 0.2992.The effective allele number (Ne) was 1.6791. And the genetic similarity was 0.8043. These results indicated that the genetic diversity in wild grass carp population of Xiang-jiang River was poor.(3) At five out of seven (about 71.4%) microsatellite loci, all 13 individuals of grass carps of the two gynogentic populations (A and B) were homozygous. And at one locus (about 14.3%), some fish have showed homozygous and some heterozygous. These results showed that there was a high proportion of homozygous microsatellite loci in the gynogenetic grass carps. It was surprising that two PCR products wereobserved in all of the 13 individuals of two gynogenetic grass carp groups when their genomic DNA were amplified using the primer MFW1. It was presumed that there were two copies of this microsatellite sequence in the genome of the grass carp, which was needed to test in further studies.(4) Five microsatellite loci of the gynogenetic grass carp population A and four of the population B was genetically homogenous, meaning that each individual in the population had the same genotype at these loci. The genetic similarity index in the gynogenetic grass carp population A and B were 0.9091 and 0.8699 respectively. From these results a conclusion could be made that there was high genetic homozygosity in the two gynogenetic populations.(5) The genetic distance between the wild and gynogenetic grass carp population A was 0.1620 and that between the wild and gynogenetic grass carp population B was 0.1621. It seemed that there were some variations between the gynogenetic and wild populations. But the fact that no significant difference has been detected on the frequencies distribution of alleles of every microsatellite locus among the three populations by t-test indicated that the level of differentiation between the wild and gynogenetic grass carp populations was low since the variation was mainly caused by rare alleles. However, the lost of rare alleles in two populations of the gynogenetic grass carp should be considered in genetic breeding.