Molecular evidences of mutation-drift equilibrium in Punganur breed of cattle

To evaluate Punganur cattle 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). The observed gene diversity (He) and expected equilibrium gene diversity (Heq) were estimated under different models of microsatellite evolution. All the 20 loci were found to exhibit gene diversity excess under IAM and TPM, while 19 loci were having gene diversity excess under SMM. All the three statistical tests, viz., sign test, standardized differences test, and Wilcoxon sign rank test, revealed significant (P<0.01) deviation of Punganur cattle population from mutation-drift equilibrium under all the three models of mutation. Furthermore, the qualitative test of allele frequency distribution in Punganur cattle population revealed a strong mode shift from the normal L shaped form suggesting that the population had experienced genetic bottleneck in the recent past. The occurrence of genetic bottleneck might have led to the loss of several rare alleles in the population, which point towards the need for efforts to conserve this important cattle germplasm.