Balancing selection in Polish Arabian horses

Polish Arabian horses are a good example of a small population derived from a finite number of founders. Pedigree analysis showed significant reduction in the genetic diversity of the population. However, taking into account some circumstances suggesting the presence of balancing selection favouring heterozygotes in Polish breeding, it seems that this referred to pedigree uniformity rather than to a real decrease in genetic variability. The aim of the current study was to verify the hypothesis that balancing selection affects the population. The mare selection process was examined in detail regarding the polymorphism of 10 protein markers. The findings confirmed the tendency to favour the more heterozygous mares with regard to average heterozygosity in total and in relation to particular loci, studs, fathers and inbreeding ranges. The results were discussed in consideration of selection criteria, inbreeding level of Polish Arabs and heterozygosity in other populations.