Plants/Farming Question URGENT?

Question

This is the last question I need to answer for a lab, and it's stumped me.

"What prevents farmers breeding a crop that converts all the plant tissues into the part that we utilize"

Cheers!!

Answer 1

I like to eat a plant called Allium triquetrum.  It's a relative of the onion.  All parts of the plant are edible (although the bulb doesn't taste all that great).

...and I do mean all parts.  Leaves, flowers, flowering stalk, bulb, roots.  Yum.

Answer 2

no fertilization for the next crop? that's my guess, if the question was a bit more specific i might have a better answer. Sorry.