A study of genetic variation in nellore sheep using microsatellite markers

The genetic diversity in Nellore sheep was evaluated using 15 ovine microsatellite markers proposed by Food and Agriculture Organization-International Society for Animal Genetics (FAO-ISAG). Genomic DNA was extracted from blood samples (50) using phenol-chloroform method. The number of alleles ranged from 4 (OarHH64) to 12 (MAF214) with an overall mean of 8.600±0.524. A total of 129 alleles with allele size ranging from 78 (OarCP49) to 294 bp (HSC) were identified across all loci analyzed. Allele frequency varied from 0.0104 (MAF214) to 0.5102 (OarHH64). The mean polymorphic information content was 0.819±0.210. The mean observed and expected heterozygosity values were 0.098±0.025 and 0.837±0.018, respectively. The within population inbreeding estimates (F_IS) were all positive and ranged from 0.63 (OarCP34) to 1.00 (BM827, BM6506, HUJ616 and OarHH41) with mean F_IS value of 0.919±0.025. Chi-square test revealed that all the 15 loci showed significant (P<0.01) deviation from Hardy-Weinberg equilibrium. The allele diversity (average number of alleles per locus) and gene diversity (average expected heterozygosity) reflected high level of genetic variability in Nellore sheep. Mode shift analysis revealed normal L-shaped curve indicating that Nellore population is non-bottlenecked. This study revealed that even a breed with large population size also needs genetic management for conservation and improvement.