Genetic Diversity of Awassi Sheep Reared in Fertile Crescent Based on Microsatellites: A Review

Abstract

In general, many domestic breeds of livestock evolved to different geographical regions, Awassi sheep in particular, adapted to Fertile Crescent region where cradle of domestication took place. Awassi sheep has tremendous genetic diversity compared to other domestic sheep breeds of the world. Nowadays, Awassi sheep is in danger of losing their unique and ancient genetic diversity as a result mainly of unwarranted crossing with high-yielding exotic breeds. Another reason for losing diversity is reduction in the population size of Awassi sheep in their origin region of the Fertile Crescent. Unveiling genetic diversity marks the inaugural phase in the execution of breeding and conservation initiatives. Previous literature revealed that microsatellite markers were widely used and accepted until nowadays as useful molecular markers for evaluating genetic diversity of sheep populations along with other markers such as Single Nucleotide Polymorphisms (SNP). Most studies based on microsatellite markers provided information on genetic diversity parameters (e.g. observed and expected heterozygosity, PIC, alleles number, inbreeding coefficient, effective population size, genetic distances values and cluster analyses) within and among Awassi populations. These markers enabled phylogenetic relationships among populations by tree building approach based on genetic distance values. On the other hand, crossbreeding practices are thought to contribute to the genetic erosion of the original Awassi sheep breed, while a reduction in population size is anticipated to have adverse effects on genetic diversity. In this work, we reviewed the microsatellite-based studies which have been published for detecting genetic diversity of Awassi sheep breed in various countries of Fertile Crescent.