To give you an example, in the Pacific Northwest, Jim Cook's group identified that a very serious disease of wheat, called Take-All, could be controlled by consecutive cropping of wheat, rather than a rotation cropping. After 50 years of research, this group discovered that the primary mechanism for this is the build-up of a specific group of bacteria called pseudomonas. These bacteria produce an antibiotic that actually controls the pathogen, even though it's present in the soil in high quantities.
What you see, as a result, is now these bacteria have been fully sequenced, the genes controlling the antibiotics are well understood, and you can actually detect presence of the genes in soil by using polymerase chain reaction assays. These are measuring DNA pieces of DNA in soil.
People who are measuring the DNA in soil in wheat fields are looking for rotations that keep populations at high levels, thereby suppressing the disease. All the technology for keeping this disease away from the production systems is now based on soil health, which is keeping these organisms at high levels.
You now have a rational basis for making a decision as to what crop you put in after your wheat to make sure the next time you plant wheat you don't get this disease. There are certain crops that knock those good guys down and there are other ones that raise them up. People are now using a DNA test to say this is good for us or this is not good for us.