Machmoum, M., Badaoui, B., Petit, D., Germot, A., El Alaoui, M. A., Boujenane, I., et al. (2023). Genetic Diversity and Maternal Phylogenetic Relationships among Populations and Strains of Arabian Show Horses.
Abstract: Genetic diversity and phylogenetic relationships within the Arabian show horse populations are of particular interest to breeders worldwide. Using the complete mitochondrial DNA D-loop sequence (916 pb), this study aimed (i) to understand the genetic relationship between three populations, the Desert-Bred (DB), a subset of the Kingdom of Saudi Arabia (KSA), United Arab Emirates (UAE) and Bahrain (BAH), the Straight Egyptian (EG) and the Polish bloodline (PL), and (ii) to assess the accuracy of the traditional strain classification system based on maternal lines, as stated by the Bedouin culture. To that end, we collected 211 hair samples from stud farms renowned for breeding Arabian show horses from Nejd KSA, Bahrain, Egypt, Qatar, Morocco, UAE, and Poland. The phylogenetic and network analyses of the whole mitochondrial DNA D-loop sequence highlighted a great genetic diversity among the Arabian horse populations, in which about 75% of variance was assigned to populations and 25% to strains. The discriminant analysis of principal components illustrated a relative distinction between those populations. A clear subdivision between traditional strains was found in PL, in contrast to the situation of DB and EG populations. However, several Polish horse individuals could not be traced back to the Bedouin tribes by historical documentation and were shown to differ genetically from other studied Bedouin strains, hence motivating extended investigations.
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Piro, M., Benjouad, A., Karom, A., Nabich, A., Benbihi, N., El Allali, K., et al. (2011). Genetic Structure of Severe Combined Immunodeficiency Carrier Horses in Morocco Inferred by Microsatellite Data. J. Equine Vet. Sci., 31(11), 618–624.
Abstract: A total of 17 microsatellite deoxyribonucleic acid loci used routinely for horse parentage control were used to evaluate genetic diversity among normal Arabian horses and severe combined immunodeficiency (SCID) carrier Arabian horses (ArS) and normal Arab-Barb horses and SCID carrier Arab-Barb horses (ArbeS). On the basis of the genotype of 186 horses, mean allelic diversity was estimated as 6.82, 5.53, and 6.7059 in normal Arabian horses, ArS, and for both groups of Arab-Barb horses, respectively. Five specific alleles were observed in ArS and ArbeS, with one common with ArS at HMS6, whereas five alleles common between ArS and ArbeS had a high frequency. Expected and observed heterozygosity showed great heterogeneity in the population studied and were similar or higher when compared with other studies on Arabian horses. Coefficient of gene differentiation Gst of Nei associated with Nei's genetic distance and multivariate correspondence analysis indicated a possible differentiation between the studied populations when analyzed separately according to breed. Probability of assignment of a horse to a specific group was assessed using a full and partial Bayesian approach. In all, 80.6% of Arab horses and 78.2% of Arab-Barb horses were assigned properly with a partial Bayesian test, which provided better results than the full one. These findings will be useful for identification of SCID carrier horses by using the microsatellite deoxyribonucleic acid loci used routinely for horse parentage control in our laboratory.
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Ishida, N., Oyunsuren, T., Mashima, S., Mukoyama, H., & Saitou, N. (1995). Mitochondrial DNA sequences of various species of the genus Equus with special reference to the phylogenetic relationship between Przewalskii's wild horse and domestic horse. J Mol Evol, 41(2), 180–188.
Abstract: The noncoding region between tRNAPro and the large conserved sequence block is the most variable region in the mammalian mitochondrial DNA D-loop region. This variable region (ca. 270 bp) of four species of Equus, including Mongolian and Japanese native domestic horses as well as Przewalskii's (or Mongolian) wild horse, were sequenced. These data were compared with our recently published Thoroughbred horse mitochondrial DNA sequences. The evolutionary rate of this region among the four species of Equus was estimated to be 2-4 x 10(-8) per site per year. Phylogenetic trees of Equus species demonstrate that Przewalskii's wild horse is within the genetic variation among the domestic horse. This suggests that the chromosome number change (probably increase) of the Przewalskii's wild horse occurred rather recently.
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Oakenfull, E. A., & Ryder, O. A. (1998). Mitochondrial control region and 12S rRNA variation in Przewalski's horse (Equus przewalskii). Anim Genet, 29(6), 456–459.
Abstract: Variation in the control region and the 12S rRNA gene of all surviving mitochondrial lineages of Przewalski's horse was investigated. Variation is low despite the present day population being descended from 13 individuals probably representing animals from three different regions of its range. Phylogenetic comparison of these sequences, with sequences for the domestic horse, does not resolve the ancestral status of either horse.
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Wallner, B., Brem, G., Muller, M., & Achmann, R. (2003). Fixed nucleotide differences on the Y chromosome indicate clear divergence between Equus przewalskii and Equus caballus. Anim Genet, 34(6), 453–456.
Abstract: The phylogenetic relationship between Equus przewalskii and E. caballus is often a matter of debate. Although these taxa have different chromosome numbers, they do not form monophyletic clades in a phylogenetic tree based on mtDNA sequences. Here we report sequence variation from five newly identified Y chromosome regions of the horse. Two fixed nucleotide differences on the Y chromosome clearly display Przewalski's horse and domestic horse as sister taxa. At both positions the Przewalski's horse haplotype shows the ancestral state, in common with the members of the zebra/ass lineage. We discuss the factors that may have led to the differences in mtDNA and Y-chromosomal observations.
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