Genetic diversity in the modern horse illustrated from genome-wide SNP data.
Authors: Petersen Jessica L, Mickelson James R, Cothran E Gus, Andersson Lisa S, Axelsson Jeanette, Bailey Ernie, Bannasch Danika, Binns Matthew M, Borges Alexandre S, Brama Pieter, da Câmara Machado Artur, Distl Ottmar, Felicetti Michela, Fox-Clipsham Laura, Graves Kathryn T, Guérin Gérard, Haase Bianca, Hasegawa Telhisa, Hemmann Karin, Hill Emmeline W, Leeb Tosso, Lindgren Gabriella, Lohi Hannes, Lopes Maria Susana, McGivney Beatrice A, Mikko Sofia, Orr Nicholas, Penedo M Cecilia T, Piercy Richard J, Raekallio Marja, Rieder Stefan, Røed Knut H, Silvestrelli Maurizio, Swinburne June, Tozaki Teruaki, Vaudin Mark, M Wade Claire, McCue Molly E
Journal: PloS one
Summary
# Editorial Summary: Genetic Diversity in Modern Horse Breeds Using genome-wide SNP analysis across 814 horses from 36 breeds, researchers have provided the first comprehensive map of genetic relationships in the modern horse, revealing that breed clustering largely reflects geographic origins and documented breeding histories rather than phenotypic classification alone. The study employed FST calculations and distance-based analysis to quantify both between-breed divergence and within-breed genetic diversity, identifying clear patterns: young breeds and those with ongoing outcrossing or large founding populations showed minimal genetic differentiation, whilst intensively selected or long-closed populations displayed markedly reduced diversity, indicating previous bottlenecks or stringent selective pressure. Key findings include the identification of which breeds maintain substantial genetic variation—important for long-term population health—and which have become genetically isolated, with implications for managing inbreeding coefficients and maintaining trait plasticity. For practitioners, these data underscore why genetic testing and informed breeding decisions matter differently across breeds: a population at breed establishment (with high diversity) faces different genetic management considerations than an ancient closed breed (with restricted diversity), and outcrossing decisions can be evaluated against genome-wide evidence rather than pedigree alone. The research framework also establishes a foundation for future genome-wide association studies, enabling more precise identification of genomic regions under selection for performance, conformation, and disease traits—directly applicable to breeding programmes and predictive health management.
Read the full abstract on PubMed
Practical Takeaways
- •Understanding breed genetic diversity helps breeders make informed decisions about outcrossing and selective breeding strategies to maintain genetic health
- •Closed breeds with long histories show reduced diversity, indicating potential risk for genetic disorders—genetic testing and careful pedigree management are important for these populations
- •This genomic data provides a baseline for future studies linking specific genetic variants to performance traits and disease susceptibility in horses
Key Findings
- •Genome-wide SNP analysis of 814 horses from 36 breeds reveals breed relationships that largely reflect geographic origins and known breed histories
- •Low population divergence observed between early-stage breeds and those with high within-breed diversity due to large population size or ongoing outcrossing
- •Populations with low within-breed diversity include those experiencing population bottlenecks, intense selective pressure, or closed populations with long breed histories