Although technically, all crops can be considered as “transgenic crops,” since genetic modification is inevitable through their long periods of domestication, selection and controlled breeding, the term is used to mean plants which have been genetically altered through artificial means in order to obtain a certain desirable characteristic, whether from the same species or from a completely unrelated species (What are Transgenic Plants, 2004).
In the primitive times, transfer of genes happen through pollination and only to plants of the same species. Later, artificial gene transfer from one plant species to another of the same species or to some related species became possible through different traditional methods invented by man. These methods however do not permit transfer of genes from unrelated species. For example, a gene of a certain bean may benefit rice’s protein content but using the traditional methods of gene transfer, such is not possible.
It is the many discoveries in biotechnology, specifically, the development of recombinant DNA techniques which made possible the current definition of “transgenic plants. ” Biotechnology allows for the identification of genes related to a specific desirable characteristic and then their isolation for production from one organism to another. The other organism will then gain the benefits of the new characteristic.
This increases the potential for new and better varieties of plants with better combination of genes which are limited if traditional methods are used (What are Transgenic Plants, 2004). With the current definition of “transgenic plants,” the transfer of desirable genes is not anymore limited to plants of the same or related species, but may also come from another plant species and even from animals, microorganisms and artificially synthesized genes.
In addition, unlike the traditional methods of gene transfer, the current methods of producing transgenic plants do not require many generations of breeding to produce the desired individual. This is because biotechnological methods are more direct and specific in gene transfer. Meaning, the resultant individual may already possess the desired trait and without any contamination from genes that may be transferred unnecessarily if the traditional methods are used.
The new discoveries in molecular biology also make possible the creation of new gene constructs which could be used to produce better breeds. This is impossible in the traditional way of gene transfers (Villano, n. d. ) The most common application of transgenic crops today involves the enhancement of characteristics related to their environmental tolerance. Among these include improved herbicide tolerance, disease resistance and insect resistance (Villano, n. d. ). A. Herbicide Tolerance
Herbicides have been a common tool necessary in agriculture both in preventing the destruction by weeds and in increasing the crop yield. But despite these functions, the use herbicides per se could be harmful to the plants since residues of herbicides could remain in the soil for a year or more and eventually become toxic to the crops (Transgenic Crops Currently on the Market, 2004). Herbicide ingredients such as glycophosphate, for example could disrupt the plant’s biosynthetic functions that could result in their ultimate deaths and thus, decreased crop yield.
Genetic Engineering of plants answers this problem by modifying them to become tolerant or resistant to specific harmful ingredients of herbicides. Tolerance or resistance to the herbicides’ active ingredients is done by enabling the plants to produce specific enzymes that could counteract the effect of the active ingredients; immunizing the plants to the herbicide by altering the properties of the target substances of the herbicides’ ingredients; and by deliberate production of barriers to the uptake of herbicidal ingredients.
Beets, corn, cotton, lettuce, poplar, potato, rapeseed, soybean, tobacco, tomato and wheat are some examples of plants that have been tested and developed for herbicide tolerance (Villano, n. d. ). B. Insect resistance The use of pesticides by farmers is necessary to thwart crop destruction by pests. However, most pesticides contain chemicals which by themselves are toxic to the crops. The developments in biotechnology make possible the removal of the use of pesticides as a process in growing crops, without risking the destruction of crops by the insects.
Through plant genetic engineering, plants could now be structured to produce natural toxins that could kill pests. Usually, this is done by incorporating genes of microbes known to produce natural endotoxins. One example of this microbe is Bacillus thuringiensis, which is usually found in the soil. When the gene from this microbe is transferred to a plant, the endotoxins, also called Bt from “Bacillus thuringiensis,” it becomes capable of producing the toxin which when ingested by the pest, could result in ion imbalance, paralysis and later, death (Transgenic Crops Currently on the Market, 2004).
The plants that are genetically engineered to produce Bt toxins are called Bt plant. Common Bt plants today are corn, to prevent infestations by rootworms; potatoes, against Colorado potato beetle; cotton, to prevent infestation by cotton bollworm, potato, against (Transgenic Crops Currently on the Market, 2004; Villano, n. d. ). Corn could also be genetically altered to receive genes from wheat to reduce insect damage while rice could receive a gene from bacteria for the same purpose (Transgenic Crops, 2000).