North American Fruit Explorers mailing list at ibiblio

["alden@waldenwinds.com" <alden@waldenwinds.com>]

http://capitalhort.cas.psu.edu/ResearchThings/BlackberryTalk.pdf

is a 2006 report from Penn State.
They grew-out 13 different cultivars of blackberry.   Thorny, Smooth, 
Primocane.
And the winner is....   Cacanska.   Produced 3x as much fruit as some other 
better-known ones.

Thornless: . Apache
. Cacanska .    Doyle's Thornless . Navaho . Ouachita(2) . TripleCrown
Primocane Bearing: . PrimeJan(2) . PrimeJim(2)
(both are thorny)

I only count 8 varieties....I guess they counted some varieties twice to get 
thirteen.
Charlie Paradise, Massachusetts