Popular

Article

Genetically Modified Crops: Problems and Prospects

M. A. Nishan College of Agriculture, Vellayani, Thiruvananthapuram, Kerala – 695522

Email: nshan.ma@gmail.com

Introduction Genetically Modified Organisms (GMO’s) are defined as those organisms that contain a gene (s) or genetic constructs of interest that has been artificially inserted by molecular or recombinant DNA techniques (genetic engineering) instead of the natural or conventional methods. The GMO, thus, carries ‘transgene(s) which when integrated and expressed stably and properly, confer a new trait to the organism, which was not present earlier or enhance an already existing trait. The term Genetically-modified foods or GM foods is most commonly used to refer to foods produced from transgenic plants or animals (Gupta, 2011)

Genetic Modification Genetic modification involves altering an organism's DNA. This can be done by altering an existing section of DNA, or by adding a new gene altogether. When a scientist genetically modifies a plant, they insert a foreign gene in the plant's own genes. The result is that the plant receives the characteristics held within the genetic code. Genetic modification of plants occurs in several stages: 1. An organism that has the desired characteristic is identified. 2. The specific gene that produces this characteristic is located and cut out of the plant’s DNA. 3. To get the gene into the cells of the plant being modified, the gene needs to be attached to a

carrier. A piece of bacterial DNA called a plasmid is joined to the gene to act as the carrier. 4. A type of switch, called a ‘promoter’, is also included with the combined gene and carrier.

This helps make sure the gene works properly when it is put into the plant being modified. Only a small number of cells in the plant being modified will actually take up the new gene.

Popular Kheti Volume -2, Issue-2 (April-June), 2014

Available online at www.popularkheti.info

© 2014 popularkheti.info ISSN: 2321-0001

Popular Kheti ISSN: 2321-0001 183

Humans have been genetically modifying crops since the advent of agriculture through crop hybridization and natural mutagenic principles. With the rapid advances in biotechnology, a number of genetically modified (GM) crops or transgenic crops carrying novel traits have been developed and released for commercial agriculture production. Controversy over genetically modified crops has been heating up as questions concerning genetically modified crops multiply. In this article some of the pros and cons of GM crops are discussed.

Popular

Article

To find out which ones have done so, the carrier package often also includes a marker gene to identify them.

5. The gene package is then inserted back into the bacterium, which is allowed to reproduce to create many copies of the gene package.

6. The gene packages are then transferred into the plant being modified. This is usually done in one of two ways:

The first method uses Agrobacterium tumefaciens to introduce the gene(s) of interest into the plant DNA. Agrobacterium has been successfully used to transform a wide variety of plant species. The second method involves a device called a ‘gene gun.’ The DNA to be introduced into the plant cells is coated onto tiny particles of gold or tungsten. These particles are then physically shot onto plant cells. Some of the DNA comes off and is incorporated into the DNA of the recipient cells of host plant. The tissue explants are later cultured on media containing hormones and antibiotics to select transformed shoots. This method is followed mostly in those crops lacking host specificity of Agrobacterium.

7. The plant tissue that has taken up the genes is then grown into full size GM plants. 8. The GM plants are checked extensively to make sure that the new genes are in them and

working, as they should. (Awaneesh,2010)

Advantages of GM Foods 1) Insect pest resistance: Most of insect–pests belonging to Lepidoptera (moths and butterflies), Diptera (flies) and Coleoptera (beetles and weevils) cause severe yield losses every year. Bacillus thuringiensis (Bt) is a naturally occurring bacterium which produces crystal proteins that are lethal to insect larvae. Tools of genetic engineering have facilitated introduction of genes encoding insecticidal proteins of Bt in cotton, corn and other crop plants, enabling them to produce its own pesticides against insects such as the bores. Growing GM foods such as Bt corn or cotton or other crops has helped reducing the application of chemical pesticides. Less dependency on conventional pesticides have benefited cotton growers with the use of Bt cotton in China and India. It may also help other developing countries where similar risks over excessive use of conventional pesticides exist. 2) Herbicide tolerance: It is not economical to remove weeds by physical means, so farmers often spray large quantities of herbicides to kill weeds in crops. The manual weeding is labour intensive, time-consuming and expensive process. GM crops made resistant to one very powerful herbicide could help prevent environmental damage by reducing the amount of herbicides needed. Crop plants genetically-engineered to be resistant to one very powerful herbicide could help prevent environmental damage by reducing the amount of herbicides needed. A farmer grows these crops which then only require one application of weed-killer instead of multiple applications, reducing production cost and limiting the dangers of agricultural waste run-off. 3) Disease resistance: There are many viruses, fungi and bacteria that cause plant diseases. Plant biologists are working to create plants with genetically-engineered resistance to these diseases. The viruses cause considerable losses and are difficult to control through chemicals. The coat protein gene has been successfully employed against viruses. The commercial cultivation

Nishan MA, 2014, Pop. Kheti, 2(2):183-187

Popular Kheti ISSN: 2321-0001 184

Popular

Article

transgenic including squash and papaya having virus resistance is in progress in many developed countries. Fungal diseases also cause huge losses but have been controlled by fungicides while conventional breeding approaches have not proved much effective in many instances. Expression of chitnases, glucanases and other related genes has shown enhanced resistance to many fungal diseases in past. Progress has also been made in developing trangenics for resistance against many bacterial and nematode diseases. 4) Cold tolerance: Unexpected frost can destroy sensitive seedlings. An antifreeze gene from cold water fish has been introduced into plants such as tobacco and potato. With this antifreeze gene, these plants are able to tolerate cold temperatures that normally would kill unmodified seedlings (Jumba, 2010) 5) Drought tolerance/salinity tolerance: With population pressure more productive land is being utilized for housing thereby leaving farmers to grow crops in rain fed or other unsuitable areas. Creating plants that withstand long periods of drought or high salt content in soil and groundwater will help people to grow crops in inhospitable areas. Indian scientists are working on the transfer of salinity tolerance genes from mangrove tree species to annual crops. BADH gene cloned from a highly salt tolerant mangrove species, Avicennia marina has been transferred in tobacco and Brassica and is expected to confer salinity tolerance. The work on other crops is also in progress. 6) Nutrition: Malnutrition is common in third world countries. Vitamin A deficiency causes millions of childhood deaths every year in world. It is also major cause of blindness in children in developing countries. In many parts of the world, most of people rely on a single crop such as rice for the main staple of their diet that needed to be made nutritionally rich. The two scientists Potrykus of the Swiss Federal Institute of Technology and Beyer of Germany inserted genes from a daffodil (Narcissus pseudonarcissus) and a bacterium (Erwina uvedovora) into rice plants to produced modified rice popularly referred to as “golden" rice. It contains an unusually high content of beta-carotene (which body converts into vitamin A) and that can meet a total Vitamin A requirement of an individual in a typical Asian Diet. Rice fortified with iron was also created through introduction of proteins from kidney beans (Phaseolus vulgaris). Scientist’s claim that golden rice can address nutrition security problems of people including vulnerable children, nursing and pregnant mothers in the world. Potato is another non-cereal staple food crop in many parts of the world. It has also been genetically modified using a seed albumin gene Ama 1 from Amaranthus hypochondriacus. The Ama 1 protein is non allergenic and also rich in all essential amino acids. GM potato has potential of overcoming problems of protein calorie malnutrition and mineral deficiencies. Cassava is a staple for about 250 million people in sub- Saharan Africa. It is susceptible to diseases, not nutritious with a short shelf life. GM cassava has now been engineered which is more nutritious with longer shelf life, disease resistance and lower cyanide levels. GM cassava could save millions of lives from starvation in sub-Saharan Africa in years to come. 7) Pharmaceuticals: Medicines and vaccines often are costly to produce and sometimes require special storage conditions not readily available in third world countries. Researchers are working

Popular Kheti ISSN: 2321-0001 185

Nishan MA, 2014, Pop. Kheti, 2(2):183-187

Popular

Article

to develop edible vaccines in tomatoes and potatoes. These vaccines will be much easier to ship, store and administer than traditional injectable vaccines. 8) Phytoremediation: Not all GM plants are grown as crops. Soil and groundwater pollution continues to be a problem in all parts of the world. Plants such as poplar trees have be genetically engineered to clean up heavy metal pollution from contaminated soil.

Some Examples of GM Crops Crop Properties of the genetically modified variety Modification Soybeans Resistant to glyphosate or glufosinate

herbicides Herbicide resistant gene taken from bacteria

Corn Resistant to glyphosate or glufosinate herbicides, Insect resistance - using Bt proteins some previously used as pesticides in organic crop production.

New genes added/transferred into plant genome.

Cotton (cotton seed oil)

Pest-resistant cotton Bt crystal protein gene added/transferred into plant genome

Hawaiian papaya

Variety is resistant to the papaya ringspot virus

New gene added/transferred into plant genome

Tomatoes Variety in which the production of the enzyme polygalacturonase (PG) is suppressed, retarding fruit softening after harvesting

A reverse copy (an antisense gene) of the gene responsible for the production of PG enzyme added into plant genome

Potatoes Amflora variety produces waxy potato starch composed almost exclusively of the amylopectin component of starch

The gene for granule bound starch synthase (GBSS) (the key enzyme for the synthesis of amylose) was switched off by inserting antisense copy of the GBSS gene

Rapeseed (Canola)

Resistance to herbicides(glyphosate or glufosinate), high laurate canola

New genes added/transferred into plant genome

Sugar cane

Resistance to certain pesticides, high sucrose cane

New genes added/transferred into plant genome

Sugar beet

Resistance to glyphosate, glufosinate herbicides New genes added/transferred into plant genome

Sweet corn

Produces its own bioinsecticide (Bt toxin) Gene from the bacterium Bacillus thuringiensis added to the plant.

Rice Genetically modified to contain high amounts of Vitamin A (beta-carotene)

"Golden rice" Three new genes implanted: two from daffodils and the third from a bacterium

Source: http://en.wikipedia.org/wiki/Genetically_modified_crops

Disadvantages of Genetically Modified Crops There are several risks of these crops (Ghosh, 2001). They are:

• GM crops are a threat to environment and biosafety.

• GM crops themselves may become weeds and wild population leading to ‘superweeds’.

Popular Kheti ISSN: 2321-0001 186

Nishan MA, 2014, Pop. Kheti, 2(2):183-187

Popular

Article

• They may lead to adverse allergic reactions to human beings.

• Antibiotic resistance gene in GMO’s may lead to development of resistance to the antibiotics used to treat human and animal diseases.

• It may disturb the ecosystem by eliminating the natural populations/biotic communities, by altering nutrient cycles due to introduction of certain microbes and plants.

• It may aggravate the genetic uniformity, vulnerability to diseases and narrow down the genetic diversity.

• Dependence of farmers on multinational companies for seeds.

Conclusion There are many ethical issues related to the growing and consumption of genetically engineered crops. They hold potential to greatly increase the nutritional value of food as well as the productivity of crops, while at the same time provide many safety as well as environmental concerns. These decisions need to be looked at by all of humanity since everyone is directly affected by the choices. GM foods are not necessarily bad, but permitting the expansion of GM crop planting and use in our food without proper knowledge as to the effects, both short-and long-term is at best unwise and at worst highly dangerous.

References Awaneesh. 2010. Genetically modified crops in India [Online]. Agropedia, IITK. Available at

http://iitk.agropedia.in/content/genetically-modified-crops-india Ghosh SK. 2001. GM crops: Rationally irresistible. Curr. Sci.81:655-660 Gupta RK. 2011. Food security, genetically modified crops and environment. Int. Proc. Chem.

Biol. Environ. Engng. 4:305-310 Jumba M. 2010. Genetically Modified Organisms: The Mystery Unraveled. Trafford Publishers,

North America 182p.

Popular Kheti ISSN: 2321-0001 187

Nishan MA, 2014, Pop. Kheti, 2(2):183-187