Genetic diversity in German draught horse breeds compared with a group of primitive, riding and wild horses by means of microsatellite DNA markers.

We compared the genetic diversity and distance among six German draught horse breeds to wild (Przewalski's Horse), primitive (Icelandic Horse, Sorraia Horse, Exmoor Pony) or riding horse breeds (Hanoverian Warmblood, Arabian) by means of genotypic information from 30 microsatellite loci. The draught horse breeds included the South German Coldblood, Rhenish German Draught Horse, Mecklenburg Coldblood, Saxon Thuringa Coldblood, Black Forest Horse and Schleswig Draught Horse. Despite large differences in population sizes, the average observed heterozygosity (H(o)) differed little among the heavy horse breeds (0.64-0.71), but was considerably lower than in the Hanoverian Warmblood or Icelandic Horse population. The mean number of alleles (N(A)) decreased more markedly with declining population sizes of German draught horse breeds (5.2-6.3) but did not reach the values of Hanoverian Warmblood (N(A) = 6.7). The coefficient of differentiation among the heavy horse breeds showed 11.6% of the diversity between the heavy horse breeds, as opposed to 21.2% between the other horse populations. The differentiation test revealed highly significant genetic differences among all draught horse breeds except the Mecklenburg and Saxon Thuringa Coldbloods. The Schleswig Draught Horse was the most distinct draught horse breed. In conclusion, the study demonstrated a clear distinction among the German draught horse breeds and even among breeds with a very short history of divergence like Rhenish German Draught Horse and its East German subpopulations Mecklenburg and Saxon Thuringa Coldblood.