Genetic Variability of Small Horse Populations from Greek Islands

In this study, we analyzed microsatellite variation in DNA obtained from hair samples collected from 46 local Greek horse populations originating from the islands of Skyros (Skyros Small Horse; n=9), Rhodes (Rodos Small Horse; n=6), Lesvos (with the traditional miniature Midili Small Horse (n=2) and the larger Lesvos Gaiter (n=22)) and Crete (Messara) (n=7). We used 15 autosomal microsatellite markers (VHL20, HTG4, AHT4, HMS7, HTG6, AHT5, HMS6, ASB2, HTG10, HTG7, HMS3, HMS2, ASB17, ASB23 and LEX33) for the genetic characterization of the above populations and exploration of their genetic structure and diversity levels. A total of 120 alleles were detected across the 15 loci with a minimum of 4 alleles in HTG7 locus and a maximum of 13 alleles in ASB17 locus. Τhe total per population number of alleles was 42 (Skyros Small Horse), 20 (Rodos Small Horse), 71 (Lesvos Gaiter), 52 (Messara breed) and 21 (Midili Small Horse). The effective number of alleles (Ne) per locus ranged from 1.47±0.13 (Rodos Small Horse) to 4.67±0.31 (Lesvos Gaiter). The allelic richness (Ar) was between 1.50±0.12 (Rodos Small Horse) and 2.93±0.08 (Lesvos Gaiter) and the average Polymorphism Information Content (PIC) values varied from 0.200±0.035 (Rodos Small Horse) to 0.733±0.026 (Lesvos Gaiter). No significant deviations from H-W equilibrium were found except for three loci (ASB2, HTG10 and LEX33) in Messara and one locus (ASB23) in Lesvos Gaiter. Τhe inbreeding coefficient (Fis) ranged from -0.130 (Rodos Small Horse) to 0.042 (Lesvos Gaiter). The observed (Ho) and expected (He) multilocus heterozygosity mean estimations were highest in Lesvos Gaiter (0.764±0.027 and 0.783±0.024, respectively) and smallest in Rodos Small Horse (0.300±0.075 and 0.269±0.064, respectively). Across loci, the total genetic diversity HT was 0.741, the diversity among subpopulations HS was 0.621 and the multilocus genetic differentiation GST was 0.161, which was rather high. The population of Rodos Small Horse separated from the remaining horses as shown by factorial correspondence analysis, population assignment and metric multidimensional scaling diagrams. This study highlights the loss of genetic diversity in small isolated horse populations and the urgent need to take protective measures to preserve them.

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