Population studies of 17 equine STR for forensic and phylogenetic analysis.

As a consequence of the close integration of horses into human society, equine DNA analysis has become relevant for forensic purposes. However, the information content of the equine Short Tandem Repeat (STR) loci commonly used for the identification or paternity testing has so far not been fully characterized. Population studies were performed for 17 polymorphic STR loci (AHT4, AHT5, ASB2, ASB17, ASB23, CA425, HMS1, HMS2, HMS3, HMS6, HMS7, HTG4, HTG6, HTG7, HTG10, LEX3 and VHL20) including 8641 horses representing 35 populations. The power of parental exclusion, polymorphic information content, expected and observed heterozygosity and probability of identity were calculated, showing that the set of 17 STRs has sufficient discriminating power for forensic analysis in almost all breeds. We also explored the reliability of individual assignment tests in identifying the correct breeds of origin for unknown samples. The overall proportion of individuals correctly assigned to a population was 97.2%. Finally, we demonstrate the phylogenetic signal of the 17 STR. We found three clusters of related breeds: (i) the cold-blooded draught breeds Haflinger, Dutch draft and Friesian; (ii) the pony breeds Shetland and Miniature horse with the Falabella, Appaloosa and Icelandic; and (iii) The Warmblood riding breeds, together with the hot-blooded Standard-bred, Thoroughbred and Arabian.