Polymorphism of Old Kladruber horses, a surviving but endangered baroque breed.

Analysis of MHC class I and class II polymorphism, as well as data from other polymorphic systems (non-MHC lymphocyte alloantigen, blood groups systems, biochemical polymorphisms and microsatellite loci), was used to characterize the extent and distribution of the genic polymorphism of Kladruber horses. A breed-characteristic distribution of the MHC polymorphism was found. The repertoire of defined MHC class I specificities was restricted, especially in the grey subpopulation and in stallions, but a high frequency of blanks suggests the possible existence of undetected specificities. Despite the small population size and a relatively high degree of inbreeding, high heterozygosity in MHC haplotypes has been conserved. The extent of polymorphism and the degree of heterozygosity in other loci were also relatively high. A comparison of the two existing subpopulations, grey and black, at all the loci tested, including RAPD markers, characterized them as genetically distinct, although clearly related. The genetic distances between them were of the same order of magnitude as between distinct breeds. The results may be useful in defining short-term and long-term breeding policy within the breed and for further studies of associations with disease and other traits.