Here's a link from Australia about chill hours, but I don't think it answers your question:

http://www.newcrops.uq.edu.au/acotanc/papers/campbel1.htm

Found the following line (but no followup):
A technique of top grafting has been performed in Taiwan for temperate pears on to tropical pears, allowing production of temperate pears in tropical lowlands of Taiwan, and earlier production.

at:

http://www.agrsci.unibo.it/wchr/wc2/ganry1.html

Found this abstract which says temperate species are being grown in Peru (tropical), but you'd probably have to buy the paper to find out what they're doing:

http://www.actahort.org/books/199/199_8.htm

And here's a slew of papers on temperate fruit in tropical areas:

http://www.actahort.org/books/199/

But it looks like you may have to do your own research.

Good luck!

Chris

Thanks Chris,

Most likely I will need to do my own research, perhaps I can talk my boss into springing for a trip to these sites to first hand research, LOL, but did find a few interesting tidbits:

The Australia article contained some nice tidbits:

"The chilling requirement of a rootstock can have an effect on the chilling requirement of the variety."

"Where a rootstock is high chill (eg. MM.111 1100 hours, Young 1992), the effect on a low chill scion variety may be less than the other way about as with pears, as the buds of the scion have had enough chill."

It is going to take awhile to go through this great site: http://www.actahort.org/books/199/

Thanks again!

My gut says that while there may be some effect, you aren't going to get something which requires a 1000 chill hours to grow in zone 8, or there'd be a lot more people doing it.

Don't know exactly what they're doing in the Peru article mentioned, but I know they can get high-chill blackberries to grow in the tropics by periodically defoliating them.