Genetic charactersation of west african dwarf (wad) goats using microsatellite markers
Mujibi, Nagwalla Fidalis
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Goats are important respurces for small-scale farmers especially in sub-saharan Africa, since they are easy to acquire and maintain. The West African Dwarf (WAD) goat represents breeds of locally adapted Farm Animal Genetic Resources (FAnGR), which have undergone many centuries of natural selection to become adapted to their particular environment, with consequent development into very high sources of genetic diversity. This breed is said to be tolerant to sleeping sickness infection, a characteristic called trypanotolerance. However, unmanaged crossbreeding with its near geographic neighbour, the Sahelian goat is known to occur and supposedly leads to progeny with lower trypanotolerance. To access the extent of crossbreeding between the two breeds, determination of the genetic diversity, population admixture and relationships of 20 goat populations from five West African countries (Senegal, Guineas, The Gambia, Mali and Guinea Bissau) was carried out using 10 microsatellite markers. Genetic diversity was low with a mean number of allele (MNA) per locus ranging from 3.70 to 4.54, observed heterozygosity (H0) from 0.44 to 0.55 and expected heterozygosity (HE) from 0.46 to 0.54. Principal component and admixture analyses support a gradient of introgression of the Sahelian goat into the WAD goat populations, possibly following two directions: a North-South gradient from North Senegal to West Guinea and a Northeast-Southwest gradient from Mali to Guinea. Gene differentiation (FST) among populations was low (5.8%) suggesting gene flow between populations, a result confirmed by genetic distance (DA) and phylogenetic analysis. These results indicate that the level of admixture observed warrants the institution of in situ conservation, if the genetic purity and integrity of the WAD goat is to be maintained. However, a more encompassing study that includes all the West African countries known to harbour the goat breed, as well as a larger sample size with more microsatellite markers genotyped is necessary to enable a comprehensive understanding of the dynamics of introgression in the West African region.