In article , Salty Thumb
writes:

As a side note, I read that sometimes Black Walnuts are grafted onto
other root stock (or vis versa?), so you may not have any problems or
have less severe problems than cited for pure black walnuts.

Engish walnuts are grafted onto Black Walnut root stock. Black Walnut
is resistant to Oak Root Fungus, while the English is not. This was
a discovery of John Bidwell, the founder of our city in Northern Calif.
a great walnut growing area.
just a bit of trivia.......
Emilie
Norcal