Trying to work out what's going wrong in the cases this article describes, such that the principle "you can't patent something that exists" apparently doesn't apply. Is it that an independent breeder develops a certain strain, say red salad, and then a big company makes a modification to that strain, and patents the modification, such that the independent breeder is prevented somehow from continuing to develop red salad? That still doesn't make perfect sense to me but it makes more legal sense than "company got patent on what you already made, you can't make it anymore", which is just not how patents work.