The origin of the spotted
gene in the Tennessee Walking Horse breed is something of a mystery.
As you can see from the thumbnails below, spots were limited to
sabino and overo markings in roans until the appearance of Nell
Overstreet in 1941. This has left some questions in the minds
of geneticists as to the purity of the spotted lines. On the other
hand, since the Tennessee Walking Horse breed is a performance
breed, the spotted horses who also exhibited the necessary gaits and
were able to pass ON these gaits, have been incorporated into
the breed registry.