Exploring the polygenic landscape of wool traits in Turkish merinos through multi-locus GWAS approaches: Karacabey Merino.

This study investigated the genetic basis of wool traits in Karacabey Merino sheep, a dual-purpose breed developed in Northwest Türkiye. Heritability estimates were moderate for fibre diameter (FD; h² = 0.360) and greasy fleece weight (GFW; h² = 0.443), but low for staple length (SL; h² = 0.119), suggesting that while some traits may respond well to selection, others may require larger datasets or complementary approaches to capture their underlying genetic variation. Genetic and phenotypic correlations with growth traits revealed complex interactions, indicating that selection for wool traits may have trade-offs with growth performance, a key consideration in the breeding of dual-purpose sheep. To identify genomic regions associated with these traits, we employed multiple multi-locus GWAS methods (mrMLM, FASTmrMLM, FASTmrEMMA, pLARmEB, and ISIS EM-BLASSO). To enhance the robustness of the findings and reduce the likelihood of false positives, a stringent significance threshold (LOD ≥ 5) was applied. Post hoc power analysis further demonstrated that a considerable proportion of the identified QTNs exceeded the critical statistical power threshold (≥ 0.8), providing greater confidence in their biological relevance. Importantly, several loci were consistently detected across different models, underscoring their stability and potential value as reliable markers. Together, these findings provide novel insights into the polygenic architecture of wool traits in Karacabey Merino sheep and identify promising targets for marker-assisted selection. Beyond their immediate relevance to this breed, the results also contribute to a broader understanding of the genetic regulation of wool traits in dual-purpose sheep. Future studies incorporating functional validation, gene expression analyses, and replication in independent populations will be essential to confirm the functional significance of the identified loci. Such efforts would not only improve the reliability of these associations but also enable their practical application in breeding programmes aimed at optimising both wool quality and growth performance.