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[ The maize story - from inedible pod to top U.S. crop ] [ Traditional breeding compared to transgenic technology ] [ Chemical pesticides/herbicides compared to transgenic technology ] [ Organic farming compared to transgenic technology ] [ Food Additives Compared to Transgenic Technology ] [ A diversity of views ] | |
— The Maize Story - from Inedible Pod to Top U.S. Crop — Seven thousand years ago, an ear of corn resembled a segmented green bean the size of an index finger. The kernels were each enclosed within a pod that humans could not digest, and each plant produced multiple small ears and tassels that were challenging to harvest. Domestication through traditional breeding has transformed maize from an inedible grass to the top grain-producing crop in the U.S., generating $30 billion annually from about 80 million acres. Early natives of Southern Mexico initiated the dramatic conversion of maize into its modern form by selectively cultivating plants with a thin-skinned pod, more rows of kernels, and fewer, larger ears. Maize breeding continues today, using such traditional approaches as well as the tools of modern genetics and molecular biology. The primary goal, as in ancient times, is to increase the productivity and nutrient value of this wholesome grain. [ ^ TOP ^ ] — Traditional Breeding Compared to Transgenic Technology — Traditional breeding has done a great job of dramatically improving corn production over the last 10,000 years. But transgenic technology offers a new approach-one that has the potential to carefully introduce desired traits from either a different corn variety or a different plant species, while making it easy to exclude less appealing traits. To generate new corn varieties, a traditional breeder must cross and re-cross plants over several generations, watching closely for traits considered advantageous. The new variety must then be grown under a diverse set of conditions to see whether the cross introduced any disadvantageous traits at the same time. Transgenic technology allows researchers to introduce a gene or cluster of genes for known traits and evaluate the genes' effect in just one or two generations, with certainty that no other traits were introduced at the same time. Thus, transgenic technology has the potential to produce better crops with greater precision than traditional breeding. In addition, transgenic technology can introduce traits from other species - something traditional breeders ordinarily cannot do. Some of the most important transgenic crops take advantage of this, as they express genes that confer pesticide resistance or make the crop tolerant of Roundup-one of the most effective and least toxic herbicides. — Chemical Application Compared to Transgenic Technology — According to a 2001 report by the National Agricultural Statistics Service (PDF), more than half of all land used to grow corn in the United States in the year 2000 was treated with non-organic pesticides. In that same year, 23% of the cornfields were planted with biotech varieties designed for pesticide resistance, permitting farmers to apply less chemical pesticide on those fields. For soybean fields in 2000, 54% of the fields were planted with herbicide-resistant biotech varieties (eg., “Roundup-ready” soybeans). This allows farmers to use biodegradable herbicides such as Roundup rather than other, more toxic weed-control chemicals. Researchers have shown that the use of biotech varieties has in fact reduced insecticide and herbicide use around the world. Studies by the National Center for Food and Agricultural Policy (NCFAP) found that in 2003, the eleven biotech crop varieties adopted by U.S. growers reduced pesticide use by 46.4 million pounds per year. In a 2003 book, The Environmental and Economic Impacts of Agbiotech: A Global Perspective, Nicholas Kalaitzandonakes compiled a variety of research papers on the subject and found that, overall, the use of pesticide- and herbicide-tolerant varieties of crops reduced the application of chemical pesticides and herbicides; decreased environmental harm; and increased agricultural production. In the United States, adoption of herbicide-resistant soybean production was shown to reduce environmental damage by up to 50 percent throughout the Midwest. [ ^ TOP ^ ] — Organic Farming Compared to Transgenic Technology — Organic farming has become very popular in the United States and Europe over the last decade. Although this approach can reduce chemical fertilizer, pesticide and herbicide use, organic farming can only impact the small amount of acreage now dedicated to that use. And organic approaches, which are extremely labor intensive, are unlikely to become the modus operandi for large areas of land in the United States. Unlike organic farming, transgenic technology has the potential to reduce pesticide and herbicide use on large-scale farms. Thus, plants designed to control pests and resist herbicides have the potential to be more environmentally beneficial than organic farming because they may reduce use of these chemicals on a vaster amount of acreage. Moreover, transgenic technologies can be more targeted than organic approaches. Consider the following: Organic corn producers spray their crops with a bacterium called Bacillus thuringiensis, or Bt. It's a pesticide that kills the European corn borer and the corn ear-worm in a very specialized way: by boring a hole in the worm's gut. Bt is organic because it's a bacterium, not a chemical, and it's harmless to humans. But spraying with Bt has some downsides: the Bt spray can be carried to neighboring plots by wind; Bt has the potential to affect other species in the Lepidoptera (moth/butterfly) family; and Bt spray can lead to Bt-resistance in the corn ear-worm, so that the spray will no longer be effective. Enter transgenic Bt corn, which contains the specific gene that creates the protein that bores a hole in the gut of the corn earworm. Unlike the organic process, the Bt doesn't get sprayed - the protein is simply part of the corn plant. When corn earworms take a bite, they die. And, thus far, Bt corn has produced less Bt resistance than Bt spray does. In a 2005 paper in Proceedings of the National Academy of Sciences, researchers saw no evidence of Bt resistance over an eight-year period of growing Bt cotton. And although there has been much press coverage of potential harm to monarch butterflies, the studies have been inconclusive (link to page 4f) and fail to mention that Bt sprayed on organic corn likely has the same effect. [ ^ TOP ^ ] — Food Additives Compared to Transgenic Crops — Throughout history, new foods have been introduced into the human diet. After the discovery of the new world, Europeans adopted tomatos, potatos, corn, beans, chocolate, and peppers from the Americas while Native Americans adopted wheat, apples, beef, chicken, pork and rice from the “old world." Foods have also been enhanced by additives for a long time: Romans preserved fruit in mustard and honey (both of which contain numerous vitamins), the United States and Switzerland mandated addition of iodine to salt more than 100 years ago to reduce the incidence of goiter; and the British navy recognized that citrus fruit (vitamin C) would prevent scurvy and added limes to the diet on board ship. As vitamins were discovered in the 20th century they were added to milk (Vitamin D plus calcium), bread (B vitamins), juice, etc. in an attempt to provide a more nutritious diet. And vegetarians add yeast and other fungi to their food to provide nutritional requirements common in meats but missing in vegetables. The U.S. Food and Drug Administration (FDA) maintains a list of food additives that are “generally recognized as safe” or GRAS. A substance is GRAS when its safety can be established by a long history of use in food or when the nature of the substance and the information generally available to scientists about it is such that it doesn't raise significant safety issues. Genetically modified foods are regulated by the FDA as well as the EPA and the USDA. But the only “additive” in such foods is genes made of DNA. Because DNA is a component of virtually every food, it is considered GRAS. The protein or enzyme produced by that gene can also be considered an additive, but these proteins are usually found to be GRAS as well. Often this is because they are naturally found in other foods. For more information, read an interview with the FDA Commissioner Jane Henney at www.fda.gov/fdac/features/2000/100_bio.html. — A Diversity of Views — Genetically modified organisms provoke strong feelings in many people. But to scientists involved in transgenic plant research such as the FLcDNA project, many concerns seem misplaced. While governmental regulation is appropriate to ensure environmental and food safety, many scientists believe that society will benefit from the design of crops to promote a specific goal, such as reducing pesticide and herbicide use; improving nutritional content in the developing world (eg., golden rice in southeast Asia; or producing medicines that would otherwise be unavailable or prohibitively expensive. A case-by-case approach that weighs the benefits and risks of engineering any given plant may be best. But what are those risks and benefits? |
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© The Maize Full Length cDNA Project Contact: Virginia Walbot