Genetic architecture and bottleneck analyses of Salem Black goat breed based on microsatellite markers

Abstract

Aim: The present study was undertaken in Salem Black goat population for genetic analysis at molecular level to exploit the breed for planning sustainable improvement, conservation and utilization, which subsequently can improve the livelihood of its stakeholders. Materials and Methods: Genomic DNA was isolated from blood samples of 50 unrelated Salem Black goats with typical phenotypic features in several villages in the breeding tract and the genetic characterization and bottleneck analysis in Salem Black goat was done using 25 microsatellite markers as recommended by the Food and Agricultural Organization, Rome, Italy. The basic measures of genetic variation were computed using bioinformatic software. To evaluate the Salem Black goats for mutation drift equilibrium, three tests were performed under three different mutation models, viz., infinite allele model (IAM), stepwise mutation model (SMM) and two-phase model (TPM) and the observed gene diversity (He) and expected equilibrium gene diversity (Heq) were estimated under different models of microsatellite evolution. Results: The study revealed that the observed number of alleles ranged from 4 (ETH10, ILSTS008) to 17 (BM64444) with a total of 213 alleles and mean of 10.14±0.83 alleles across loci. The overall observed heterozygosity, expected heterozygosity, inbreeding estimate and polymorphism information content values were 0.631±0.041, 0.820±0.024, 0.233±0.044 and 0.786±0.023 respectively indicating high genetic diversity. The average observed gene diversities (He) pooled over different markers was 0.829±0.024 and the average expected gene diversities under IAM, TPM and SMM models were 0.769±0.026, 0.808±0.024 and 0.837±0.020 respectively. The number of loci found to exhibit gene diversity excess under IAM, TPM and SMM models were 18, 17 and 12 respectively. Conclusion: All the three statistical tests, viz., sign test, standardized differences test and Wilcoxon sign rank test, revealed significant deviation of Salem Black goats from mutation-drift equilibrium under IAM and TPM models, however, nonsignificant deviation under SMM model. The qualitative test of mode shift analysis supported the results under SMM indicating the absence of the genetic bottleneck in the recent past in Salem Black goats.