The genetic structure of Spanish Celtic horse breeds inferred from microsatellite data

Partition of the genetic variability, genetic structure and relationships a mong seven Spanish Celtic horse breeds were studied using PCR amplification of 13 microsatellites on 481 random individuals. In addition, 60 thoroughb red horses were included. The average observed heterozygosity and the mean number of alleles were higher for the Atlantic horse breeds than for the Ba learic Islands breeds. Only eight percentage of the total genetic variabili ty could be attributed to differences among breeds (mean F-ST approximate t o 0.08; P < 0.01). Atlantic breeds clearly form a separate cluster from the Balearic Islands breeds and among the former only two form a clear cluster ing, while the rest of Atlantic breeds (Jaca Navarra, Caballo Gallego and P ottoka) are not consistently differentiated. Multivariate analysis showed t hat Asturcon populations, Losina and Balearic Islands breeds are clearly se parated from each other and from the rest of the breeds. In addition to thi s, the use of the microsatellites proved to be useful for breed assignment.