Genome-wide evaluation of effective population size in some Iranian sheep breeds using linkage disequilibrium information

The aim of the present study was to estimate the effective population size (Ne) in some Iranian sheep breeds using genome wide SNP data. A total of 217 animal samples consisting of 45, 37, 34, 35, 45 and 11 samples from Zel, Afshari, Moghani, Qezel, Lori-Bakhtiari and a wild-type of Iranian sheep breeds, genotyped by Illumina OvineSNP50K Beadchip assay were used in this study respectively. This study has been performed in collaboration with the Ovine HapMap project. The Ne was estimated using linkage disequilibrium across 4 up to 3500 generations ago. The result of principal component analysis (PCA) indicated that all breeds will be separated from each other in the first two principal components. Average expected and observed heterozygosity for different breeds ranged 0.36-0.37 and 0.37-0.43 respectively. The Ne results showed a decreasing trend over the last 3500 generations for all breeds, with an increasingly slope since about last 550 generations. The Ne in Iranian sheep breeds for 4 generations ago were ranged from 9 up to 89. The highest historically effective population size was found for Zel breed (89 heads) and the lowest for Afshari (44 heads) and wild_type (9 heads) sheep breeds. Generally, the results indicated that although a considerable genetic variation exists in these populations, however Ne has been decreased strongly in Iranian sheep breeds especially in Afshari and wild-type sheep breeds during recent years and designing of appropriate programs is necessary to conserve remaining purebred animals of these indigenous sheep breeds.