Molecular characterization of parasite resistant/susceptible Uruguayan Merino lambs

Abstract

Gastrointestinal parasites (GIP) are one of the main sanitary and economic limitations for Uruguayan sheep production. Many authors suggest a possible relationship between microsatellites and sheep parasite resistance. Based on extreme fecal worm egg count-expected progeny difference (FECEPD), 50 resistant (R) and 50 susceptible (S) lambs were chosen from a Merino flock. In order to investigate the genetic variability and structure in this flock, four polymorphic microsatellites (McM214, McM130, McM357 and CSRD2138) which are potentially associated with quantitative trait loci (QTL) for parasite resistance were analyzed. The number of alleles varied from 8 to 13 showing different frequencies; polymorphic information content values were >0.5 and the observed heterozygosity ranged from 0.735 to 0.773. A considerable genic and genotypic differentiation between R and S subpopulations was observed. McM214 showed a significant deviation from Hardy-Weinberg equilibrium in whole herd and S population. Fixation Indices (FIS) values also indicated a heterozygote excess in the entire population. McM214 showed linkage disequilibrium with McM357 in the R sample, and with McM130 in the S sample. Population structure analysis proved the origin of two clusters (subpopulations) from two different lines (K = 2, similarity coefficient = 0.979). Polymorphism of these markers could be used in association analysis with GIP resistance / susceptibility.