DETERMINATION OF EVOLUTIONARY RELATIONSHIPS AMONG SHEEP BREEDS USING MICROSATELLITES

Eight ovine microsatellite loci were amplified in 40 to 50 unrelated i ndividuals from six sheep populations representing five breeds: Romney , Border Leicester, Suffolk, Awassi, and both Australian and New Zeala nd Merino. For all of the microsatellite loci analyzed, there were hig hly significant differences in allele frequencies between samples from the different breeds. The allele frequencies generated can be used to determine the breed of an individual, given that it comes from one of the above breeds, to a high degree of accuracy. There were also some alleles that were found in only one breed, although these alleles were at such low frequencies that they are unlikely to be useful as marker s for a breed. Genetic distances between breeds were obtained using Ne i's formula to construct a phylogenetic tree. The tree grouped the Mer ino's in one branch and the Border Leicester, Suffolk, and Romney in a nother branch, while the Awassi, which was used as an outgroup, had it s own branch. Using Nei's unbiased genetic distance formula to calcula te the time of divergence of the British breeds from the Merino and th e time of divergence between the Australian and the New Zealand Merino , we obtained t = 1094 and t = 227 years, respectively. Microsatellite genotyping in sheep appears to provide a useful tool for examining th e evolutionary relationships between breeds. (C) 1994 Academic Press, Inc.