Genetic relationships of seven horse breeds in South Africa based on DNA markers

[摘要] English: The story of the horse begins nearly 60 million years ago. Herds of horses were initially a source of food for humans. Between 5 000 - 6 000 years ago on the Eurasian steppes, nomadic Aryan people began the process of domesticating the horse. Domestication resulted in different breeds, which served a variety of purposes. Horses are now mainly used for pleasure and sport of which there are many different varieties. Genetic characterization is the first step in breed conservation and may have implication for future breeding strategies. The genetic diversity of domestic species such as cattle, sheep and goats has been examined by microsatellite analysis. More recently, horse breeds have also been analyzed using a panel of microsatellites recommended for routine parentage testing. The aim of this study was to determine whether the horse breeds in South Africa is being kept pure and whether there is still enough genetic variation in the different horse breeds. It was also my aim to determine whether the Cape horse has genetically evolved far enough from the S.A. Boerperd to be classified as a horse breed that was bred in South Africa. All the horse populations were in Hardy-Weinberg equilibrium except for the S.A. Boerperd. The Chi-square test showed that the S.A. Boerperd was not in Hardy-Weinberg equilibrium, but the G-test showed otherwise. Studies by Dr. E. van Dyk (Faculty of Veterinary Science at the University of Pretoria, South Africa) indicated that there has been more outbreeding of Boerperde than the other horse breeds and that they are the least closely related to one another than the other horse breeds. The S.A Boerperd and the Welsh ponies display the greatest degree of heterozygosity (genetic variation between individuals). Which suggests that there has been more outbreeding of Boerperde and that the breed has not been a closed herd, as closed herds tend to become more homozygous over such a long period of time. These results support results given by Dr. Evan Dyk done with bloodtyping. The highest average frequency for an allele is for HTG7. Other alleles had an average of 0.114. It is of great importance, because these microsatellites are used for determining parentage. If the frequency of an allele becomes to high, it cannot be use to distinguished between two individuals. Relatively small differentiation values were observed for the American Saddler and the S.A. Boerperd and between the Boerperd and the Cape horse. The most distinct difference was observed between the Friesian horse and the Cape horse. The dendrograms showed that the S.A. Boerperd and the Cape horse are very closely related. The Friesian is the least related of all the horse breeds, except for the Przewalski horse. These results correspond with those find by E van Dyk and with the history of the different breeds. This thesis is a contribution to the FAO and their global programme as well as to all horse breeders in South Africa.

[发布机构] University of the Free State