Study of genetic variability among Gohilwadi, Surti and Zalawadi goats using microsatellite analysis
Fatima, Shadma (2006) Study of genetic variability among Gohilwadi, Surti and Zalawadi goats using microsatellite analysis. Masters thesis, College of Veterinary Science and Animal Husbandry, Anand Agricultural University, Anand, Gujarat, INDIA.
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The present study was undertaken for population genetic analysis of microsatellite variation in three indigenous goat breeds viz: Gohilwadi, Surti and Zalawadi using 19 microsatellite markers selected from the list suggested by International Society for Animal Genetics (ISAG). Out of 19 microsatellites, 18 microsatellites were amplified and observed number of alleles ranged from four (in Oar JMP-29) to fifteen (in ILSTS-030 and -034) with total 178 alleles across three breeds. The overall heterozygosity, PIC and Shannon index values were 0.61, 0.60 and 1.50 indicating high gene diversity. The highest observed heterozygosity were found in Gohilwadi and minimum in Surti goat breed. Genetic distance was least (0.128) between Gohilwadi and Zalawadi and highest between Gohilwadi and Surti (0.1951). In all populations low inbreeding was indicated (mean FIS = 0.0192, FIT = 0.0914) within and among the breeds. Genetic differentiation between breeds was moderate with a mean FST value of 0.073 which showed that the average proportion of genetic variation explained by breed differences was 7.3%. Non-significant heterozygote excess on the basis of IAM, TPM and SMM models, as revealed from Sign, Standardized differences and Wilcoxon sign rank tests, along with a normal ‘L’ shaped distribution of mode–shift test, indicated no bottlenecks in the recent past in Zalawadi and Gohilwadi breeds whereas Surti breed exhibited bottleneck only with IAM under all the three tests. The clusters obtained on phylogenetic tree generated from Nei’s genetic distance matrix agreed with the geographic origin of the breed. Deviations from Hardy-Weinberg equilibrium were noted for most of the locus. Also, significant linkage disequilibrium was detected between two pairs of syntenic microsatellite loci. The time of divergence in Zalawadi and Gohilwadi goats, Zalawadi and Surti, and Gohilwadi and Surti was estimated to be 640, 760 generations, and 970 generations. The population genetic structure and geneflow among goat breeds using 18 polymorphic microsatellite loci using program Geneclass. Fourteen microsatellite loci selected for population assignment inferred using most likelihoods ratios. Bayesian and frequency-based assignment tests revealed significant population structure and provide support for three subpopulations. All the three populations showed some degree of admixture. The 14 loci selected when used together correctly assigned 96.2% of individuals to their original populations. These 14 markers can be used for genetic investigations and assessing population structure in Indian goat populations. The study analyzed the population structure of these populations and contributed to the knowledge and genetic characterization of three Indian indigenous goat populations. In addition, the microsatellites recommended by ISAG proved to be useful for the biodiversity studies in Indian goat breeds.
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