Genetic diversity of Cheju horses (Equus caballus) determined by using mitochondrial DNA D-loop polymorphism.

This research article investigates the genetic diversity of horses (Equus caballus) in Cheju, a southern island of Korea, by studying the mitochondrial DNA D-loop polymorphism, finding diverse genetic patterns related to different global horse breeds.

Method and Sample Selection

• The researchers examined the sequence polymorphism of the mitochondrial DNA D-loop, which is a segment of DNA associated with genetic variance in horses.
• The specific length of the DNA sequence used for analysis was 968 base pairs, excluding the tandem repeat region, a region of repetitive DNA sequences.
• The sample consisted of 65 Cheju horse specimens.

Genetic Diversity Analysis

• A total of seventeen different haplotypes or unique DNA groups, varying in frequency from 1.5% to 21.5%, were identified in the Cheju horse samples.
• Overall genetic diversity for the seventeen haplotypes, represented by the variable (h), was calculated to be 0.91. This indicates a wide variety of genetic groups within the maternal lineage of the existing Cheju horse population.

Phylogenetic Analysis

• The researchers performed a phylogenetic analysis, which involves constructing a “family tree” of sorts to determine the relations between different species or groups based on their characteristics (in this case, D-loop sequences).
• This analysis involved not just the Cheju horses, but also sequences from different horse breeds worldwide, including Mongolian, Arabian, Belgian, Tsushima, Yunnan, Przewalskii, and Thoroughbred horses.
• The results showed that the Cheju horses were distributed across many different clusters on the phylogenetic tree, suggesting diverse origins.
• Four Mongolian horses grouped with separate Cheju horse groups, suggesting there were cases where Cheju horses were clearly of Mongolian origin.

Conclusion

• The researchers found that global horse breeds such as the Thoroughbred, Mongolian, Lipizzan, and Arabian demonstrate genetic diversity on par with the Cheju horses, according to partial sequences (284 base pairs) of the D-loop from 109 horses.
• The study concludes that most horse breeds tested with a sufficient number of samples demonstrate significant diversity in their maternal lineages, with none of the breeds being unique or significantly different from the others.