Bulgarian Journal of Agricultural Science
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Genetic diversity and population structure of Bulgarian autochthonous sheep breeds based on nucleotide variation in Alpha S1- casein gene
Deyana Gencheva, Svetlana Georgieva
Abstract: The genetic diversity, population structure and relationships of Bulgarian autochthonous sheep breeds were investigated based on nucleotide variation in exon III of the alpha S1- casein (CSN1S1) gene. Two genetic variants of the CSN1S1 gene (A and C) and two genotypes (AC and CC) have been identified using PCR-RFLP analysis on a total of 213 unrelated individuals representing five local sheep breeds: Breznik (BRNK), Copper-red Shumen (CRSH), Karakachan (KKCH), Pleven blackhead (PLBH) and Stara Zagora (STZG), reared in different private sheep-farms under the control of the Executive Agency on Selection and Animal Breeding in Bulgaria. As expected, a 306 bp fragment of the polymorphic locus in CSN1S1 gene was amplified and digested with endonuclease enzyme MboII. The allele frequencies determined a prevalence of the allele C (0.983) over the allele A (0.017) in the studied sheep populations. The obtained restriction fragments revealed two genotypes: AC and CC, observed in 3.4 and 96.6% respectively in the studied sheep populations. The homozygous genotype AA was not identified in the studied sheep breeds. All examined breeds indicated a low level of genetic diversity, with an average of 0.033. The CSN1S1 locus was monomorphic in the population STZG. The estimated negative values of the coefficient Fis (-0.017) showed a low level of inbreeding in all five sheep groups. The exact P-value (P > 0.9) for the separate breeds was established and all sheep breeds were in correspondence with HWE equilibrium at the degree of freedom df = 1. The obtained genetic differentiation between the examined sheep populations was not significant and genetic distances were relatively low. The greatest distance (DA = 0.004) was found between STZG population and CRSH, also between STZG and KKCH, while the closest relationship was established (DA = 0.000) between CRSH, KKCH and BRSK. The Nei’s genetic distances calculated by UPGMA method produced a phylogenetic tree that separates the investigated sheep breeds into two main clusters: one including STZG and PLBH, and the other one consisting of the three remaining sheep breeds – BRSK, CRSH and KKCH. The data obtained in the present study can contribute to developing an effective conservation strategy for traditional sheep breeds in Bulgaria.
Keywords: autochthonous sheep; casein gene; CSN1S1; genetic diversity, PCR-RFLP; Ovis aries, alpha S1
Date published: 2019-12-30
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