Study On Genetic Variation Among Different Generations Of Shenxian Pigs

In order to analyze the conservation effect of Shenxian pig population and to provide a theoretical basis for the formulation and adjustment of the conservation scheme of Shenxian pig and its similar local pig population,164 ear tissue samples from 1 ~ 4 generations of Shenxian pig were collected by stratified random sampling.Two sets of genetic materials,mitochondrial genome and nuclear genome,were detected by using 5 rapidly evolving genes in the mitochondrial genome and 27 microsatellite loci in the nuclear genome.The results were as follows:1.The monitoring results of microsatellite molecular markers showed that the average number of effective alleles was between 3.8681 and 4.1910,the average polymorphism information content was between 0.5932 and 0.6545,and the average expected heterozygosity was between 0.6497 and 0.6909,the average fixed index was between 0.5043 and 0.5215.With the replacement of generations,the number of alleles in the four generations increased from generation to generation.During the process of seed preservation,no complete loss of alleles was found in the process of seed preservation,and the PIC value of each generation was higher than 0.5.It can be seen that the whole population shows a high degree of polymorphism.It can be seen that there is no significant difference in the average PIC value between generations,which proves that Shenxian pigs maintain a stable diversity in the process of seed preservation,and although inbreeding occurs in four generations,the degree of inbreeding does not increase.2.A total of 32 haplotypes and 27 variation sites were detected in 4 generations of 5 generations of mtDNA gene in Shenxian pig,of which 6 were converted,11 were subverted,and the number of swinging was significantly higher than that of transformation,which indicated that Shenxian pig population had strong bias.The average haplotype(HD)and(K)of mtDNA genes of generation 1,2,3 and 4 in Shenxian pigs were between 0.3088 and 0.3794,and the average number of nucleotides was between 0.3778 and 0.6467,respectively.The(Pi)of nucleotides diversity was between 0.000306 and 0.000452.Within the group The average haplotype diversity and nucleotides diversity remained stable in four generations.Tajima's D value was used for neutral test in all four generations,and it was not significant,which was consistent with neutral mutation.The results showed that the population size of Shenxian pigs was stable and the genetic diversity was stable during generation transmission.3.The genetic diversity of Shenxian pigs was compared with that of other breeds.Compared with other breeds,the genetic diversity of nuclear genome of Shenxian pigs was rich,but the genetic diversity of mitochondrial DNA was poor.It is proved that Shenxian pig restoration population has good genetic diversity in the initial generation,but the maternal source is narrow.The patrilineal consanguinity is rich and plays an important role in the genetic diversity of the population.In the phylogenetic tree of full sequence NJ of mtDNA CytB gene of Shenxian pig,the three haplotypes of Shenxian pig were clustered into the same branch,and the maternal line was single,which was close to the genetic distance of Shandong breeds such as Laiwu pig and Dapulian pig.From the above results,the following conclusions can be drawn: the results of the two molecular markers show that the population number of Shenxian pigs remains stable and the genetic diversity is at a stable level during the genetic process of generations,and seed conservation has played a good effect.