I was surfing on the topic of pears rootstocks and found this site which
says that "no Euro pear rootstock has enough vigor for Asian pears except
for the more vigorous OH x F clones". The result I gather is smaller fruit,
thus the prefered variety is betulifolia which is very vigorous.
Here is the site http://eesc.orst.edu/agcomwebfile/edmat/html/pnw/pnw341/pnw341.html#anchor343435
Kevin Bradley
2301 S Park St #24
Madison, WI 53713
608-256-2659