Genetic diversity and population structure of Bulgarian autochthonous sheep breeds based on nucleotide variation in Alpha S1- casein gene

Deyana Gencheva, Svetlana Georgieva
Trakia University, Faculty of Agriculture, Department of Genetics, Breeding and Reproduction, Students town, Stara Zagora 6000, Bulgaria


Gencheva, D. & Georgieva, S. (2019). Genetic diversity and population structure of Bulgarian autochthonous sheep breeds based on nucleotide variation in Alpha S1- casein gene. Bulg. J. Agric. Sci., 25 (Suppl. 3), 95–102

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; Ovis aries, alpha S1; casein gene; CSN1S1; genetic diversity, PCR-RFLP

See the article as a PDF.