That's one way to get biodiversity, but you can also generate more diverse populations in the lab and plant them in the field. You can also seek out natural reservoirs of variation in the form of wild or land race cultivars, and introduce favorable traits into your elite commercial cultivar. I work in this field. This is where our food supply is going, where it has to go if we are to feed ourselves in a century, when changing conditions mean the crops being planted today will not achieve the same yields in the future.