Hans,
Can you read Czech? Perhaps you should find a translator before you
continue in this thread. You should have read the link you sent (at bottom
of this message). Your link is for Temnoplodec cernoplody, not Cerny jerab.
Go to this link, which IS for Cerny jerab
http://www.001shop.cz/Cerny-jerab , then compare the picture on your link
with the picture on this link, undeniably Mountain Ash, Sorbus melanocarpa.
I think your plant has been much more known outside USA.
Approx. 1900 Michurin imported seeds (from Germany!) to Russia.
1971 Siberia has had already 4.000 ha (1 ha = 10.000m?) of Arionia
production.
Many East-Europe and North-Europe countries are producing Aronia at
plantations.
E.g. at GDR it has been the custom to graft aronia onto 1m Sorbus
aucuparia rootsstock.