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GENETIC ENGINEERING. Genetic engineering involves the directed alteration of an organism's DNA (deoxyribonucleic acid)—that is, its genetic material. This technology has been applied to microbes, plants, and animals, and consequently used to modify foods, animal feedstuffs, and food-processing reagents.

Domestication and improvement of plants and animals for agriculture initially relied on identification of individuals with desirable characteristics from among natural populations. Applying knowledge of genetics to the breeding of plants and animals resulted in more rapid progress and remains vitally important to agricultural development. Traditional breeding, however, is constrained by the boundaries of sexual compatibility, which limits the choice of parents that can be used as sources of genes and traits to improve a specific crop or animal to those that can produce progeny through sexual reproduction. Genetic engineering expands the source of genes that can be used to modify the characteristics of plants and animals.

Technology of Genetic Engineering

Genetic engineering requires three fundamental technologies: the ability to isolate and modify the DNA of specific individual genes; an understanding of the mechanisms that regulate how genes function and how these can be manipulated; and the capacity to transfer genes into an organism. These have all been developed following the discovery of the structure of DNA in 1953. Genetic engineering of microbes was first reported in 1973, followed in the next decade by similar achievements in plants and animals. Because DNA is the genetic material in all organisms, genes for genetic engineering can be taken from any source, or even synthesized. Modification of genes may be necessary, particularly in regions that control how they operate, in order for the genes to function effectively in the recipient organism. Agrobacterium tumefaciens, a bacterium that transfers DNA into plant cells as part of its normal life cycle, is used commonly to transfer genes into plants, although other methods such as the "gene gun" also have been developed. Genetically engineered plants are technically "transgenic organisms," as they contain transferred genes. However, they are frequently referred to as "genetically modified organisms," or GMOs, and the products derived from them are described as "genetically modified," or GM foods. These terms can be confusing, as essentially all cultivated plants have been genetically modified through breeding and selection—for example, the many varieties of cultivated onions possess numerous qualities that distinguish them from each other and especially from the wild onions from which they originated.

Application of Genetic Engineering in Agriculture

The first genetically engineered crops were planted on a large scale in 1996. By 2001 more than fifty million hectares were planted worldwide with transgenic crops. The first generation of these crops has been altered in ways that improve the efficiency of crop production by modifying the tolerance of plants to herbicides and insect pests. Broad-spectrum herbicides are able to kill almost all plants. A prerequisite for using chemicals to control weeds in a crop is that the crop itself must be resistant to the herbicide. Genetic engineering has been used to develop plants (specifically soybean, canola, corn, and cotton) with resistance to two broad-spectrum herbicides, glyphosate and glufosinate, which are sold under the trademarks Roundup and Liberty, respectively. Glyphosate-tolerant soybeans have been adopted rapidly in some countries, notably the United States and Argentina, and accounted for approximately 46 percent of the soybean acreage worldwide in 2001. Herbicide use has not declined in these crops but the specific herbicides that are used have changed.

Insect pests can damage crops during the growing season and also after harvest. A variety of methods, including cultural practices and insecticides, are used to control insect damage. Genetic engineering has provided novel approaches to this problem. The bacterium Bacillus thuringiensis (Bt) produces proteins that are toxic to some types of insects, and Bt spores have been used as insecticides for decades. Genes encoding Bt toxin proteins have been isolated, modified so they function in plants, and transferred into crop plants including corn, potato, and cotton. These engineered Bt crops are more resistant to such insects as the European corn borer, Colorado potato beetle, and cotton bollworm than are their nonengineered counterparts. The introduction of Bt cotton has resulted in reduced use of insecticides on this crop in some regions of the United States. Growers of Bt crops are required to plant a portion of their acreage with varieties that do not carry the Bt gene, in an effort to delay the development of insect populations with resistance to Bt toxins.

The Flavr Savr tomato, developed in the 1980s by Calgene, a biotechnology company in California, was the first food produced from a genetically engineered plant. These tomatoes ripened more slowly and had an extended shelf life. However, for a number of reasons—including production problems and consumer skepticism—this product was not a commercial success and was withdrawn in 1996, after less than three years on the market. Melons and raspberries have also been engineered to have delayed ripening but have not been produced commercially. Transgenic papayas with resistance to ring spot virus also have been developed. These were grown successfully in Hawaii, where the papaya industry was devastated by this debilitating disease. A similar approach was used to produce virus-resistant summer squash and against other viruses affecting a wide variety of foodstuffs.

The first generation of transgenic crops for the most part were designed to improve the efficiency of crop production, an ongoing objective for genetic engineers. Additionally, the techniques of genetic engineering can be used to alter the nutritional composition of foods. The transfer into rice of three genes that function to produce beta-carotene in the seed resulted in "golden rice." Once consumed, beta-carotene can be converted to vitamin A, the degree of this conversion being dependent upon a number of factors that relate to the source of the beta-carotene, the diet, and the individual consumer. In less-developed countries, vitamin A deficiency is widespread among those with a restricted diet, and is responsible for increased mortality and blindness in children. Although the efficacy of transgenic rice in reducing disease has not been established, it demonstrates the potential use of genetic engineering for nutritional enhancement in many crops. Other applications of genetic engineering of animal and human foods include removing allergens from foods such as peanuts, increasing the level of essential vitamins and nutrients in foods, and producing foods possessed of vaccines and other beneficial compounds.

Genetically engineered microbes also are used to produce proteins for food processing. Chymosin (or rennin), an enzyme used in cheese production, traditionally is obtained from the stomach of veal calves. However, the gene encoding this enzyme was transferred into microbes, and the enzyme now can be produced in bulk by purifying it from large microbe cultures. Chymosin prepared from transgenic microbes has more predictable properties than the animal product and is used to produce more than fifty percent of hard cheeses in the United States. Other enzymes used in food processing are produced by similar methods. For example, bovine growth hormone (BGH) is produced in large quantities from transgenic microbes and is given to cows to increase milk production.

Regulation of Genetic Engineering

In the United States, three federal agencies—Food and Drug Administration (FDA), Environmental Protection Agency (EPA), and Department of Agriculture (USDA) —are involved in regulating transgenic crops. Similar systems are in place in other countries as well. Companies that have developed this technology generally are supportive of the current regulatory framework. Nevertheless, the development of transgenic crops and the introduction of foods that contain products from these plants in the 1990s generated tremendous controversy, notably in Europe. Proponents of genetic engineering have argued that the addition of one or two well-characterized genes into crop plants that have a history of safe use is unlikely to affect materially the properties of these plants. Opponents suggest that this technology has not been tested adequately and the public should not be exposed to unknown and unnecessary food-based risks.

Safety concerns include the possibility that this technology will reduce the nutritional content of foods and introduce novel allergens or other toxins into foods. Opponents have sought more extensive testing and mandatory labeling of products that contain genetically engineered foods so that consumers can choose whether or not to eat such items. The impact of transgenic crops on the environment also has been questioned. Pests are likely to develop resistance to toxins produced by transgenic plants, raising doubts about the sustainability of this approach. However, transgenic technology also has the potential to reduce the use of chemical pesticides for crop production, which most regard as a positive development. Transfer of genes from engineered crops to other plants might also occur—for example, making weeds resistant to a specific herbicide or expanding the range of a plant so that it can grow in new locations.

This new technology also brings forth social, economic, and ethical issues, many of which are reflected by a wide political debate. One subject of concern is that most of the technology enabling genetic engineering of crop plants is controlled by a small number of companies. Much of this control is achieved through ownership of intellectual property, such as patents on genes, methods to produce transgenic plants, and the plant material that is the basis for crop improvement. Companies that manage agricultural inputs, such as seeds, pesticides, and fertilizers, as well as food processing and retail operations, function increasingly on a global scale. Opponents of globalization have criticized genetic engineering as one factor that is contributing to this trend and have expressed concern that both farmers and consumers will have limited choice in who supplies their needs. Opposition to genetic engineering also has come from religious groups who believe that tampering with genes in this way is unnatural—that is, inconsistent with the divine domain of nature—and should not be allowed.

Development of methods to genetically modify plants that extend beyond the limits of normal sexual reproduction has the potential to change many aspects of food production. Some of the first generations of products of this technology were adopted readily by most farmers but, as with other new technologies, there are many opponents. If this technology eventually receives widespread acceptance, it is likely that genetically engineered products will be found in almost everything that humans and domesticated animals eat.

See also Additives; Agronomy; Biotechnology; High-Technology Farming; History of Food Production.

Peter Goldsbrough