Genetic variants of the progesterone receptor (PGR) in the cattle population of the Republic of Tatarstan

The intensification of dairy cattle farming, accompanied by a decline in reproductive functions, requires the implementation of modern genetic selection methods. One promising direction is marker-assisted selection (MAS) using candidate genes associated with reproductive traits. The progesterone receptor gene (PGR), which plays a key role in regulating ovulation, embryo implantation, and pregnancy maintenance, is considered as such a candidate. The aim of this study was to analyze the T81637C (rs41614030) polymorphism of the PGR gene in the cattle population of the Republic of Tatarstan. The study was conducted on two cattle groups: 297 Holstein cows and 67 sires. Genotyping was performed using the PCR-RFLP method with restriction by EcoRV endonuclease. It was found that the cow population is characterized by a significant deviation from the Hardy-Weinberg equilibrium (χ² = 8.52; p < 0.05) with an excess of heterozygotes (CT = 57.3%) and an increased frequency of the C allele (0.572). In contrast, the bull population was in a state of genetic equilibrium (χ² = 0.38) with a distribution of alleles (C = 0.493; T = 0.507) and genotypes (CT = 53.7%; CC = 22.4%; TT = 23.9%). The obtained fixation index values (Fis = -0.169 for cows and -0.075 for bulls) indicate effective breeding work without inbreeding depression. The polymorphism informativeness (PIC = 0.370- 0.375) characterizes the marker as moderately informative. A comparative analysis with data from other studies confirmed the universal nature of the genotype distribution according to the CT > CC > TT scheme in various Holstein cattle populations. The results demonstrate the prospects of using the T81637C polymorphism of the PGR gene in genomic selection programs to improve the reproductive qualities of dairy cattle.