A long time ago, in my old Mediterranean tiny country, I successfully did some
grafting of apricot, plum, peach and nectarine scions onto (bitter) almond seedlings,
which was the norm to go. Besides that, which I never did, other fruit species
including grapes and figs, the norm was to graft onto a (wild/better) root stock
of the same exact species.
As an example, I have read somewhere that because of an some accidental
European grape root ailment, introduced from USA, all those expensive
French wine-vines (to the French dismay) MUST have (of all places)
an American grape root stock!
Re bitter almonds: As a young kid, I also used to love eating the still green
immature (~1") fruit, tender skin and shell and all, less the bitter
(still a white skinned transparent jelly-like) kernel. They had a somewhat
pleasant mild sour taste to it. It has been quite a while from that experience,
and oh, I do long for those good old days...
Also, almonds are magnificent spring blooming trees.
The sweet expensive almonds that one usually buy from stores, is a
variant of the (wild - I think?) bitter ones. The kernel is just sweet.
.