Europabio's Biotechnology Information Kit

An overview of agrifood biotech plants and applications

Introduction

The application of genetic modification pursues more or less the same objectives as has been the case with conventional breeding and cultivation methods, namely the production of high-yielding, robust plants that are resistant towards pests and diseases. In many cases however, genetic modification is capable of achieving these aims more efficiently. The cultivation of transgenic crops that possess tolerance towards herbicides or resistance towards certain pests has already been achieved (first-generation products). Research into aspects such as resistance towards threadworms (nematodes) and stress tolerances against drought or high salt concentrations have not progressed as far. Besides these plants with improved cultivation properties scientists are developing "second generation plants" that can provide better qualities of the processed products, i.e. healthier food with higher contents of vitamins or amino acids, starches that are suitable for certain industrial purposes etc.

1. Current research objectives worldwide

1.1. Product quality: enhancing the nutritional value

- More provitamin A in rice grains:

Husked rice contains neither vitamin A nor pro-vitamin A (the latter is converted into vitamin A in the human body). This is why people of tropical countries such as China, India, Burma, Malaysia or Indonesia, where nutrition consists virtually exclusively of rice, suffer from vitamin A-deficiency disorders. The World Health Organization estimates that some 230 million children and adolescents are affected by this disorder. Vitamin A deficiency weakens the body's resistance to pathogens - with fatal consequences for over one million people each year. It also results in roughly 350,000 pre-school-age children becoming partially or even completely blind every year. A long-term objective of research has been reached. Crop scientist Ingo Potrykus (Technical University - ETH - Zürich, Switzerland) has genetically engineered the production and storage of pro-vitamin A in grains of rice themselves, resulting in a pronounced improvement in nutritional value.

- Better composition of oil plants:

Oil yield, which in most oil plants amounts to 20% to 45% of the seed weight, can in the opinion of experts be increased to 60% to 70% by genetic modification. Methods used for the modification of oil composition - in particular with regard to the degree of saturation of oils - are already available. The DuPont company has genetically modified a soybean in such a way that it produces more oleic acid (over 80%) and fewer saturated fatty acids than a conventional soybean. The oil produced from such modified soybeans is better suited for human nutrition in terms of its composition and is also more thermostable than normal soy oil.

- More essential amino acids:

Humans are capable of synthesizing only ten of the twenty amino acids that we require as components of proteins. Others must be obtained as essential amino acids via nutrition; these include lysine and methionine. Higher plants are more versatile in this regard, and can synthesize all twenty amino acids themselves. Unfortunately the proportion of some amino acids in important basic food plants is very low. With the aid of genetic modification, attempts are being made to enhance the nutritional value of important crops such as maize, soybeans, and oilseed rape by increasing the content of essential amino acids. So far it has been possible to achieve a four-fold increase in the content of lysine. This is of great relevance particularly with regard to the coverage of protein requirements in developing countries, but it also improves the suitability of these plants as animal feed. Some 200,000 tons of lysine are currently manufactured by fermentation worldwide each year and added to animal feed as a supplement.

1.2.Product quality: delaying the ripening process

The natural ripening of fruits and vegetables is coupled with the production of ethylene, which specifically occurs in plants. Ethylene triggers a whole series of biochemical processes: on one hand the desired formation of aroma and taste properties and the production of valuable ingredients (e.g. vitamins, polysaccharides), on the other, however, degradation processes that are responsible for the "softening" of the fruits and vegetables. Ripe fruits and vegetables are too sensitive to be capable of surviving long transport routes without damage. For this reason, they are harvested "green", transported in a refrigerated state, and treated with ethylene at their destination in order to trigger or accelerate the final ripening process. With the aid of genetic modification it is possible to retard the degradation processes, which enables vegetables and fruits to be kept longer after their harvest. This has the advantage that they can be harvested in their ripe state and thus generally taste better, too.

- Sweet melons:

One object of research is a melon with a genetically retarded ripening process. In comparison with conventional melons, which as a rule do not possess the full sugar content when harvested early, the genetically modified melons can ripen on the plant and thus accumulate higher quantities of soluble saccharides. They can thereby attain a better taste than their conventional counterparts.

- Tomatoes with a delayed ripening process:

The FlavrSavr® tomato manufactured by the Calgene Company was the first genetically modified food licensed for human consumption; it was launched into the American marketplace in 1994. Genetic modification of the mechanism of cell wall degradation in the tomato resulted in the fruit keeping for a longer time. It can ripen on the stem and need not be picked in its green and unripe state. During the ripening process on the stem, it develops not only its colour, but also valuable taste properties and other ingredients (e.g. vitamins). The tomato does not soften after harvesting, which means the processor is given more flexibility with regard to transport and storage. Another company has also developed a tomato with retarded ripening properties. This tomato is particularly suited for the production of tomato pulp: in conventional tomatoes, the degradation of the cell walls must be prevented by heating to obtain a product with the desired viscosity. The heating process, however, results in the destruction of aromas, and is also energy-consuming. Since the degradation of the cell walls proceeds less rapidly in the transgenic tomato, the amount of energy required for the heating process is correspondingly lower. In the United States alone, the energy savings made possible amount to roughly 100 million US dollars.

1.3.Product quality: better taste

-Sweet but low in calories:

Thaumatin is a sweetener that is sweeter than sugar yet low in calories. It is produced by a plant, Thaumatococcus danielli, which is at home in Western Africa but difficult to grow elsewhere. Using genetic modification it has been possible to breed potatoes that produce thaumatin, resulting in a sweet-tasting potato variety. This might also be achieved in other plants. Such a natural, non-carbohydrate-containing sweetener could also be employed in dietetic products (e.g. for diabetics) or else to enhance the aromatic properties of fruit and vegetables. Thaumatin is produced in genetically modified microorganisms.

1.4. Product quality: Removal of undesirable properties

-Removal of allergens:

In the future it may be possible to de-activate or completely eliminate allergens using genetic modification. In Japan, rice triggers an allergic reaction in predisposed persons. Since rice is a staple food in Japan, this constitutes a major problem for the people concerned. Efforts are therefore being made to breed a hypo-allergenic rice variety that is no longer capable of triggering such an allergic reaction. Experiments are currently in progress at a number of laboratories; these have as yet yielded only partial success, since it has not been possible to completely eliminate the allergens responsible.

-Removal of proteins that inhibit digestion enzymes:

Many plant seeds contain so-called anti-nutritive proteins, which inhibit digestive enzymes. It is assumed that these proteins have evolved as a measure to deter herbivores. Rice, for example, contains proteins that block the uptake of iron in the intestinal tract. As a result, 3.7 billion people, in particular women, suffer from iron deficiency. Efforts are therefore underway to remove those proteins in rice that inhibit the uptake of iron in the intestine.

1.5. Agronomic properties: Insect resistance

Genetic modification conferring resistance towards insects has mainly been based on the incorporation into plants of Bt-toxin genes from the soil organism Bacillus thuringiensis. This range of Bt proteins has toxic effects on specific insect species. In maize, for example, it offers protection against the larva of the corn borer beetle, in potatoes against the Colorado potato beetle, and in cotton against the parasitic insect Heliothis virescens (commonly known as the tobacco budworm or in some regions cotton bollworm) and Heliothis zea (commonly known as cotton bollworm, corn earworm, tomato fruitworm). The highly specific effect of Bt proteins has been exploited in the agricultural sector to combat pests for some 40 years. Processed into biological spraying agents, the proteins are commonly used, for example, in vegetable-farming areas to fight cabbageworms. In connection with Bt maize it has been possible to increase harvest yields by as much as 7% in 1997 and to achieve a cost saving in the amount of 119 million US dollars. This cost saving results from decreased dependence on weather conditions affecting the timing and effectiveness of insecticide application because the Bt toxin remains active in the plant throughout the crop year. These improvements in pest control reduce pest losses and pesticide application leading to higher yields.

1.6. Agronomic properties: virus resistance

It has long been known that presence of a harmless virus attenuates the extent to which subsequent infections with related, strongly pathogenic viruses take effect in plants. This phenomenon, known as cross-resistance, is essentially based on the presence of virus-sheath protein and provides the opportunity for the use of genetic modification. In the laboratory, the gene that encodes the virus-sheath protein is isolated and stably incorporated into the genome of the plant in question, resulting in the production of the virus-sheath protein in very small quantities throughout the plant. This confers protection against virus disease. This procedure has already been employed in potatoes, pumpkins, papayas, and sugar beets.

1.7. Agronomic properties: fungus resistance

The approaches currently being considered to confer resistance to fungal infection are generally still at the basic-research stage. Two possible strategies are first, the constitutive formation of defence substances (in nature these defence substances are produced locally in the plant and only in reaction to an infection) and second, a modification of the vegetable host/pathogen-recognition system. In Switzerland, scientists have succeeded in breeding a rice grade that is far less susceptible to one of the most relevant damaging fungi. Fungal infections destroy 20 to 40 million tons of rice each year, and fungus-resistant rice varieties could ensure nutrition for 100-200 million people.

1.8. Agronomic properties: herbicide tolerance

Glyphosate-tolerant soybeans were genetically modified in such a way that they form an enyzme originating from a soil microorganism. This protein makes the soybean resistant towards the herbicide Roundup (active constituent: glyphosate), hence the name Roundup Ready® soybean.
The same principle and the associated advantages also apply to the glufosinate-tolerant oilseed rape. Using genetic modification, LibertyLink® oilseed rape has been made resistant to the herbicide Liberty (active constituent: glufosinate).

The herbicides glufosinate and glyphosate make it possible to combat weed growth after the germination of the plants and the weeds (in the so-called "post-germination phase") and in many cases can replace the use of pre-germination herbicides.
In addition to the economic benefits of glufosinate and glyphosate, there are also significant ecological arguments in favour of these herbicides. After their application they are rapidly degraded in the soil and do not accumulate (the half-life e.g. of glufosinate, depending on climatic conditions is 3-20 days). It has been shown that these herbicides do not enter groundwater except under extremely adverse conditions (e.g. very high groundwater levels). Even then, this does not result in any risk to the environment. All findings to date indicate that there is no enrichment of the herbicides or their transiently occurring metabolites in soil. The ultimate degradation products in the soil are naturally occurring substances such as phosphate, carbon dioxide, or water. The high degree of safety associated with the use of these herbicides has also been demonstrated by the many years of experience in ecologically sensitive systems since the beginning of the 1970s and the 1980s, respectively.

1.9. Agronomic properties: Nitrogen fixation

Nitrogen is one of the most important nutrients for plants. Some leguminous plants such as beans, peas, and lentils are able to "fix" nitrogen from the atmosphere by interaction with microorganisms. Most of our important crops, however, must take up nitrogen from the soil in the form of ammonium compounds or nitrate. Since the soil becomes depleted in this process fertilizers are generally applied to fields. A long-term objective of genetic modification is therefore to confer the property of nitrogen fixation on grain crops of most commercial relevance.

1.10. Agronomic properties: temperature resistance

The winter flounder, a species of fish, is capable of producing an enzyme that discourages formation of ice crystals. Using genetic modification, scientists have succeeded in introducing the gene responsible for this property into tobacco plants. This results in the inhibition of ice crystal formation in the plant cells. This modification may play an important role in particular with the cultivation of citrus fruits.

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