Genetic characterization of Southern African sheep breeds using DNA markers
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Merino sheep are an important resource for South Afric an farmers, providing meat and wool and thus an important income source. Indigenous and locally developed breeds are an important asset for many reasons, but particularly because, over time, they have developed unique combinations of adaptive traits to respond to the pressures of the local environment. To be able to distinguish between breeds for conservation and utilization purposes, the genetic variability, population structure and phylogenetic relationships were determined. Seven different Merino genotypes were sampled. These included the Dormer, SA Merino, SA Mutton Merino, Landsheep, Letelle, Dohne and Afrino. The indigenous and locally developed breeds comprised of the Damara, Pedi, Blinkhaar Ronderib Afrikaner, Blackhead Persian, Blackhead Speckled Persian, Redhead Persian, Redhead Speckled Persian, Zulu, Namaqua Afrikaner, Karakul, Swazi, Van Rooy and Dorper. The Merino, indigenous and locally developed breeds were assessed for genetic diversity using 24 microsatellites. Different statistical analyses were performed to determine the genetic variation, genetic relationships and genetic differentiation of the breeds. The SA Merino showed a high number of very distinct alleles. This study confirmed a higher variability of the SA Merino when compared with the other breeds. The genetic distance between the SA Merino and SA Mutton Merino, both fine wool breeds, was high indicating that these two breeds are relatively distant from each other. The Afrino known to have 25% SA Merino, 25% Ronderib Afrikaner and 50% SA Mutton Merino, indicated a closer relationship with the SA Mutton Merino. This result confirmed the development of the breed. From the phylogenetic analysis between the seven Merino genotypes, when compared to the other estimates obtained in the study, it was evident that the Merino genotypes in South Africa have more within breed variation than between breed variation. The genetic distance estimates observed for the indigenous fat-tailed breeds were relatively high indicating that even between these breeds genetic differences exist. As expected, a smaller genetic distance between the Persian varieties was observed. Genetic distances between the developed breeds supported their ancestral development. The results of the indigenous and locally developed breeds present the first study of the genetic characterization of these breeds using microsatellite markers in South Africa. Southern Africa is hosting a very large sheep (Merino, indigenous and locally developed) genetic resource. Adapted to the agricultural production systems of the continent, it represents a unique resource that has great potential for further development of its productivity.