You're right, it is done. I worded my comment carefully to leave room for this because it's hard to prove a negative, but I stand by my statement, specificay in refuting the implication from the original comment: we aren't haphazardly blasting plant genome with radiation, at scalr, and guessing it's safe enough to feed to the world. I don't have numbers but GMO crops today are by and large the result of non-radiation genetic engineering.