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University of Zululand (2018)

Genetic variation among Zulu sheep sub-populations of South Africa assessed by microsatellites and mitochondrial DNA (mtDNA)

Selepe, Mokhethi Matthews

Titre : Genetic variation among Zulu sheep sub-populations of South Africa assessed by microsatellites and mitochondrial DNA (mtDNA)

Auteur : Selepe, Mokhethi Matthews

Université de soutenance : University of Zululand

Grade : Master of Science (MS) 2018

Résumé
Human history has been completely transformed by the domestication of animals and plants over the past 10,000 years. Their domestication had a critical influence on demographic trends and was a requirement for the rise and development of civilisation. In regard to Zulu sheep, the Nguni people brought the ancestors of this breed to the east coast of South Africa (KwaZulu Natal) between 200 and 400 AD. The Zulu sheep are characterised by having either thin or fat tail (carrot shaped), multicolours, and a coat of either wool or hair. The Zulu sheep can be distinguished from other Nguni breeds by their small mouse ears, and they appear to be more woolly. In addition, the dominant colours are brown and white, black and brown, and a unique fawn colour. However, the population of Zulu sheep is reported to be declining, due to crossbreeding with exotic breeds, especially with the Dorper and Merino sheep breeds with the aim of increasing body weight. The study used two molecular markers (microsatellites and mitochondrial DNA) to investigate the genetic diversity of Zulu sheep. In experiment 1, 26 microsatellite markers were used ; (i) to confirm or disconfirm the structuration among eight Zulu sheep populations (Eshowe, Jozini, Makhathini research station, Mtubatuba, Nongoma, Nquthu, Ulundi, University of Zululand) revealed by morphological analysis, (ii) to assess the phenomenon of crossbreeding, in particular with Dorper and Merino sheep. The Damara, Dorper and South African Merino breed were included in the experiment to investigate the genetic relationship between these breeds and the Zulu sheep. The results showed that there is considerable genetic diversity among the Zulu sheep populations (expected heterozygosity ranging from 0.57 to 0.69) and the level of inbreeding was not remarkable (ranging from -0.01 to 0.16). The structure analysis results revealed that Makhathini Research Station and UNIZULU research station share common genetic structure, while three populations (Nongoma, Ulundi and Nquthu) had some admixture with the exotic Dorper breed. Thus, there is a need for sustainable breeding and conservation programmes to control the gene flow, in order to stop possible genetic dilution of the Zulu sheep. Experiment 2 assessed the genetic diversity and origin of Zulu sheep using mitochondrial DNA (D-loop). The results showed overall haplotype and nucleotide diversity iii of 0. 8113 and 0. 0115, respectively. Phylogenetic analysis showed two haplogroups (A and B). Haplogroup B lineage predominates among Zulu sheep with a frequency of 93%, while A lineage had a frequency of 7%. The analysis of mtDNA showed a high level of genetic diversity among Zulu sheep. The molecular information obtained in the present study will serve as a guideline for management and breeding strategies (reducing inbreeding and crossbreeding) for better utilisation and conservation of Zulu sheep.

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