I pulled this from another location. I have read the same thing while reading articles from turkey biologists
Disease -- Turkeys will occasionally get a melanin deficiency in their beard. Melanin is the pigment that makes the beard black and sometimes the melanin production is stopped during the growth of the beard and the beard gets a blond or light colored streak across it. Usually the melanin production will pick back up and the rest of the beard will be black but the beard will always have that blond streak through it. The light-colored portion of the beard is much more brittle and weaker than the black portions and the beards will often break off at that point or stop growing. Some turkeys suffering from this will have completely blond beards.
