GMO's, as in Genetically Modified Organisms have only been around since the 1980's. These are different than hybridized plants. Hybridized plants are plants that have been very carefully cross-bred. In facts, most of what we eat is from a plant that has been crossbred at some point. Hybridization just speeds things up. The different foods listed above are just the results of breeding, either through traditional cross breeding or hybridization. (except maybe the corn) Cross breeding plants in its simplest forms is similar to cross breeding animals. Farmers use breeding to improve their plants, just like they would their livestock.

GMO's on the other hand are done in a lab. They're actually doing things like gene splicing, be able to take genes from a bacteria and integrate it into a plant to obtain desirable traits, etc. In the grand scheme of things, not many of the U.S. crops are GMO. It's mainly corn and soybeans. The issue lies in the fact that most processed foods contain either corn or soy in some form. Most cereal grain farmers are against GMO's as they mostly save seed, meaning the best portion of their harvest will be saved to use as seed for next year. You can't save seed with GMO's, as it's written into the contract with the seed company that way. My neighbor planted a variety of oats call Owatonna in 1977. He's been saving seed every year. It's become a "landrace" strain by today, acclimated to his soils, his rainfall, etc. Another farmer could have planted the same variety in the same year, but today, they would not have the same oats.