July 13, 2009
An Herbicide Used To Protect Corn Also Enhances Its Nutritional Value
By Michael D. Shaw
The term “sustainable agriculture” seems to have nearly as many definitions as it does proponents. The University of California Davis—a leading ag school—emphasizes three main goals: environmental health, economic profitability, and social and economic equity.
The Union of Concerned Scientists holds that “Sustainable agriculture can provide high food, feed, or energy crop yields without destroying the environment or undermining current productivity. Farmers who take a sustainable approach substitute knowledge for pesticides and fertilizers.”
Wes Jackson, of the Land Institute, coined the term, but believes that agriculture is inherently destructive, flying in the face of most historians who credit agriculture for being the basis for civilization as we know it. Jackson claims success in more or less letting his prairie land ecologically adapt itself into growing crops without removing the so-called ecological capital of the soil. This sort of prattle garners him many celebrity friends, and not surprisingly, he is also against capitalism, even if he is not above accepting grants and donations from plenty of folks who made their money that way.
Strangely absent in most treatments on sustainable agriculture is much concern with actually feeding people—especially poor people.
No doubt, pressure from agricultural environmentalists has forced suppliers to come up with better and safer pesticides and herbicides. One such product is the herbicide mesotrione, sold under the trade name Callisto. Mesotrione was first EPA registered in 2001, and is safe and environmentally friendly enough to not even merit a mention by the Pesticide Action Network—a group that is not overly sympathetic to the ag chemical industry.
As it happens, the development of mesotrione derived from a scientist observing that weeds did not grow around a bottlebrush plant near his home. He determined that the natural herbicide was the chemical leptospermone, and further work led to the synthesis of mesotrione, a closely related compound, but one that is a more potent herbicide.
Mesotrione is currently labeled for pre-emergence and post-emergence control of broadleaf and grass weeds in corn (maize). Corn is one of the few vegetable sources of zeaxanthin—a carotenoid—said to be protective against the common eye disease of macular degeneration—a leading cause of blindness.
Inasmuch as mesotrione’s mechanism of action interrupts essential carotenoid biosynthesis in the weeds—although corn can withstand this—researcher Dean Kopsell and team examined whether mesotrione would have some impact on the accumulation of carotenoid nutrients in the developing corn kernels.
Their work, entitled “Increase in Nutritionally Important Sweet Corn Kernel Carotenoids following Mesotrione and Atrazine Applications” was web-published on June 19, 2009 in the Journal of Agricultural and Food Chemistry.
Three varieties of sweet corn plants were exposed to mesotrione and a combination of mesotrione and atrazine (an herbicide often used in a mixture with mesotrione). The corn varieties or cultivars tested have the exotic trade names Merit, Temptation, and Incredible.
Carotenoid assays were were run on mature plants, harvested at 45 days (Temptation) and 56 days (Merit, Incredible) after treatment, and results were compared to an untreated control group. In virtually all cases, carotenoid levels increased in the treated corn. In the group treated with the combination of mesotrione and atrazine at an early stage, the levels of lutein and zeaxanthin jumped by more than 15 percent.
The authors hypothesize that this effect may be due to the plants up-regulating the production of these carotenoids, in response to a temporary stress from the mesotrione.
Kopsell et al. note that these results further emphasize the ability to enhance valuable phytochemicals in crop plants through careful management of cultural growing practices.
If the mission is the feeding and better health of a hungry world, Kopsell’s approach sure makes more sense than Wes Jackson’s.