From the moment I announced that I was searching for a grulla (pronounced “grew-ya”) filly, I was met with quizzical looks. It would seem that most folks (if they’re familiar with Morgans at all) think that the traditional colors of black, bay and chestnut are the only colorful wrappers that Morgans come with. NOT TRUE! J Morgans can come in an amazing variety of colors, all thanks to dilution genes.

 

Dilution genes take a horse’s base coat color and dilute it to some degree. To really simplify what can be a complex subject, let’s look at a few examples:

 

¨ Bay horse, diluted by one cream gene: BUCKSKIN

¨ Chestnut horse, diluted by one cream gene: PALOMINO

¨ Black horse, diluted by one cream gene: SMOKEY BLACK

 

Then we can shake things up some more, and throw in a second cream gene. This means that the horse would have to inherit one cream gene from either of its parents. This second gene intensifies the level of dilution to the base coat.

 

¨ Bay horse, diluted by two cream genes: PERLINO

¨ Chestnut horse, diluted by two cream genes: CREMELLO

¨ Black horse, diluted by two cream genes: SMOKEY CREAM

 

Sounds fantastic, right? And it is. But for me, it gets even better when you add the dun gene into the mix! Dun is a separate dilution gene that lightens both red and black hair on a horse. Because it is a dominant gene, every dun horse MUST have at least one dun parent. Unlike the cream gene, there is no appreciative phenotypic difference in a horse with only one dun gene (heterozygous) or two dun genes (homozygous). Let’s see what we get now:

 

¨ Bay horse, diluted by the dun gene: BAY DUN

¨ Bay horse, diluted by the dun gene & one cream gene: DUNSKIN

¨ Bay horse, diluted by dun gene & two cream genes: PERLINO DUN

 

¨ Chestnut horse, diluted by the dun gene: RED DUN

¨ Chestnut horse, diluted by the dun gene & one cream gene:  DUNALINO

¨ Chestnut horse, diluted by the dun gene & two cream genes: CREMELLO DUN

 

¨ Black horse, diluted by the dun gene: GRULLA

¨ Black horse, diluted by the dun gene & one cream gene: SMOKEY GRULLA

¨ Black horse, diluted by the dun gene & two cream genes: SMOKEY CREAM GRULLA

 

PLEASE NOTE: This is a ridiculously simplified look at color genetics in action! We haven’t even begun to dig into all of the other known dilution genes here, such as Silver Dapple, Champagne, or any of the pinto patterns. There’s also lots of opportunity for discussion in the “bay vs. brown” agouti area…  J

 

For more clarity and educationally sound explanations, please visit Morgan Colors, Dun Central Station and the Rainbow Morgan Horse Association websites. You will find full color examples of every Morgan under the colorful sun...

Dun dorsal on a grulla (tested D/d by UC Davis)

“Zippers” going up the legs.

Grulla filly on the left, brown buckskin filly on the right.