Association between candidate gene markers and harness racing traits in Italian trotter horses

Knowledge of genes involved in the variability of performance of racehorses is, in general, limited. In this study, six single nucleotide polymorphisms (SNPs) of five genes were genotyped in 412 Italian Trotter horses (ITHs) and possible associations between five segregating SNPs and harness racing performance (best racing time in career, earnings, placings, starts, and wins) were investigated. These markers were in genes related to exercise physiology (creatine kinase muscle, CKM; and cytochrome c oxidase, subunit 4, isoform 2, COX412), gait patterns (DMRT3), carbohydrates metabolism (GCK) and morphological phenotypes (LCORL). Two SNPs of the GCK gene were used to predict haplotypes. The mutate A allele of the DMRT3 was almost fixed in the ITHs. Single marker association analyses showed that the COX412 SNP was significantly associated with variation of number of starts (P = 0.0003), and wins (P = 0.0045). This COX4I2 polymorphic site seems therefore to be a promising marker for racing longevity and durability. A haplotype of the GCK was instead positively associated with best racing time (P = 0.0118), earnings (P = 0.0370) and wins (P = 0.0061). This is the first study highlighting the effect of GCK on harness racing performance in horses. Confirmation of these results in independent populations would be important to evaluate the inclusion of the SNPs in marker-assisted selection programmes in ITHs.