Inheritance of coat colour in Merino sheep

Coat colour heredity patterns, from crosses and paternal backcrosses involving black and brown spotted Merino rams and full white Merino ewes, were investigated through segregation analyses. Statistical tests validate the hypothesis of a dominance with complete penetrance of: (i) full white over pigmented, (ii) black over brown, and (iii) uniform over spotted pattern, as well as, of a dominant epistasis of white/pigmented over both black/brown and uniform/spotted. Besides, the pigmented pattern segregations are independent of the sex of the individuals. These results largely agree with those already reported in literature, yet they are in contrast with the hypothesis of a full white obtainable only on a pheomelanic background coupled with a modifying effect due to the spotted gene. Moreover, epistatic effects of white have been never described.