Sustainable Darwinian Agriculture and Organic Tomatoes
I will be reviewing another recent journal article today or tomorrow, but meanwhile we seem to have convinced someone that an evolutionary perspective is useful in agriculture. A recent book review mentions a chapter we wrote:
There is also food for thought in some of the chapters, particularly the one by R.F. Denison and E.T. Kiers on sustainable crop nutrition. This perceptive analysis raises questions about the simplistic assumptions that often underlie attempts to improve crop mineral-use efficiency and highlights areas where such attempts are likely to be useful and others where they are not. This reviewer certainly changed his thinking as a result of the ideas put forward.I doubt that the reviewer, Roger Leigh, remembers a mostly positive review I wrote of a book on long-term field experiments (mostly agricultural) that he edited over ten years ago, when I was directing UC Davis's Long-Term Research on Agricultural Systems (LTRAS) "100-year experiment." Our chapter discussed the implications of "our crops' legacy of preagricultural evolution", a topic we previously addressed in Darwinian Agriculture. For example, past natural selection for individual competitiveness may have favored more investment in roots than is optimal for maximum grain yield. On the other hand, human goals like reducing nitrate loss to groundwater (an environmental problem ignored by natural selection) might call for deeper rooting than would be needed for yield alone. We also discussed evolutionary conflicts in nutritional symbioses (e.g., with nitrogen-fixing rhizobium bacteria or the mycorrhizal fungi that provide many plants with phosphorus), the topic of our current research -- watch for our review in Annual Review of Ecology and Evolution.
Our recent paper comparing organic vs. conventional tomatoes also has an evolutionary twist...
Although it's only mentioned briefly, especially in the popular press coverage, the original article points out that "Secondary plant metabolites such as the flavonoids function in plant defense mechanisms against herbivory...", so that "possible differences in pest pressure between conventional and organic systems might also influence levels in food crops."
These particular natural pesticides are apparently beneficial to humans, so if organic farms have more pests -- or, really, anything that triggers the defense response -- we get more of the beneficial chemicals in our tomatoes. One interesting follow-up would be to look at other defensive chemicals and see if they are also higher. The thing is, some of the natural insecticides plants make, especially when attacked by insects, are likely to be harmful to humans, rather than beneficial.