Background: The Akhal-Teke horse (AKH) is native of the modern Turkmenistan area. It was introduced in Italy from 1991 to 2000 mainly as an endurance horse. This paper characterizes the genetic variability of the whole Italian AKH horse population and evaluates their inbreeding level by analyzing microsatellite markers and mitochondrial D-Loop sequences.
Methods: Seventeen microsatellite marker loci were genotyped on 95 DNA samples from almost all the AKH horses bred in Italy in the last 20 years. Standard genetic variability measures (Ho, He, FIS) were compared against the same variables published on other eight AKH populations. In addition, 397 bp of mtDNA D-loop region were sequenced on a sub-group of 22 unrelated AKH out of the 95 sampled ones, and on 11 unrelated Arab horses. The haplotypes identified in the Italian population were aligned to sequences of AKH (56), Arab (five), Caspian Pony (13), Przewalskii (two) and Barb (15) horses available in GenBank. The Median Joining Network (MJN), Principal Component Analysis (PCA) and Neighbor-joining (NJ) tree were calculated on the total 126 sequences.
Results: Nucleic markers showed a high degree of polymorphism (Ho = 0.642; He = 0.649) and a low inbreeding level (FIS = 0.016) in Italian horses, compared to other AKH populations (ranged from -0.103 AKH from Estonia to 0.114 AKH from Czech Republic). High variability was also recorded in the D-Loop region. 11 haplotypes were identified with haplotype diversity (hd), nucleotide diversity (π) and average number of nucleotide differences (k) of 0.938, 0.021 and 6.448, respectively. When all the 126 D-Loop sequences were compared, 51 haplotypes were found, and four were here found only in the Italian AKH horses. The 51 haplotypes were conformed to eight recognized mtDNA haplogroups (A, C, F, G, L, M, P and Q) and confirmed by MJN analysis, Italian horses being assigned to five haplogroups (A, C, G, L and M). Using a PCA approach to the same data, the total haplotypes were grouped into two clusters including A+C+M+P and G+F haplogroups, while L and Q haplogroups remained ungrouped. Finally, the NJ algorithm effectively discretizes only the L haplogroup. All the above data univocally indicate good genetic variability and accurate management of the Akhal-Teke population in Italy.
Keywords: Akhal-Teke; Biodiversity; Genetic variability; Horse; Median joining network; Microsatellite markers; Neighbor-joining tree; PCA; Sequencing; mtDNA D-loop.