Basically what they do is speed up evolution of the plants. Evolution is when a trait, should it be color, taste, smell, or anything else on a species is different accidentaly, but when that accident is a good thing, the breeders will rcognize that trait and try to keep it going by producing seeds. They then try to make sure every seed that comes out of it has that same trait (also known as stabalizing the strain). Once it's been stabalized and named, it is a new strain that might have characteristics that a lot of people would want (like blueberry). Hope this helps.