In this podcast, I talk to R. Ford Denison of the University of Minnesota. Denison is an evolutionary biologist who's interested in how to make agriculture better. The ways in which plants thrive or fail are shaped by their evolutionary history, as well as the evolution that unfolds every planting season.
We're most familiar with the evolution of resistance to pesticides in insects and to herbicides in weeds. But evolution has many other effects on farms. For example, many important crop plants, like soybeans, cannot extract nitrogen from the atmosphere on their own. They depend instead on bacteria that live inside their roots.
In exchange for fixed nitrogen, the bacteria get nutrients from the plants. It may seem like a happy case of cooperation, but the evolution of cooperation always runs the risk of cheating and deception. How plants and bacteria come to a compromise is a remarkable story that Denison and his colleagues are now documenting.
Cross section though a soybean (Glycine max 'Essex') root nodule. The bacterium, Bradyrhizobium japonicum, infects the roots and establishes a nitrogen fixing symbiosis. This high magnification image shows part of a cell with single bacteroids within their symbiosomes. In this image, you can also see endoplasmic reticulum, dictysome and cell wall.
Download: mp3 (38.5 min | 35.5 megs)