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Deemed University (2004)

Genetic characterization of indigenous goat populations of Ethiopia using Microsatellite DNA markers

ALEMU TUCHO TESFAYE

Titre : Genetic characterization of indigenous goat populations of Ethiopia using Microsatellite DNA markers

Auteur : ALEMU TUCHO TESFAYE

Université de soutenance : Haryana, India : National Dairy Research Institute, Deemed University

Grade : Doctor of Philosophy PhD 2004

Résumé
Indigenous goats are an important resource for African farmers, providing meat, milk, manure, fibres and hides, and satisfying various cultural and religious functions. In Africa, the survival of many indigenous goat populations is threatened by diseases, adverse climatic conditions, civil strife, pressure of economic development, abandonment of traditional farming practices, and more importantly through crossbreeding or replacement with animals from the developed world. Indigenous Ethiopian goat genetic resources have been classified phenotypically into 11 types. These are Abergalle, Arsi-Bale, Afar, Central Highland, Gumez, Hararghe Highland, Keffa, Long-eared Somali, North-West Highland, Short-eared Somali, and Woyto-Guji. In the present investigations two main studies were carried out. The first study dealt with the genetic diversity within and between the Ethiopian goats. The second study dealt with the genetic diversity and relationship of the Ethiopian goat in relation to goat populations from other countries of African and outside African continents. For the first study, the 11 indigenous Ethiopian populations were sampled. In the second study, five populations from other African countries [(Boran-Galla and Small East African from Kenya), WAD from Guinea Bissau (West Africa), Tswana from Botswana and Baladie from Egypt] and four populations from outside African continent (Italian Alpine from Italy, Ardi from Saudi Arabia, Hair from Turkey and Zalaajinistiin from Mongolia) were sampled. All the populations were assessed for genetic diversity using 15 microsatellite loci. A wide range of statistical analyses were performed on the data to answer questions on population genetics diversity, relationship and differentiation. The genetic diversities observed in both the Ethiopian and non-Ethiopian populations were similar. The analysis of molecular variance (AMOVA) indicated a greater proportion of the genetic diversity within the Ethiopian populations than between populations. Genetic distances were observed to be relatively small for Ethiopian populations. The high correlations observed between geographical distances and genetic distances for Ethiopian populations supported this result. On the other hand, relatively large genetic distances were observed between Ethiopian and Non-Ethiopian populations with exception of Kenyan populations. The results have shown that more than 60% of the goat populations showed significant inbreeding effect, which leads to loss of genetic diversity. Phylogenetic trees, population structure and principal component analyses showed that all the Ethiopian populations are genetically distinct from all the reference populations except with two Kenyan populations. However, they also indicated that all the Ethiopian goats populations are very closely related to each other. Our results indicate that the 11 Ethiopian populations can be grouped as eight distinct genetic entities : Arsi-Bale, Gumez, Keffa, Woyto-Guji, Abergalle, Afar, Highland goats (previously separated as Central and North West Highland) and the goats from the previously known Hararghe, Southeastern Bale and Southern Sidamo provinces (Hararghe Highland, Short-eared Somali and Long-eared Somali goats). Weitzman analysis indicates that about 75% of the total genetic diversity of the Ethiopian goats is present in four breeds : Afar, Abergalle, Gumez and Keffa with marginal loss of diversity of 24.32%, 19.22%, 16.59% and 12.99%, respectively. Genetic differentiation tests showed that all the Ethiopian and non-Ethiopian populations were well differentiated. Individuals from Ethiopian populations were assigned to their source populations with a low degree of accuracy indicating their genetic similarity. However, the proportion of correct assignment for the non-African population was higher than that for the Ethiopian populations. Results support the theory of two separate entry points for the goats into the African continent : the Isthmus of Suez for the North African and the horn of Africa for the Eastern African goats. Ethiopia hosts a large indigenous goat genetic resource adapted to the complexity agricultural production systems of the country ; it represents a unique resource that has potential for further and future genetic improvement of its productivity.

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