Genetic Diversity and Structure of Iranian Horses’ Population Based on Mitochondrial Markers.

The research aimed to investigate the genetic structure and relationships between six breeds of native Iranian horses using markers found in their mitochondrial D-Loop region, revealing a high level of genetic diversity and numerous maternal lines.

Genetic Analysis of Iranian Horses

• The researchers collected blood samples from 96 horses representing six particular Iranian horse breeds.
• The DNA was extracted from these blood samples, and a specific section (known as the D-Loop region) of the mitochondrial DNA, which is highly variable, was amplified and sequenced using the Sanger sequencing technique. Amplification and sequencing are common methods used in genetic research to reveal the specific makeup of a segment of DNA.
• The genetic data were analysed to identify polymorphic sites which are locations of DNA sequences which differed between individuals.
• The analysis identified 48 polymorphic sites, which led to the classification of the horses into 52 different haplotypes. A haplotype is a set of genes within an organism that was inherited together from a single parent, so this result indicates a high level of genetic diversity within the group of horses studied.

Phylogenetic Tree and Haplogroups

• These haplotypes were used to create a phylogenetic tree. This is a diagram that scientists use to depict the evolutionary relationships between different species or groups, based on their genetic similarities and differences, tracing back to their common ancestral roots. In this case, the resulting tree placed the Iranian horses in 11 distinct ‘haplogroups’ (clusters of similar haplotypes), labelled A through Q.

Genetic Diversity and Differentiation

• The values for genetic diversity observed within the horse population were 0.0233, a figure that indicates a high level of genetic variation within the population. The haplotype diversity, which provides a measure of the uniqueness of a particular gene variant in a population, was 0.980, again indicating high diversity.
• Nucleotide diversity, another measure of genetic variation within a population, ranged from 0.0172 to 0.0242 among the different breeds of horses.
• The study also assessed genetic differentiation by calculating a statistic (Fst) that quantifies the genetic resemblance between populations. The higher this value, the more distinct the groups are genetically. The most substantial difference was detected between Kord horse (KOH) and Darehshori or Qashqai horse (DAH) breeds.

Tajima’s D Test Observation

• The researchers conducted a Tajima’s D test, which is a test for selective neutrality. With a value of 0.441 and significance (P) greater than 0.01, the results of this test were not significant, meaning the results do not suggest evidence of selection processes (i.e., evolutionary pressures shaping the horse’s genetic makeup) in these horse populations.

Conclusions

• The study concludes by highlighting a high degree of genetic diversity and numerous maternal lines in native Iranian horses. This discovery suggests a rich and complex history of horse domestication and breeding in Iran.