Applications of biotechnology in agriculture
Applications of biotechnology in agriculture
The application of biotechnology in agriculture could allow an increase in production without the need for massive use of land, labor and capital, as well as decrease or abolish the use of chemical fertilizers, herbicides and pesticides that have so damaged the environment to date. Among the most common methods to introduce into plant cells genes from other organisms or artificially synthesized is the use of the bacterium Agrobacterium Tumefaciens, which normally carries a plasmid containing a gene capable of inducing tumors in plants: this gene is replaced with the one carrying the desired character, the plasmid is then reinserted into the bacterium that infects the plant cell and transfers the DNA. An alternative to this method is to “shoot” DNA fragments wrapped in tiny metal capsules directly into the plant cells. In both cases the plant cell incorporates the DNA into its genome, and then generates whole plants, carrying the new gene and therefore the new character.
The main characteristics that can be acquired by plants through the insertion of a foreign gene and interesting from a commercial point of view are resistance to pathogens, resistance to herbicides and resistance to environmental stress. Resistance to viruses and bacteria, which can make the plant sick or even die, and which cause considerable losses to agriculture, is an extremely important characteristic. In fact, the traditional methods of prevention and treatment, such as crop rotation and the use of chemicals able to limit the infection by these pathogens, have been only partially effective and, sometimes, harmful for the environment.
The first genetically modified plants able to resist viral infections were obtained around 1986, thanks to the insertion of the gene responsible for the synthesis of the protein that forms the viral envelope itself: the plants equipped with this protein, in fact, showed resistance to the virus wrapped in that same protein. This means, clearly, that resistance cannot be conferred against any type of virus, but towards a specific virus, possibly the most specific and harmful for each particular type of plant. Genetic engineering has also succeeded in conferring insect resistance to some plant organisms using a particular gene taken from the bacterium Bacillus thuringiensis. This bacterium was already used as a biological insecticide, because it is able to inhibit the functionality of the digestive system of insects, and therefore to poison them. Its capacity is given by the presence of a gene that encodes for a toxin: to insert this gene in the vegetable chromosomes means to give directly to the plant the possibility to kill its own parasites. Moreover, it has been demonstrated that this toxin is not harmful either for the plant that produces it or for those who feed on it, as it acts only against some proteins typical of insects.
Thanks to these techniques it has been possible to generate maize resistant to the corn borer, a voracious butterfly that, at the larva stage, devours the stem of the plant. The modified maize has been subjected to careful analysis before being put on the market and Italy, despite having authorized its importation at the beginning of 1997, has allowed its cultivation only afterwards. Also climatic conditions have a fundamental importance both on the quantity and on the quality of agricultural products, and scientific interest has been focused on the biochemical and genetic basis of the response of plants to environmental stresses such as cold, drought or salinity variation. It was thus highlighted that there are systems common to many types of plants related to the expression of a few genes.
In March 1999, a group of Japanese researchers demonstrated that by suppressing the activity of a single gene that is normally activated in response to environmental stress, it was possible to make a transgenic Arabidopsis plant resist cold. This organism shows a growth and production fully comparable to that of unmodified plants, but has the ability to resist without water for two weeks, at high salt concentrations and temperatures below 0 ° C for two days. The presence of some genes that actively confer resistance to environmental stresses has been highlighted, and experiments of genetic transformation have made possible the birth and development of plants that, having acquired these genes, are able to respond by protecting themselves from adverse conditions; research in this field are now directed towards plants of agricultural interest.
Weeds are a serious problem for crops: their presence can take away water, nutrients and light from the cultivated plants, sometimes strongly reducing their production; moreover, in order to be separated during the harvest, weeds require a greater work and economic commitment. Until now, weeds have been combated with herbicides: each herbicide used had to be directed specifically against a particular weed, so as not to damage the cultivated plant; the presence of multiple weeds in the same crop, therefore, required the use of multiple herbicides, with significant economic and environmental consequences.
Genetic engineering has made it possible to confer resistance to herbicides to the plants of interest through two alternative mechanisms: either they become able to inactivate these substances, or they present a modified form of the enzyme targeted by herbicides, becoming insensitive to them. It is therefore possible to use less specific herbicides with a greater range of action in order to obtain a pest control action that is completely effective and harmless to the crop. An example of this technique is given by the soybean made genetically resistant to glyphosate, the active ingredient of many herbicides that is able to inhibit an enzyme vital for all plants. The genetically modified soybean contains a bacterial gene that confers resistance to this herbicide, and was carefully analyzed before being placed on the market, to ensure that the desired change did not generate other, unexpected changes; that the genetic change was stable, that is, heritable, and that the gene introduced could not be transferred from one individual to another according to unforeseen mechanisms.
Detailed molecular analyses have shown that the genetic modification does not generate further changes, especially with regard to the synthesis of new allergens, which is stable through several generations and is not transferred to other organisms. Moreover, the substance produced has characteristics that make it extremely attractive: it is harmless to animals and rapidly decomposes into non-polluting residues.
Great efforts of genetic engineering are also directed towards the improvement of the nutritional properties of plants and to obtain the production of substances of industrial interest. One of the most studied and discussed results has been that of the Flavr Savr tomato that, thanks to the presence of a non-functioning gene, rots in a much slower time than the natural tomato. This allows the maintenance of the product for a long time, also facilitating its distribution.
As it was experimentally necessary to insert, together with the non-functioning gene, a gene responsible for the resistance to a particular antibiotic, this product did not obtain a great consensus: in fact it was feared that the resistance to the antibiotic could be passed from tomato to some bacteria, or even to the consumer, with evident harmful consequences. Later on, this fear has been removed, as it has been demonstrated that the gene for antibiotic resistance undergoes a rapid degradation.
Other results of biotechnology applied to agriculture have led to the production of seedless grapes, strawberries resistant to cold, melons able to use sea water to survive, potatoes that do not absorb frying oil. An interesting application has the aim to accumulate in the leaves of legumes, rich in essential components of food and used in all countries, the important proteins that normally are deposited only in the seeds. Biotechnologies applied to agriculture represent a considerable source of income, and therefore they have attracted the attention of many private companies that base their activity on the development of these researches.
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