I followed the discussion about alfalfa and GMO this last winter, and I disagree with the conclusions that ATP members reached. Further, GMO alfalfa is in very limited production and the odds are that the inexpensive alfalfa at my local store is not in fact GMO.
Roundup is greatly misunderstood. It affects all plants that it contacts because it overfeeds them and kills the plants. A scientist at Purdue University was trying to create a fertilizer, but it killed all plants that it contacted. Later he and another scientist who was trying to create a herbicide, joined forces and created Roundup.