Genetic structure and variability within and among populations of the fat-tailed Barbarine sheep breed using microsatellites markers

This study investigates the genetic diversity and the structure of the most dominant native fat-tailed Tunisian sheep breed (Barbarine, BAR) using microsatellite markers. Blood samples from 183 BAR animals, belonging to 4 subpopulations according to phenotypic traits, were collected across all regions in Tunisia. BAR animals and 31 Appenninica Italian sheep breed (APP) used as an out-group were genotyped at 17 microsatellites loci. A total of 270 alleles were identified with average gene diversity equal to 0.812. The mean observed heterozygosity (0.745) and allelic richness (8.09) estimates were high within BAR breed highlighting notable levels of genetic diversity. The low FIS (0.078) and FIT (0.084) values indicate low level of inbreeding within this breed while a low FST estimate (0.007) shows that the subpopulations are not genetically differentiated. The clustering analysis performed with ‘structure’ detected the absence of substructures and the clear uniqueness of the BAR. Tomiuk and Loeschcke’s DTL genetic distance values confirmed the distinction between APP and BAR breeds. Results arising from our microsatellites analysis represent a starting point for the valorization of this indigenous Tunisian sheep breed. A suggestion was made to monitor its genetic variability and for the preservation of this breed for the next generations.Keywords: Tunisian Barbarine sheep breed, microsatellite markers, genetic variability, population structureAfrican Journal of Biotechnology, Vol. 13(1), pp. 44-54, 1 January, 201

Genetic diversity, structure, and breed relationships in Tunisian sheep

The aim of this research was (i) to quantify the levels of genetic variability in Tunisian sheep breeds and (ii) to investigate their population structure and the extent of admixture, to provide information for their conservation. Blood samples from 249 sheep, belonging to 5 breeds and 1 crossbred population were collected across different agroecological zones in Tunisia. Tunisian sheep and 31 Appenninica Italian sheep (APP), used as an out-group, were genotyped at 17 microsatellite loci. All the sheep breeds investigated were genetically diverse, as evidenced by the high allele (>7) and gene (>0.7) diversity values. The average F-IS (0.105) and F-IT (0.132) values indicated significant levels of inbreeding within these breeds. The average F-ST estimate (0.030) between all breeds and Reynolds' genetic distance revealed the close relationship among native Tunisian breeds and their clear distinction from the D'man exotic breed and APP. The clustering analysis performed with STRUCTURE also evidenced that native Tunisian breeds could be considered as subpopulations belonging to one breed. The high level of admixture found also reflects the sheep breeding history of Tunisia. Application of this knowledge may be useful in breeding programs and genetic management of breeds. These findings represent a starting point for the characterization of Tunisian sheep breeds suggesting the need to set up accurate conservation measures aiming to safeguard and monitor their genetic variability

Contribution of microsatellites markers in the clarification of the origin, genetic risk factors, and implications for conservation of Tunisian native sheep breeds

The genetic diversity and genetic relationship of the two main groups of African sheep, thin-tailed and fat-tailed sheep, represented by the indigenous Tunisian sheep breeds \u201cBarbarine\u201d (BAR, fat-tailed) and \u201cQueue Fine de l\u2019Ouest\u201d (QFO, thin-tailed) were investigated. The genotypes of 110 animals belonging to these two breeds and their crossbreed (CRO) were assessed using 17 microsatellite markers. The results showed high levels of genetic diversity and a total of 256 alleles were identified in the whole population. The mean values of observed and expected heterozygosity were 0.719 and 0.789, respectively, and the mean allelic richness estimate was 10.89. The average FIS (0.112) and FIT (0.118) values over all loci indicated a notable level of inbreeding within the whole population. However, the FST value (0.007) showed a low level of genetic differentiation between these two native breeds. The high level of both gene flow and molecular coancestry coefficient detected between the two breeds and their CRO revealed an old miscegenation between the BAR and QFO breeds. The clustering analysis performed with the STRUCTURE software confirmed gene flow between these two breeds. Results arising from this study provide evidence regarding the genetic structure and variability of the two main local sheep breeds, and the implications of their actual management, which indicates the need for an urgent conservation strategy in order to prevent significant gene flow and preserve the remaining breed specificity for future generations