I think that the first "forage rape" bred was Tyfon, back in the 70s by a Japanese researcher trying to breed nutritious brassicas for dairy cattle that would be low in mustard oil so as to not taint the milk. The seed parent was the ancient Stubble Turnip, pollen parent was a modern Chinese Cabbage...end result was a sterile mule exhibiting full hybrid vigor with BIG tender mild leaves called Tyfon. I think it is the only forage rape sold in veggie seed catalogs, the others have to come from farmers' supply houses like Welter Seed and Honey Co. As far as I know, none are GMO, just the result of very clever crosses of brassicas....I think it was either Pasja or Appin that resulted from crossing a turnip with mizuna. I think Dwarf Essex was bred from a kale. All are very cheap by the pound from Welter for gardeners to share as classic winter crops for central and south Florida, summer crops in cold winter areas. All are very mild raw or cooked, perfect for people who don't like strong bitter greens.....Bonar is VERY mild...even my Dad liked it raw!

http://www.welterseed.com/