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The below mentioned article provides notes on genetic engineering of crops.
Genetic engineering of crops became available in the early 1980’s as genetic engineering techniques were being perfected. The advantage of genetic engineering is that it allows the transfer of a single gene, or a couple of genes, in a much more precise, controllable and predictable way than is achievable with conventional breeding.
Conventional breeding involves random mixing of the tens of thousands of genes present in a plant with the ten of thousands of genes present in another plant. In contrast, genetic engineering is a much more precise way of improving crops. Improvements can be achieved in much shorter time frames.
In the past, it took 10 to 15 years to introduce a new variety of sweet corn. This time has been cut in half using the tools of genetic engineering. In addition, genetically engineered crops are required to undergo extensive food and environmental safety assessment, whereas conventionally modified crops are not.
Today, over 800 million people face daily hunger; furthermore, a majority of the global population growth in the next 50 years will be in developing countries where malnutrition is already prevalent. Forty per cent of the world’s land use for agriculture is already seriously degraded.
In order to meet the nutritional needs of this growing population, cereal production alone will need to increase by 40% in the next 20 years. We simply cannot achieve the kinds of yield increases in a sustainable way using traditional methods of breeding.
Biotechnology is an important tool in addition to all of the other tools to produce a food supply that will be sustainable in the long run and will be able to meet these needs in the future.
Almost all of the world’s major crops are now being improved using genetic engineering, although initial efforts have focused on commodity crops-primarily corn, soybeans, cotton, canola and potatoes. However, there are many other crops, including other cereal grains and a number of vegetables and fruits that have been improved using genetic engineering and are in the commercialization pipeline (Table 1).
Biotechnology crops are the most rapidly adopted technology in the history of U.S. agriculture. The first genetically modified crops were commercially grown in 1996. USD A estimates for 2001 indicate that about 25 million acres (20% of global total) of corn, 82 million acres of soybeans (63%), 7 million acres of cotton (13%) and 3 million acres of canola (5%) grown globally are genetically modified varieties.
FDA has approved 51 different products that are in various stages of commercialization. One of the first products of plant biotechnology was insect resistant corn. A single gene encoding an insecticidal protein from Bacillus thuringiensis (Bt) was transferred into corn.
The Bt gene confers resistance to the European corn borer, a devastating insect pest. In addition to the European corn borer, corn earworm is another problem in sweet corn, and both need to be controlled.
Consumers typically throw away ears of sweet corn if they find worms, even though the heavy use of pesticides assures that the worms do not survive more than about an inch down the cob. Consumers who find worms in their frozen or canned corn are sure to register complaints with the company.
To avoid these problems, growers, particularly in the southern states that grow two or three crops of corn each year, may spray sweet corn up to 60 times in a season to control these pests. Adoption of this technology would result in a higher quality product and significant reduction in the use of pesticides.
Although the European corn borer and corn earworm have the word “corn” in their names, they affect many other vegetables, such as green beans and peppers. The same Bt gene in field corn can be transferred into other vegetables and confer resistance to those same, or related, insect pests.
The Bt gene has been transferred into potatoes to confer resistance to the Colorado potato beetle, a devastating pest in potatoes. The leaves of conventional potato plants are almost totally denuded by the Colorado potato beetle, and this lowers crop yields. The Bt gene also has been transferred into cotton.
The cotton boll in genetically modified cotton is protected from the cotton boll weevil; thus, yields are significantly higher. Cotton and potato crops receive extensive pesticide treatment in the United States, and use of the genetically modified varieties results in a reduction in pesticides.
The second major area of genetic modification is herbicide tolerance. Herbicide tolerant crops are tolerant to the more environmentally friendly herbicides, for example, glyphosate. Glyphosate and other broad- spectrum herbicides eliminate a variety of weeds, so the farmer can use one product instead of several different chemicals.
These products also significantly reduce crop injury, and, because they degrade quickly in the soil, farmers can be less concerned about crop rotation. One of the most valuable aspects of these products from an environmental perspective is that they encourage “no till” farming methods, which significantly reduce soil erosion.
The vegetable processing industry would value the same herbicide tolerance in sweet peas. Weeds growing in pea fields are harvested along with the peas. Pea fields are frequently contaminated with “nightshade,” a weed that has a berry the same size, colour and density as peas.
When these berries are thermally processed along with the peas, the berries harden and are highly unacceptable to consumers. Farmers have a hard time eliminating nightshade from their pea fields; herbicide tolerant sweet peas would simplify weed control and improve final product quality.
Farmers have recognized the benefits of crop biotechnology and have readily adopted it. Use of these crops has resulted in environmental and food safety benefits, including a significant 2.7 million pounds per year reduction in the use of pesticides, and modelling studies indicate that ground water contamination by herbicides can be significantly reduced when glyphosate tolerant crops are planted.
An additional benefit of Bt corn is that, because the worms cannot form holes in the corn, fungi that can produce toxic mycotoxins, e.g., fumonisin, cannot attack the corn, resulting in a cleaner, safer product.