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Because tomatoes are one of the world's most popular vegetables, they have benefited from a long history of genetic improvement that continues in the transgenic age. Lycopene, a naturally occurring constituent of tomato, is a nutritional factor related to Vitamin A. Tomato varieties with transgenically enhanced lycopene content are under investigation. Another trait of interest is delayed ripening. Tomatoes that ripen slower can remain on the vine longer and develop improved flavor, compared to commercial varieties that are picked at the green stage. The Flavr-Savr® tomato, one of the earliest approved transgenic crop varieties, was a delayed ripening variety. Because the trait was incorporated into a variety that performed poorly otherwise, it was not a commercial success. For more information on transgenic tomato research, see http://www.ars.usda.gov/is/

Salty soils are an increasing problem in many parts of the world. Many crop plants, including tomatoes, are killed by high salt levels in soil and irrigation water. The development of a salt-tolerant tomato offers the possibility that tomatoes could be grown on land that was previously unavailable for agriculture. Scientists (Zhang and Blumwald, 2001) at the University of California and the University of Toronto have developed a tomato plant that is able to tolerate high levels of salt and that holds the salt in its leaves, so the fruit will not taste salty. It will take an estimated three years before salt-tolerant tomatoes are available commercially. A story on the potential benefit of this new trait in tomatoes is available at http://www.guardianunlimited.co.uk/international/story/

Improved nutritional content and delayed ripening are transgenic traits of interest in tomatoes. Source: USDA

Two tomato plants artificially inoculated with bacterial speck disease. Plant on left has been genetically engineered with a gene for resistance to the disease, and plant on right is a susceptible, non-engineered variety. Source: Dr. Steve Tanksley, Cornell University.

Developing kernels of rice. Source: USDA

Golden Rice
Millions of people in the world suffer from Vitamin A deficiency, which leads to vision impairment and increased susceptibility to diarrhea, respiratory diseases, and measles. Rice is a staple food in many countries, particularly in Asia, but does not contain Vitamin A or its immediate precursors. By inserting two genes from daffodil and one gene from a bacterial species into rice plants, Swiss researchers have produced rice capable of synthesizing beta-carotene, the precursor of Vitamin A (Ye et al., 2000). This rice variety is now being crossed into adapted varieties, with field tests possible in a year or two.

Canola is a major oilseed crop. Transgenic research has focused on improving the nutritional quality of canola oil by enhancing the Vitamin E content or by modifying the balance of fatty acids.

Nutritionally improved oils are the goal of transgenic research in canola.

Improved Turfgrass for Lawns and Recreational Areas
There are a number of environmental concerns associated with the current use of turfgrass. These include

  • the amount of chemicals applied (fertilizers, herbicides, fungicides, and even green dyes);
  • the large quantity of water required to keep lawns healthy, especially in the West;
  • the energy required to mow lawns.

New transgenic turfgrass varieties will address some of these concerns by incorporating genes for herbicide tolerance, disease and insect resistance, reduced growth rates (meaning less mowing), and tolerance to drought, heat, and cold. The first such product on the market will most likely be Roundup Ready® varieties of Kentucky bluegrass, creeping bentgrass, and buffalograss. Weed control in lawns of these varieties can be accomplished with the herbicide Roundup, which is more environmentally friendly than currently used herbicides like 2,4-D.

Plant-based Vaccines
Food crops engineered to produce edible vaccines against infectious diseases would make vaccination more readily available to children around the world. Because of their palatability and adaptation to tropical and subtropical environments, bananas have received considerable research attention as a vehicle for vaccine delivery. Transgenic bananas containing inactivated viruses that cause cholera, hepatitis B, and diarrhea have been produced and are currently undergoing evaluation.

A disease-resistance trait, an anti-pest trait, and a herbicide-resistance trait are all being pursued, but no commercial varieties are now on the market. White mold (Sclerotinia) is a serious problem for sunflower producers in some areas. Resistance to this disease would expand the area in which sunflowers can be grown and might improve yields in areas of current cultivation. A commercially available cultivar is not expected before 2005. Resistance to the Argentina looper, an insect that eats sunflower leaves, is also being investigated. Some research has been done on developing sunflowers that can tolerate being sprayed with the weed killer Roundup. This trait would allow a farmer to spray his field for weeds while not killing the crop. For more information on transgenic sunflower research, see http://www.checkbiotech.org/root/

Field of sunflowers. Source: USDA.

Coffee and Tea
Decaffeinated coffee is now made by treating coffee beans to remove the caffeine. One method uses organic solvents to extract the caffeine, which causes some consumers to be concerned that residues from the solvents will remain in the coffee they drink. Other methods are criticized for removing some of the desirable, flavor-producing components along with the undesirable caffeine. Two scientists in Hawaii and Scotland have identified different genes that lead to the production of caffeine in coffee beans and tea leaves. If these genes can be "turned off" in some plants, coffee and tea trees could be developed that would produce naturally decaffeinated products with full flavor and aroma.

The harvesting of coffee beans now requires many passes through the orchards because the beans ripen at different times. A scientist in Hawaii is developing a method for making all the beans ripen at the same time so that harvesters could pick all the beans during one pass through the orchard.

Integrated Coffee Technologies Inc. http://www.integratedcoffee.com/AboutICTI.htm in Hawaii is pursuing both the decaffeination and the controlled ripening of coffee. The patent for the caffeine gene is available at
. The patent for the ripening gene is available at
netahtml/ srchnum.htm&r=1&f=G&l=50&s1='5874269'.
. For information on the tea caffeine gene discovered at the University of Glasgow, see Kato et al. (2000).

Coffee berries, called "beans," ripening on the tree. Source: USDA

Ripening grapes. Source: USDA

Grapes and wine
Grape vines (Vitis vinifera) are susceptible to several diseases that reduce the amount and the quality of wine grapes and table grapes or even kill the vine. Genes that confer resistance to particular diseases would reduce the cost of battling diseases in the vineyard. Researchers at the University of Florida have patented a method for producing grape vines that carry a silkworm gene to provide protection from Pierce's disease, a fatal bacterial disease that affects grapes and several other plants. A brief story on the discovery is available at http://newscientist.com/
. The patent is available at
. Information about Pierce's disease is available at http://www.cnr.berkeley.edu/xylella/.

Nicotine-free tobacco is now being grown for a projected introduction of nicotine-free cigarettes. Previous attempts to make low-nicotine products removed some of the flavor along with the nicotine. Genetically engineered nicotine-free tobacco doesn't synthesize nicotine in the leaf. A story in the Philadelphis Inquirer on this tobacco being grown by Amish farmers in Pennsylvania is available at http://philainq.infi.net/content/inquirer
. A story on some of the business aspects of the product is available at http://inq.philly.com/content/inquirer/2001/
. The Picayune Item has a story on farmers growing the tobacco in Mississippi at http://www.picayuneitem.com/archives/index.inn?loc=detail&doc=/

Tobacco. Source: Hugh Wilson, Texas A&M University

Forest trees such as poplar, aspen, and spruce have been transformed with various genes to provide resistance to insects, tolerance to herbicides, and higher levels of the commercial product. For example, reducing the lignin content of a tree can make it easier to recover wood pulp. For a range of views on the potential risks and benefits of transgenic trees, see presentations from a symposium at http://pewagbiotech.org/events/1204/index.php3#agenda. Some transgenic tree species now being tested include:

Species Trait Link to more information
poplar herbicide tolerance
insect resistance
eucalyptus herbicide tolerance
aspen reduced lignin http://www.admin.mtu.edu/urel/breaking/1999/aspen.htm
sweetgum herbicide tolerance
white spruce insect resistance

Transgenic trees probably will not be commercially available until at least 2006. Source: Kaiser, J. 2001.

Page last updated : March 11, 2004

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