Study On Genetic Diversity Of Chinese Main Indigenous Sheep Breeds

The PCR-RFLP of mitochondria! DNA (mtDNA) dominate region (D-loop) in 10 sheep breeds (8 Chinese indigenous sheep breeds and 2 alien indraught sheep breeds) was studied using 5 restriction endonucleases (Hinf I, Msp I, Xsp I , Sau3A I, Taq I ) with 2 peculiar primers (A:5'-AACTCCCAAACATACAACACGG-3', B:5'-ATTTGAGTATTGAGGGCGGGAT-3'); the genome DNA RAPD of 88 individuals from the same 8 Chinese indigenous sheep breeds was studied too using 10 arbitrary primers with 10 base pairs. The results indicated that: (i) 22 restriction sites and 17 restriction morphs were detected, which could be sorted into 14 haplotypes in all individuals and all restriction endonucleases were polymorphic; (ii) Haplotype A (Hinf I-A, Msp I-A, Sau3A I-A, Xsp I-A, Taq I-A) and haplotype B (Hinf I-A., Msp I-A, Sau3A I-A, Xsp-B, Taq I-A) were the main haplotpyes, the mtDNA D-loop molecular dendrogram among 8 Chinese indigenous sheep breeds was sorted into two groups, the genome DNA molecular dendrogram among them was sorted into two groups too, Tibetan sheep and Mongolia sheep were classified into the two groups respectively, it was concluded preliminary that Chinese domestic sheep derived from two ancestral maternal sources; (iii) The percentage of polymorphic loci and the average index of genetic diversity was 81.36% and 1.3370 respectively, the index of genetic differentiation was 0.9172, it inferred that Chinese indigenous sheep breeds were with abundant genetic diversity and the genetic variation existed mainly between populations; (iv) The dendrogram among Mongolia sheep, Ujumqin sheep, Small Tail Han sheep and Hu sheep indicated that the genetic differentiation among the 4 indigenous sheep breeds with same origination was evident, and the genetic differentiation between Hu sheep and Mongolia sheep was higher than that between Small Tail Han sheep and Ujumqin sheep, but the genetic differentiation between two groups was the highest; (v) Tibetan sheep, Ujumqin sheep and Mongolia sheep were simple in haplotype of mtDNA D-loop, Tan sheep, Small Tail Han sheep Tibetan sheep and Mongolia sheep were with deficient genetic diversity;(vi) Haplotype I (Hinf I -C, Msp I -A, Sau3A I -A, Xsp I -B, Tag I -A) detached 2 alien indraught sheep breeds from 8 Chinese indigenous sheep breeds so evident that haplotype I may be a peculiar haplotype for European sheep breeds; (vii) The mean genetic distance (P) and the average polymorphic degree ( ) of mtDNA D-loop from 10 breeds was 0.0322 and 0.0060% respectively.