Spotting

The Spot mutation in pigs causes the pig to be the typical base color, with large patches of black spots (1). These spots can often be covered up with another gene like Dominant White, which is why most of the white breeds are on the spot base coat (1)(2). Breeds like Berkshire also have the spot gene, but have been selected so heavily for the black color that there is very little white (2). This is done without any additional genes. It is unknown when this color mutated, but it was likely in Asia with the Pietrain breed. It was theorized in 1982 (3) and officially mapped in 2001 (2).

The order of dominance is Black > Red > Wildtype > Spotted, meaning that any pig with the dominant black or red can "cover up" the spotting and make the entire pig look black. The spotting patterning can only be seen with two copies of the gene, so if you outcross at all, you will not get a fully spotted pig. The gene symbol is E^P

The Yorkshire, Landrace, Gloucester Old Spot, Pietrains, Berkshire, and Lindrod breeds all have the spot gene, but may not be spotted due to the dominant white that covers the spotting pattern.

Breeding with Spot:

Spot x Spot = 100% Spot

(EP/EP x EP/EP = 100% P/P)

Spot x Wildtype = 100% Spot Carriers

(EP/EP x e+/e+ = 100% EP/e+)

Spot x True Red = 100% Red,s

(EP/EP x ER/ER = 100% EP/ER)

Spot x True Black = 100% Black,s

(EP/EP x EB/EB = 100% EP/EB)

Spot x Black,s = 50% Spot, 50% Black,s

(EP/EP x EP/EB = 50% EP/EP, 50% EP/EB)

Spot x Red,s = 50% Spot, 50% Red

(EP/EP x ER/EP = 50% EP /EP, 50% ER/EP)

Spot x Spot Carrier = 50% Spot, 50% Wildtype

(EP/EP x EP/e+ = 50% EP/EP, 50% EP/e+)

Red,s x Red,s = 25% True Red, 50% Red,s, 25% Spot

(ER/EP x ER/EP = 25% ER/ER, 50% ER/EP, 25% EP/EP)

Black,s x Black,s = 25% True Black, 50% Black,s, 25% Spot

(EB/EP x EB/EP = 25% EB/EB, 50% EB/EP, 25% EP/EP)