Evaluation of the genetic diversity of Iranian Arabian horses

Horses (Equus ferus caballus) have always been alongside humans and played an important role in the formation of human civilization. Horses are vertebrates that belong to the Mammalia class, the Equidae family, and the Equus genus. There are free and wild horses in Africa, Asia, Australia, Europe, North and South America, and some oceanic islands. Because of the long-standing relationship with human civilization, horses are considered as companions, a symbol of power and predilection, human assistant, and rival of other animals. The origins of domesticated horses have always been interesting to humans, and studying them is very important. Archaeological evidence and analysis of the horse's body color indicate that the first horses were found in the Eurasian steppes between 5th and 4th millennia BC. Among the genetic studies, simple repeat sequencing can be implied. Random repetitive sequences are scattered throughout the genome and show high polymorphisms that are harbored consecutively and repeat almost every 3-5 Kbp of genome. These sequences comprise a total of 20% of the mammalian genome sequence.

Blood samples were obtained from Arabian horses and their DNAs extracted using salting out method. Extracted DNAs was run in an agarose gel and concentration and quality of DNAs were measured by Nano-drop. Four microsatellite markers were used that all have been recommended by International Society for Animal Genetics (ISAG) for testing the parentship. These markers included ASB17, LEX3, HMS1 and CA425. These loci were amplified by multiplex polymerase chain reaction (PCR) with fluorescent dye-labeled primers. PCR was performed using total volume of 25 ml for each sample and PCR products were separated and analyzed with capillary electrophoresis and the products were evaluated using GenMapper software.

According to the results obtained, the smallest allele was found is 88 bp at the position of ASB17 locus, as expected. Moreover, the largest allele observed in this population was 110 bp. The most frequent allele observed in the population was also 110 bp, with an allele frequency of 0.46%. For LEX3, the smallest allele observed is 144 bp, which was expected. The largest allele observed in this population was 166 bp, which was more than expected range. The most frequent allele observed in the population was 160 bp, with an allele frequency of 0.32%. However, the smallest allele observed in the population at position HMS1 was 172 bp, which was expected to be within the normal allele frequency range. The largest allele observed in the population was 182 bp, which was expected to be in the allele range. The most abundant allele observed in the population was the 174 bp allele, with a frequency of 0.41%, which has a high prevalence in other races. For CA425, the smallest size of the allele observed for this site was in the population of 242 bp, which was smaller than the expected allele size and had a significant frequency of 0.11%. The largest allele size observed in this site was 248 bp, which was expected to be above the expected allele range. The largest allele observed in the population was 182 bp, which was expected to be in the allele range. The most abundant allele observed in the population was the 174 bp allele, with a frequency of 0.41%, which has a high prevalence in other races. For CA425, the smallest size of the allele observed for this site was in the population of 242 bp, which was smaller than the expected allele size and has a significant frequency of 0.11%. The largest allele size observed in this site was 248 bp, which was expected to be higher than the expected allele range.

According to the results obtained from the observed alleles in the studied population of Arabian horses, there is a relatively high genetic variation among this population. It can also be said that for some alleles, there is a high prevalence in the Arabian horse population, while they were not seen in other breeds of horses. In general, several alleles in the Arabian horse population of Iran have been observed with different frequencies that were not present in rest of the races, which implies to the differentiation of this race from horses of other races.