I think for a microwave to have any effect on a seed, the seed would have be put INSIDE and zapped. That would be as likely to sterilize the seed as cause genetic mutations. Most genetic mutations aren't all that great. They range from not noticeable to lethal. Only in rare cases is the mutation useful to the organism. Using diluted herbicides would be a more efficient method of causing a mutation.
Side note.
I thought Loch Ness Monster would make a great name for a plant. I went directly to the data base. One daylily! And one Hosta with a corrupted spelling (Lochness). I think a really dark bloom on a water iris would work better. Or purple or maroon foliage in a water plant.