North American Fruit Explorers mailing list at ibiblio

["Lon J. Rombough" <lonrom@hevanet.com>]

Depends a lot on where the seed source came from, as well as if it was pure.  I have seen natural hybrids of fusca with domestic apples, so who's to say the FB susceptibility wasn't introduced.  
In any case,  variation in many wild species is so common that differences in FB resistance in the wild Malus fusca species wouldn't surprise me.  It just points up the value in screening a collection of material from difference sources/locales to find the best, if it is to be used as a rootstock.  It's a very widespread species, going quite far north, clear up to Alaska, so there is bound to be lots of variation worth testing.
-Lon Rombough
Grapes, writing, consulting, my book, The Grape Grower, at http://www.bunchgrapes.com  Winner of the Garden Writers Association "Best Talent in Writing" award for 2003.
On Apr 10, 2005, at 8:36 AM, Philip Stewart wrote:

Not all Malus fusca is fire blight resistant...though
there are certainly very resistant individuals,
susceptible trees are not terribly uncommon as well. 
If I recall, Jim Cummins (or maybe some one else)
tried M. fusca in the Geneva rootstock breeding
program, and the results were not especially
inspiring. I wish I could remember, but I think he
said 25% of seedlings were FB susceptible.