Description:
Dilute is one of the lesser-studied genes in chickens. It causes the overall red coloration from gold or mahogany to be a lighter shade of orange. It is one of the genes used to make the Buff variety. It only affects the pheomelanin (red pigment) production in a bird (1) (2).
Buff, at least with Orpingtons, Minorca, and likely Pratt (3) are a combination of Dilute, Columbian restriction, Mahogany, Champagne Blonde, and possibly other genes (4). However, with Rocks and possibly other breeds, the same color can be achieved with Dominant White instead of dilute (1). More research needs to be done overall on the buff variety and Dilute genes.
From general descriptions of buff crossings with several different breeds (4), it appears that Dilute is incomplete dominant, with only one copy of the gene causing the pigment to be slightly more red. However, it isn't known how much of that "washed out" red look is due to Dilute and how much is due to the combination of other genes.
The chromosome, allele, and other scientific listing are based on a reported "dilute" gene. It is unknown if this is the same dilute gene that affects plumage pigment, or reference to another unknown gene (5).
The APA recognizes Buff as a variety in the following breeds:
Ameraucana, Brahma, Catalana, Cochin, Cornish, Naked Neck, Orpington, Wyandotte, and Plymouth Rock, (6) though Plymouth Rocks and Brahmas for sure do not utilize the dilute gene to create buff.
Breeding with Dilute:
Note: Red here is any combination of genes that creates the red look, including the natural gold and mahogany. Dilute is assumed to be acting on buff here.
Dilute x Dilute = 100% Dilute
Dilute x Red = 100% Washed - Out Red
Dilute x Washed-Out Red = 50% Dilute, 50% Washed Out Red
Washed - Out Red x Washed-Out Red = 25% Dilute, 50% Washed-Out Red, 25% Red
Washed-Out Red x Red = 50% Washed-Out Red, 50% Red
References & Further Reading
Carefoot, W. C. "Evidence that the eumelanin restrictor genes (Co) and (Db) are present in the genome of the Buff Rock bantam." British Poultry Science 36.2 (1995): 205-207.
Somes Jr, Ralph G., and J. Robert Smyth Jr. "Feather Phaeomelanin Intensity in Buff Orpington, New Hampshire and Rhode Island Red Breeds of Fowl: 3. Relative Quantities of Fractionated Phaeomelanin Pigments." Poultry Science 44.1 (1965): 276-282.
Campo, J. L., and F. Orozco. "A genetic study of the buff columbian color pattern in prat chickens." Journal of Heredity 75.1 (1984): 19-22.
Brumbaugh, J. A., and W. F. Hollander. "Genetics of buff and related color patterns in the fowl." Poultry Science 45.3 (1966): 451-457.
Sanders, Gabriele, et al. "cDNA encoding the chicken ortholog of the mouse dilute gene product Sequence comparison reveals a myosin I subfamily with conserved C-terminal domains." FEBS letters 311.3 (1992): 295-298.
American Poultry Association. (2023). American Standard of Perfection (45th ed.)
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