There you go then - if it's possible for mankind to make a right royal
screw-up by simply "pick 'n mixing" natural varieties, how much
greater is the potential for disaster by forcibly fooling about at the
genetic level.
Clearly there are many interactions that we do not yet understand.

The difference being that "pick-n-mix" cross breeding transfers any number
of unknown genes, whereas a GM organism would have only a very few, well
known, genes transfered.
The difference between the sledge-hammer and scalpel approaches. Which one
is best ?
Tim.