General Discussion
In reply to the discussion: Neil deGrasse Tyson Tells GMO Critics to "Chill Out" [View all]mike_c
(36,281 posts)The usual method is to grow bacteria in the presence of herbicide at varying dilutions until some colonies evolve resistance. Those colonies are selected, taken through more generations of selection to strengthen the trait, then the gene or genes conferring resistance is cloned for insertion into the target plant's genome.
The point is that there is nothing "unnatural" about the process. It works because artificial selection on bacteria screens the evolution of resistance quite effectively, and because there are very few genetic barriers to recombination once the relevant gene is in hand. But the bacteria evolve resistance quite naturally when challenged by exposure. We use exactly the same methods to screen for bacterial drug production, or for strains that will mitigate pollution.
Granted, this isn't what you likely meant by "selective breeding," but that's only because the methods applicable to asexual prokaryotes are different that those you're likely accustomed to for sexually reproducing eukaryotes.