Caractérisation de la race bovine Somba à l’aide de marqueurs moléculaires

The polymorphism of four categories of genome markers— 11 blood group systems, 5 lactoprotein loci, 2 blood protein loci and 33 microsatellites, i.e. 51 loci in total—was analyzed in four cattle populations or “breeds” from West Africa: the Somba and Lagoon taurine breeds, the Sudanese zebu Peul population and the Borgu population, crossbred between taurine and zebu. The aim of the study was to characterize the polymorphism of the Somba breed and to evaluate its genetic distance with the other three populations, especially the Lagoon breed, with which it shares a high phenotypical resemblance. Whatever the category of markers or the method used, the four populations were clearly separated. Based on the blood group systems, the most marked differences were observed between taurine and zebu breeds especially for the A, B and S systems. The typical high allele frequencies of Alb S and Hb B were observed in zebus, as well as the well-known predominance of the α s1 -Cn C , β-Cn A2 , κ- Cn A haplotype, in contrast with the α s1 -Cn B , β-Cn A1 , κ-Cn B haplotype of African taurines. Based on microsatellites, reciprocal averaging highlighted the discriminating effect of ETH 225 139 allele, whose frequency was very high in the Somba breed, and Hel 13 182 and INRA 037 114 , which were apparently specific to zebu and Lagoon breeds, respectively. These allele frequencies in the Borgu population were roughly intermediate between those in zebus and taurine breeds. The study also tried to determine whether it was possible to identify the population of origin based on the knowledge of the 33-microsatellite genotype of an animal. Results showed that 97% of the animals were correctly classified; errors concerned zebus incorrectly classified as Borgus and vice versa.