I went to see a dobe puppy the other day and it had a white stripe on its chest, is this allowed or is it classed as a serious fault in the show ring.

The standard says that white markings of any kind are highly undesirable. So yes, it would be a very serious fault in the show ring.

Hi guest on a dobermann it is a serious fault as they should be black and tan only or liver, but no white anywhere.  It would be okay as a pet but not for showing. A dobs markings if black they should have tan above the eyes around their mouth and under the jaw with a black triangle, tan on chest and running down legs front and back and tan under the tail.

If the white patch or stripe is quite small, it can disappear as the pup grows.  This is because pigment cell migration is not complete at birth and can continue for weeks, months or even years in some dogs.

Julie