GMO's are not produced by targeted radiation in the way you have described, at least not as common practice (i.e. the GMO food you buy isn't created this way). GMO crops are generated in two ways: targeted gene modification (with deliberate modifications being made in contrast to the randomness of the radiation method you described) and crossbreeding (which has a more randomized effect but does not involve radiation).
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.
If you look at the [Wikipedia article on genetic engineering techniques](https://en.m.wikipedia.org/wiki/Genetic_engineering_techniqu...) radiation doesn't appear once.