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Genetically Modified Crops

Developments in transgenic technology require a continuing effort to inform the public.

Much has happened since the February 2000 issue of From The Ground Up provided an introduction to genetically modified organisms (GMOs) and transgenic technology. There are exciting breakthroughs in research and new genetically modified (GM) crops, but at the same time public debate about GM crops and foods has intensified. Clearly, the future of transgenic technology depends on consumer acceptance of its products. There is a need for public education about GM crops and foods: how the technology works, what it can do, what are the real benefits and potential risks.

A three-year grant awarded to Colorado State University and the University of Nebraska through the U.S.D.A. Initiative for Future Agriculture and Food Systems funds a project to provide information and public education about transgenic crops and foods. The project is described in more detail inside this issue, along with an update on GM crops: their current status, new products in development, and emerging issues of concern. For information on t he nuts-and-bolts of transgenic technology, visit our web site at

by Sarah Ward
Associate Professor of Plant Breeding and Genetics
Department of Soil and Crop Sciences

Transgenic Plants for the Future

Will the next generation of genetically modified crops improve public acceptance of biotechnology?

Critics of transgenic technology claim that genetically modified (GM) crops currently in commercial production only benefit producers and a few large agricultural corporations and offer nothing to the general public. While it can be argued that some changes in crop production associated with transgenics do benefit the consumer - reduced pesticide applications with Bt cotton, for example - it is true that the first GM crops to reach the market were not developed to provide direct benefits for consumers. New transgenics now in development, however, could change this dramatically, with crops being genetically modified for enhanced nutritional or other health benefits. Exciting current examples include golden rice, cavity-fighting apples, and antioxidant tomatoes, and edible vaccines in bananas.

Rice plants

Golden rice
Although rice is a staple in the diet of much of the world population, the grain is low in several key nutrients, including vitamin A. Golden rice has had two daffodil genes inserted coding for the enzymes which produce beta carotene. This is then converted to vitamin A in the human body. The presence of the beta carotene turns the rice grain yellow, hence the popular name for this GM crop. U.N.I.C.E.F. estimates that 124 million children around the world suffer from vitamin A deficiency, resulting in half a million cases of childhood blindness annually. Because the current version of golden rice does not deliver the full daily requirement of vitamin A, consuming golden rice will not solve this problem alone. However, it will make a contribution to a better diet for many people if supplies are made available at an affordable price. Golden rice arrived in the Philippines in January 2001, where plant breeders at the International Rice Research Center are now developing locally adapted strains for distribution to farmers.

Cavity-fighting apples
Medical researchers at Guy’s Hospital in London and scientists at the Horticultural Research Institute in Kent, U.K., are developing apples with a bacterial gene coding for a protein which prevents decay-causing bacteria from attaching to teeth. Results to date suggest that eating the GM apples could significantly reduce cavity formation.

Antioxidant tomatoes


Flavonols are powerful antioxidants with the ability to neutralize harmful tissue-damaging molecules circulating in the body. Some foods, such as onions and tea, are naturally rich in flavonols, and several current research projects involving GM crops aim to increase beneficial antioxidant levels in other food plants. Scientists at Unilever have inserted a petunia gene into tomatoes which increases flavonol production up to 78 times over the relatively low levels normally found in the fruits. Taste is not affected, and 65% of the flavonols are retained when the tomatoes are processed into paste. Researchers have coined the term “functional foods” for items such as this, where conventional breeding or transgenic technology have enhanced levels of compounds in plant or animal products with health benefits beyond basic nutritional requirements.

Edible vaccines
Several crop species have been genetically modified to produce plant-based vaccines, which can be administered by consuming the plant product. One of most promising plant-based vaccines confers resistance to the liver disease hepatitis B through eating a dried GM banana chip. Researchers at the Boyce Thompson Institute at Cornell University have also modified tomatoes with a key gene from the hepatitis B virus, and found that small quantities of processed or dried tomatoes produced antibodies against hepatitis B when consumed. A dose of tomato- or banana-based hepatitis B vaccine costs around 2 cents per dose, less than 1% of the cost of a conventional hepatitis B vaccine.

Another frequent criticism of transgenic technology is that GM crops have not resulted in increased food production, especially in developing countries. New transgenics now in development could help solve the problem of feeding a world where the human population keeps expanding but usable agricultural land does not. Among examples recently in the news are salt-tolerant tomatoes and iron-pumping rice.

Salt-tolerant tomato
Researchers at the University of California at Davis have produced a GM tomato which can grow in soil irrigated by water containing up to 200 millimolar sodium chloride, 50 times the salt content normally tolerated by unmodifed tomatoes. The tomato contains a gene from thale cress (Arabidopsis thaliana) which segregates sodium ions from intracellular water for storage in vacuoles. Fruit from the salt-tolerant tomatoes tastes normal -- the salt is stored in vacuoles in the leaves.

Iron-pumping rice
Iron-deficient alkaline soils are common in many of the world’s arid regions. Cereals such as corn and barley release an iron chelator known as deoxymugineic acid (DMA) when grown in such soils. DMA binds the iron and transports it across the root membrane, enhancing uptake by the plant. Rice normally produces very small quantities of DMA, making it an ineffective scavenger of iron in alkaline soils. Japanese researchers have transformed rice plants with two barley genes coding for enzymes which synthesize DMA. The GM rice plants have greatly enhanced DMA production and iron uptake, and yield up to four times more than non-GM rice when grown in iron-poor soils.

Public concern about transgenic technology in the U.S. and international opposition to it abroad, especially in Europe, have impacted markets for GM crops grown in the U.S. The future of GM technology depends on consumer acceptance of its products. Will the potential benefits offered by the next generation of GM crops be sufficient to persuade a skeptical international public?

by Sarah Ward
Associate Professor of Plant Breeding and Genetics
Department of Soil and Crop Sciences