1.Tomatoes

1.1. Conventional tomatoes

Tomatoes are cultivated in North, Central and South America, and in Europe. Ripening of the fruits is linked to production of ethylene. This triggers a series of biochemical processes involving the formation of aroma and taste properties and the production of valuable constituents (e.g. vitamins), but also hastens degradation processes responsible for the softening of the fruits.
Ripe, red tomatoes are too sensitive to endure long transport without damage. This is why tomatoes are picked green, transported under refrigeration, and treated at the destination with ethylene to trigger or accelerate the final ripening process (in the United States, for example, over 80% of the conventional tomatoes are picked in their unripened, green state). While treatment with ethylene makes the tomatoes redden rapidly, the tomato itself can never attain the aroma and flavour of one that has ripened slowly on its stem.

1. 2. The FlavrSavr® tomato

The achievement of full ripening without softness is the aim of many companies, not only in connection with tomatoes, but with many other vegetables and fruits.
Calgene set out to produce a tomato that can ripen longer on the stem and thereby attain its full aroma without getting soft, thereby enhancing its transportability and storage properties. The result was the FlavrSavr® tomato, the first genetically modified food to be granted a licence for human consumption. It was introduced into the American marketplace in 1994.
The FlavrSavr® tomato was modified in such a way that the enzyme polygalacturonase (PG), which is responsible for the tomato's softness, is no longer formed in the tomato or else only in negligible quantities, meaning that the tomato keeps longer.
The FlavrSavr® tomato differs from conventional tomatoes only in terms of the delayed ripening process. There are no differences between the FlavrSavr® tomato and conventional tomatoes as regards vitamins, protein, and mineral substances. This is true for both the first generation as well as for all subsequent generations of the FlavrSavr® tomato.

Nutrients per 100 g of tomatoes

Source: Trends in Food Science & Technology, Vol. 5, April 1994

1.3. Advantages of the FlavrSavr® tomato in comparison with conventional tomatoes

The FlavrSavr® tomato can ripen on the stem and need not be picked green and unripe as is the case for conventional tomatoes. During the ripening process on the stem, the FlavrSavr® tomato can develop not only its colour, but also its characteristic flavour properties and valuable constituents. It can be transported unrefrigerated thereby saving energy. The FlavrSavr® tomato reaches the consumer in an optically attractive state, with a fully developed flavour and firm to the cut.
The British firm Zeneca, working with scientists from the University of Nottingham, has also developed a tomato with a delayed ripening process. It is particularly suited for the production of tomato pulp: since the degradation of its cell walls is delayed, the pulp produced from this tomato exhibits the desired viscosity. With conventional tomatoes the degradation of the cell walls is prevented by heating, i.e. by destruction of the PG enzyme. However, heating also destroys the aromatic substances. The resultant tomato purée was sold by two chain stores only (selected branches of Safeway and Sainsbury's supermarkets). It was first sold on February 5th, 1996, with the GM purée outselling the conventional alternative in some stores. The tomato purée was always clearly labelled. Both stores pledged that they would always provide an alternative, conventional tomato purée alongside the GM form.
The GM tomatoes were grown in California. They were not the same as the US 'FlavrSavr®' (which is no longer produced). The GM tomatoes, which were kept apart from the conventional type, were used for the purée only, and were never put in any other products.
By March 1999, public reaction to GM foods forced Sainsbury's to announce that they would no longer stock the purée once existing stocks ran out. In July 1999, Sainsbury's removed any remaining cans from its shelves (and all other own-label products that contained materials from GM sources), following the announcement of rival high-street chain Marks and Spencer that it was now 'GM free'. Safeway's stocks of the product had run out some time before.
Overall the amount of energy required for the production of pulp from transgenic tomatoes is lower. In the United States these energy savings amount to approximately 100 million US dollars each year. Zeneca applied for a licence for the marketing of this tomato variety in accordance with Directive 90/220/EEC, via Spain in 1997. Approval is expected to be issued in the future.

2. Rice

Rice is the most important nutritional crop worldwide. The annual harvest/crop of rice is 570.6 million tons (status: 1999; source: FAS/USDA). It forms the staple nutrition for over 2.2 billion people in Third World countries. There will in all probability be a further one billion consumers of rice in twenty years' time. Worldwide there are 230 million children and adolescents who suffer from vitamin-A-deficiency disorders; such disorders result in complete blindness in one million of these children and in the death of a further million people each year. These people feed almost exclusively on rice. Polished rice grains (white rice) contains neither vitamin A nor provitamin A, the latter being converted into vitamin A in the body. 3.7 billion people suffer from iron-deficiency-related disorders (rice contains proteins that inhibit the uptake of iron in the intestinal tract). Various pests and diseases seriously affect the rice harvest:

• The yellow rice borer (Tryproryza incertulas) destroys 20 to 25 million tons of rice each year, an amount that could feed 100-125 million people.

• Fungi destroy 20 to 40 million tons of rice each year; this amount could feed 100-200 million people.

• The Tungro virus destroys 5 to 10 million tons of rice each year; this amount could feed 25-50 million people.

3. Cassava (manioc)

CCassava (also known as manioc) is cultivated in 92 countries worldwide. It provides thtthe staple nutrition for 500 million people in Africa, South America, and Southern InIIndia. The plant is capable of withstanding prolonged periods of drought, grows evoften on barren soils, can be cultivated and harvested at virtually any time of the
year, and can be easily propagated by taking cuttings.
It produces a large quantity of starch in its roots, which makes it attractive as a nunutritional crop. Harvested cassava roots are, however, very sensitive and start to decompose within the matter of only a few hours.
C Cassava plants form a substance that releases highly toxic cyanide. While tratraditional processing methods (grating, washing out, pressing, and roasting of cacassava flakes) can considerably reduce the cyanide content, these tasks are
Highly time-consuming and work-intensive. Also, almost 25% of the harvest yield is lo llost as a result of the mechanical processing. In many cases it is not always popossible to completely eliminate the cyanide, resulting in impairments of the flavour anand health risks. Cassava is also frequently eaten in its raw state - especially by yoyoung children - and this can naturally have life-endangering consequences.
YAA major part of the Cassava crop is also lost to pests and diseases.

Improving rice and cassava by genetic engineering

Genetic modification has been used successfully to develop rice varieties that are resistant to the yellow rice borer, and to fungal infection. Tungro virus-resistant rice varieties are currently undergoing trials. Efforts are also being made to enhance the content of iron in rice and to eliminate those substances that inhibit the uptake of iron in the intestinal tract.
Phosphate is one of the most important nutrients for plants and in many cases is the growth- limiting factor. Efforts are currently being made to enhance the capacity of the rice plant to take up phosphate. Another long-term objective is to incorporate the mechanism for nitrogen fixation in rice and other grain crops of most commercial relevance so that they no longer need be fertilized.
Long-term objectives of research efforts with cassava include effective pest and disease containment and also the prevention of the formation of cyanide and the rapid degradation process. Research along these lines is currently in progress.

4. Bioplastics made from plants

Bioplastics produced from genetically modified plants could help reduce the burden placed on the environment by conventional plastics. Much in the same way as animals use fat as an energy store, certain bacteria use substances similar to plastics. These can be isolated and processed into bioplastic. In contrast to plastics conventionally manufactured from mineral oil, bioplastics are produced from renewable resources such as vegetable fats, oils, or carbohydrates. They are completely biodegradable and can be used as a source of nutrients by a lot of naturally occuring microorganisms.
Bioplastic is still relatively expensive however, since the yield is very small. Genetically modified bacteria or plants may in future be used for industrial-scale production. Bioplastics could contribute in medicine; particularly in surgery where body-compatible implants are called for, or in the packaging-materials industry. The use of compostible shampoo bottles, beverage cartons, baby diapers, and other packaging materials could constitute an enormous reduction in the environmental burden imposed by conventional plastics.
Since May 1997, the British Cooperative Bank has been offering credit cards made of biodegradable plastic. The cards consist of "Biopol", a bioplastic manufactured by Monsanto using microorganisms. Biopol is obtained from renewable resources (e.g. sugar or vegetable fatty acids) and can be disposed of by composting, being 99.9% free of the ecologically problematic plastic PVC.
Employing genetic-modification methods Monsanto has also developed plants (oilseed rape) that produce relatively small amounts of Biopol (5% of the total weight) in their cells. The ultimate aim is to develop plants that consist of up to 20% by weight of Biopol, thereby enabling various bioplastics to be produced for a wide variety of applications.

5. Plants that degrade and are resistant towards deleterious substances

Genetic modification not only offers assistance in avoiding environmental damage - it can also be applied to relieve ecological damage that has already occurred, by using microorganisms or plants that degrade various pollutants.
The methods traditionally used to eliminate industrial pollution are limited: contaminated soils for example, are excavated and deposited at waste dumps or else incinerated in special facilities. In both cases the transport costs involved are high, and the humus - which is important for the fertility of the soil - is lost in the process. When the soils are deposited, the pollutants are not destroyed, they are merely removed from the public eye, and the threat is merely postponed. In built-up areas, it is often impossible or at least extremely difficult to remove contaminated materials.
Bio-remediation constitutes an efficient, ecologically compatible, and inexpensive alternative to traditional techniques. Ideally, these methods enable the pollutants to be degraded into inorganic compounds in situ in the soil or groundwater using naturally occurring microorganisms.
Aluminium-tolerant plants: Many soils worldwide are contaminated with aluminium, with the result that harvest yields are severely reduced. A Mexican research team has transferred the gene for an enzyme responsible for the development of citric acid to various plants, such as, papaya and tobacco. Compared with normal plants, these exhibit significantly better growth in aluminium-contaminated soils. While this should not detract from the importance of avoiding contamination of soils with aluminium in the first place, plants such as these could one day play a decisive role in solving problems where such contamination has already occurred.
In another development, American scientists at the University of Georgia have succeeded in cultivating mustard plants that have the ability to take up mercury and convert it into a chemical compound that is far less damaging to the environment. If the results of the laboratory experiments translate into practice, in future it might be possible to clean up mercury-contaminated soils by the cultivation of such plants instead of having to deposit these soils in special waste dumps.

6. Pharmaceutical drugs produced by plants

Plants can also be genetically modified such that they are capable of producing vaccines, pharmaceutical agents, or other therapeutically valuable proteins. No such products are on the market yet, but research efforts in this area are already well underway.
Human glucocerebrosidase (HCG) is used in the treatment of Gaucher patients (a congenital metabolic disorder). This is currently the most expensive pharmaceutical drug worldwide, costing about 160,000 US dollars per patient per year. The pharmaceutical agent is administered to the patient at one- to two-week intervals. The dose used corresponds to an equivalent of roughly 2,000 placentae from which the human protein is isolated. Since 1997, Genzyme who produce this drug, have been using genetically modified mammal cells as an alternative means of production. This has not yet resulted in a reduction in the price of the pharmaceutical product however. The corresponding gene has also been transferred to tobacco plants, achieving excellent results: one single tobacco plant produces the quantity required for an entire weekly dose. It therefore looks likely that it will be possible to produce the drug in greater quantities and more inexpensively in future.
Cholera vaccine from bananas: Efforts are currently being made to modify bananas such that they are capable of producing a vaccine against cholera. This vaccine would have the advantage of being ready-packed (in its skin), having a natural expiry date (the rotting of the banana), being easy to administer (eating the banana), and being able to be produced where it is required (in Third-World countries) in an environmentally sparing manner.

Other examples

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