Genetic Background of the Polish Primitive Horse (Konik) Coat Color Variation-New Insight into Dun Dilution Phenotypic Effect.

This research article investigates the genetic basis for coat color variation in the Polish primitive horse (PPH, Konik) breed. Although only blue dun coat color is officially permitted for this breed, the researchers found a high prevalence of genetically bay dun-colored horses, as well as evidence of other genetic variants affecting coat color.

Introduction and Background

• The Polish primitive horse, also known as the Konik, is a breed of horse that, officially, only has the blue dun color, caused by the action of the dun allele on a black base coat.
• Despite this official rule, there is significant variation in coat color within the breed.
• The researchers wanted to understand the genetic basis for this variation. Specifically, they looked at known genes related to coat color (ASIP, MC1R, TBX3, SLC36A1, SLC45A2, PMEL17, and RALY) and screened for new genetic variants in the ASIP gene and a region of the TBX3 gene associated with dun dilution.

Results and Findings

• The researchers found that there was a significant relationship between the TBX3 gene and the degree of dun coat dilution, suggesting that the gene’s effect on dun color may be more complex than previously understood, with an additional allele potentially contributing to color variability.
• A large number (35%) of the PPH horses recorded as having a blue dun coat actually had a genetically bay dun color. This discrepancy is likely due to difficulty in distinguishing the two types visually, and might also be influenced by an independent locus upstream of the ASIP gene, which is known to darken the typical bay pigmentation shade.
• No evidence was found for some other coat color dilution variants (champagne, silver, or cream) in the PPH breed.

Conclusion

• This research provides new insight into the genetics of coat color in the Polish primitive horse breed, identifying additional genetic factors that could account for the observed variation in coat color.
• It also highlights the discrepancy between the official breed standard and the actual genetic coloration observed, raising questions about breed classification and the accuracy of visual phenotype recording.