Detection of occurrence of a recent genetic bottleneck event in Indian hill cattle breed Bargur using microsatellite markers

• Published in: Tropical animal health and production 2012-12, Vol.44 (8), p.2007-2013
• Main Authors: Ganapathi, Palanisamy, Rajendran, Ramanujam, Kathiravan, Periasamy
• Format: Article
• Language: English
• Subjects: Animal populations; Animals; Biomedical and Life Sciences; Cattle; Cattle - genetics; Demography; Drift; Evolution; Evolutionary genetics; Frequency distribution; Gene frequency; Genetic Drift; Genetic markers; Genotype; Germplasm; Heterozygosity; India; Life Sciences; Male; Microsatellite Repeats; Microsatellites; Models, Biological; Multilocus Sequence Typing - veterinary; Mutation; Original Research; Polymerase Chain Reaction - veterinary; Population genetics; Statistical analysis; Veterinary Medicine/Veterinary Science; Zoology
• ISSN: 0049-4747; 1573-7438
• DOI: 10.1007/s11250-012-0171-8

The effective number of breedable individuals is a crucial determinant for maintaining genetic variability within a population. The population of Bargur, the hill cattle of South India, has gone down drastically by more than 93 % in the past three decades, and only a few thousand animals are available at present. The present study was undertaken to evaluate Bargur cattle for mutation drift equilibrium and to detect the occurrence of recent genetic bottleneck event, if any, in this population. About 50 unrelated animals, true to the type, were sampled and genotyped at 25 microsatellite loci. The mean observed heterozygosity (0.808 ± 0.023) was higher than the mean expected heterozygosity (0.762 ± 0.008) with 15 out of 25 microsatellite loci exhibiting heterozygosity excess when assumed under Hardy–Weinberg equilibrium. To evaluate Bargur 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 ( H e ) and expected equilibrium gene diversity ( H eq ) were estimated under different models of microsatellite evolution. All the 25 loci were found to exhibit gene diversity excess under IAM and TPM, while 22 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