I have several pear varieties, several mayhaw, a couple of quince, and one Amelanchier selection grafted onto native cockspur hawthorn(C.crus-galli).
The hawthorn understock is quite dwarfing for the pears - no fruit production yet - and it's supporting the quince and serviceberry OK - with no sign of decline after about 4-5 years.

A prune plum grafted to a Nanking cherry (tomentosa) rootstock appears to be taking for me this year- but check back in 2012 or so, and we'll see whether it's still alive, and even, if I'm so lucky, productive!

Good luck,

M

ps- "Intergenetic" is a little hard to quantify, as all combinations of non-clonal plants are by definition "intergenetic"- so a Gala apple grafted onto a Jonathon tree would be intergenetic.

Grafting a pear to an apple is perhaps "more intergenetic" and more difficult, but apparently has been done (I think an interstem is necessary, and it's not really very worthwhile); pear are often grafted to quince, however.

So the lesson might be that rootstock or understock needs to be more primitive than the scion- but I stand ready to be corrected on that assumption.

True, nearly any graft is "intergeneTic", but this refers to "intergeneRic" grafts, as in b/w 2 genera (plural for genus). Pyrus onto Malus, Citrus onto Poncirus, that sort of stuff...

The apple cultivar 'Winter Banana' is well known to be graft compatible with many pears - European and Asian - and there is a 'Superclone' selection that also supports pears with long-lived/non-declining unions.
'Fertility' pears is reputed to be graft compatible with many apples, as well.

Like Mark, I've grafted/budded Japanese hybrid plums and peaches onto Nanking cherry(P.tomentosa) rootstock; the resulting plants survived for 5 years or more - the entire plants succumbed, in both cases, not just the grafted scion part, so I can't attribute the loss to graft failure.

Lucky, I keep reading you'all mentioning superclone. I can find no reference to it on the internet other than this forum. Where is it available etc?

Robert

By the way, my prune plum on p tomentosa seems to be "OK" but hasn't added any growth for at least three weeks. Maybe it doesn't like the hot weather?

All my other grafts (on pear and apple) are quite happy and vigorous.

Seagrapes, you're right, of course. I am wondering in print just where the lines are drawn by those who understand this stuff more accurately than I. For example, some botanists, I understand, consider pears and apples to be more closely related than some other botanists, and similar questions exist in lots of other plants.

Good luck,

M

Robert,
Linked below is the patent info on the SuperClone apple - evidently it originated as a sport of 'Starking Delicious'.

Here is a link that might be useful: SuperClone apple