Genetic polymorphism at the β-lactoglobulin (β-LG) loci in indigenous sheep breeds (Tsigai, Racka, Pramenka) was determined. Altogether 904 sheep were genotyped for the presence of the A, B and C alleles of β-lactoglobulin by PCR-RFLP. The AB genotype was the most common and the β-lactoglobulin A was the most frequent in the Cokanski Tsigai (54%), while the B allele was the most common in the Rusty and the Zomborski Tsigai (59%, 60%). The C allele was found only in one individual from Serbian Cokanski flock. These results differ from those that refer to other native sheep breeds. In the Cokanski Tsigai, deviation from the Hardy-Weinberg equilibrium was detected. Genetic relationship based on β-lactoglobulin polymorphism was the closest between the Rusty and the Cokanski Tsigai among the studied populations and between sheep and goat among the other ruminants. Part of the promoter region (254 bp) of β-LG in studied sheep breeds were sequenced in order to identify polymorphisms, analyze haplotypes, and phylogenetic relationship among them. Sequencing analysis and alignment of the obtained sequences showed one haplotype. Analysis of more samples and longer parts of the promoter region of β-LG are needed to reconstruct a phylogenetic tree.

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