A Genome-Wide Scan for Signatures of Selection in Kurdish Horse Breed.

This research study used genetic typing to identify areas of the genome that have been under selection in the Kurdish horse population, helping to uncover their genetic diversity and probable past inbreeding.

Objective and Methodology

• The study aimed to understand the genetic diversity and to identify the genomic regions that have been under putative natural selection in the Kurdish horse population.
• To accomplish this, the researchers sampled and genotyped 72 horses using a GGP Equine 70K SNP array (which checks for specific genetic variations known as Single Nucleotide Polymorphisms).

Findings on Genetic Diversity and Inbreeding

• Analyses suggested a sharp decline in effective population size (Ne), a measure of genetic diversity, occurred about four generations ago.
• There was also a high frequency of runs of homozygosity (ROH) in length of 2-4 Mbp, suggesting inbreeding likely occurred around 20 generations ago.
• The effective population size was found to be 104 horses up to three generations ago.
• The average inbreeding (F) was calculated to be 0.047(± 0.045), providing another confirmation of the historical inbreeding.

Signatures of Selection

• Using techniques such as de-correlated composite of multiple selection signals (DCMS) and runs of homozygosity (ROH) analyses, the researchers identified genomic regions under putative selection.
• A total of 148 significant SNPs were discovered through DCMS, 40% of which were located on the equine chromosome ECA9.
• This region is known to contain Quantitative Trait Loci (QTL), or areas of the genome that are associated with differences in traits like body size.
• Other regions significantly associated with traits such as insect bite hypersensitivity (IBH), hair density and coat texture, alternate gaits, guttural pouch tympany and temperament were also identified.
• Additionally, two hotspot regions were identified on ECA7 and ECA11, which also host QTL associated with withers height, alternate gait and IBH when using outputs of ROH analyses.

Final Summary and Suggestion for Future Research

• Overall, the research resulted in the identification of genomic regions under possible natural selection, hosting known QTL associated with traits such as body size and IBH amongst others.
• While these findings contribute towards understanding the genetic makeup and history of the Kurdish horse population, the researchers emphasize that further functional and comparative studies are necessary to solidify these findings and to better understand their impact on the genetic and phenotypic diversity of these horses.