Inheritance of yellow dun and blue dun in the Icelandic toelter horse.

The research article focuses on the influence of genetic factors on coat colors in the Icelandic toelter horse breed. This study involved analyzing different coat color outcomes from 161 progeny that resulted from mating between yellow dun and blue dun horses. The researchers concluded that a dominant dilution gene ‘D’ changes the horse color to yellow dun or blue dun based on the original color, while the palomino gene ‘c cr’ is less effective than black and blue dun, changing the color to buckskin or palomino under specific conditions.

Objective of the research

• The goal of this research was to investigate the inheritance pattern of coat colors (yellow dun and blue dun specifically) in the Icelandic toelter horse breed. The researchers observed and recorded the colors of 161 offspring from mating pairs of 10 yellow dun and 6 blue dun stallions and mares that were of 8 distinctive colors.

Influence of dominant dilution gene ‘D’

• The researchers found that a dominant dilution gene (referred to as ‘D’) directly influenced the change of bay-colored horses to yellow dun, chestnut-colored horses to also become yellow dun, and black horses into blue dun.
• No specific influence was found of the ‘D’ gene when it was present in a homozygous state (both parents contributed the same version of the gene).
• Throughout the research, 12 offspring were noticed from matings where both parents carried ‘D’. All of these offspring inherited the ‘D’ gene, and no irregular colors were recorded.

Role of the palomino gene ‘c cr’

• The palomino gene ‘c cr’ didn’t show dominance over black and blue dun. It was found to be hypostatic (less effective) to these colors.
• In its heterozygous form (‘c cr’, where one parent contributes a variant of the gene), the palomino gene resulted in the conversion of bay horses to buckskin, chestnut and sorrel-colored horses to palomino.
• Interestingly, it was found that when the ‘c cr’ gene was in a homozygous state (both parents contribute the same variant), it led to the development of blue-eyed white horses.

Conclusion

• The research concludes that the genetics behind the coat color in Icelandic toelter horses are guided by the influence of key genes such as ‘D’ and ‘c cr’. It confirmed the previous hypothesis that bay, black and chestnut hair coats can be diluted to different shades of duns using the genetic variations offered by the ‘D’ gene. On the other hand, the ‘c cr’ gene in heterozygous or homozygous form leads to palomino or blue-eyed white horses, respectively.