Mushroom (Mu)
The mushroom gene is currently only found in the Shetland Pony. The gene must be homozygous (MuMu) on a red-based coat, chestnuts or bays, to show the dilution. Any horses that show mushroom dilution will show as a mushroom base.
![mushroom](https://horsefable.wiki/wp-content/uploads/2021/11/mushroom-3.png)
The mushroom gene is currently only found in the Shetland Pony. The gene must be homozygous (MuMu) on a red-based coat, chestnuts or bays, to show the dilution. Any horses that show mushroom dilution will show as a mushroom base.