USING BIOTECHNOLOGY IN CROP DEVELOPMENT
Farmers have been practising a crude form of biotechnology for centuries by cross-breeding plants to introduce and maintain desirable characteristics. More recently, plant technologists have bombarded plant cells or small plants with radiation that damages DNA, causing random changes that so result in 'better' plants. However, the newest, truly biotechnological techniques involve genetic engineering and produce the genetically modified (GM) plants and crops that are so often in the news.
So, how are plants genetically modified?
Genetic modification (GM) usually involves the transfer of a single gene, together with an obvious marker so that the plant breeder knows which plants have taken up the gene. The gene chosen usually codes for a protein that gives plant a higher rate of growth, or makes it resistant to drought, pests or weedkillers, or that makes part of the plant more useful for the food industry.
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GM is done by first incorporating a gene into a plasmid (a small circular piece of DNA) and is then introduced into cells of the plant that is being modified. Sometimes bacteria can infect a whole plant; other techniques introduce the bacteria carrying the plasmid into individual plant cells. These are then cultured to produce plant tissue and then the whole plants that carry the 'foreign' gene.
A diagram illustrating the differences between conventional plant breeding, transgenic plant breeding and cisgenic plant breeding. Genetically modified plants could also be called transgenic plants, but this term tends to be used more commonly for animals that have been bred to carry specific genes. I'll cite two examples on transgenic plants using the Golden rice of Southeast Asia and the genetically modified cotton of India.
The Golden Rice of Southeast Asia
Rice is a staple food for over 3 billion people in Southeast Asia and Africa. Many people there have very little else to eat Golden Rice grain compared to white rice grain International Rice Research Institute (IRRI) •
Although rice is a good source of carbohydrate and protein, it does not contain very many of the essential vitamins and minerals that are needed to stay healthy. Those that are present are not easily taken up by the body during digestion of the rice.
Many people in the developing world therefore suffer iron, zinc and vitamin A, C and E deficiency symptoms. These make people less able to work, and cause reduced mental capacity, stunted physical growth and blindness. Because the deficiencies are particularly severe in pregnant women, there is an increased chance that babies and young children die.
Providing supplements to large parts of the population of Southeast Asia is theoretically possible, but it costs a lot, so is not really an option. General moves to extend the diet are difficult because of poverty. One answer is genetic modification of the rice to produce more of the required vitamins and minerals, and this has now become a reality.
Golden rice is now widely grown and is a good example of biofortification. The rice plants normally cultivated have been genetically modified to produce ß-carotene in rice endosperm. ß-carotene is converted in the body to vitamin A.
The rice plants were given two new genes that express the proteins phytoene synthase and carotene desaturase, both of which allow the plant to make β-carotene and concentrate it in the endosperm. The first generation of GM plants produced in 2002 was able to make a small amount of β-carotene. Later generations were improved so that the rice plants can now make higher β-carotene levels.
The GM plants produce rice that is high in β-carotene and which looks golden because of this pigmented molecule in its endosperm. It looks attractive, so people enjoy eating it-if it had turned out bright blue, there could have been a problem.
Some studies have already shown that growing golden rice does help reduce vitamin deficiencies in the local people. In the future, the plants may be modified again to enrich them with other vitamins and minerals. Over-expression of ferritin, an iron storage protein, has already been achieved in rice grains and the zinc levels in barley grains have been doubled by over-expressing a zinc-binding protein in the barley plant. Eventually, food scientists think it will be possible to combine all these genetic modifications into one rice plant, which would then provide all the necessary vitamins and minerals missing from the diet.
Secondly, let's discuss the effect of genetically modified cotton growing in India.
The Genetically Modified Cotton growing in India
India is a major exporter of cotton and the cotton crop is important to the Indian economy.
The cotton plant is easy to grow in hot climates but it can be severely damaged by insect pests - bollworm, aphids, jassids and whiteflies. These not only harm the plants directly, they also introduce plant viruses leading to disease.
Within the past decade, a genetically modified cotton plant which has a gene from the bacterium Bacillus thuringiensis, has been developed. The Bt gene produces a protein that is toxic to bollworms, so is resistant to attack by this pest. The first commercial cultivation was allowed in 2002. There was quite a lot of controversy over the results of the trials in the next two years, but a general conclusion emerged that the Bt cotton does have advantages over wild varieties.
Since then, more farmers in India have chosen to grow Bt cotton; 5 million acres were planted in 2005 and this went up to 8.1 million acres in 2006.
An Indian farmer, Eknath Shivram Pandit has grown corn and cotton for nearly 15 years and recently switched to Bt cotton. He has noticed many benefits on his farm and for his family. The cotton crop now suffers fewer insect infestations and so he needs to spray with insecticides only two or three times instead of 15 to 20 times. The cotton crops he has produced have also had higher yields, and the family's standard of living has improved
Pandit says: 'This technology is going to be very helpful. There has been a lot of benefit. This product has brought in money. With money, there can be education. I will buy more land for farming. Dig more wells. I can build a house. Save some money for my daughter's wedding and son's education'.
Since introducing Bt cotton to his farm, Pandit has been able to replace his ox cart with a tractor, which speeds up his visits to and from the local market. 'I am more enthusiastic about farming. It's worth it now,' he says. Wild type peanut (top) and transgenic peanut with Bacillus thuringiensis gene added (bottom) exposed to cornstalk borer larva.
THE EXPANDING USE OF GM CROPS
The use of GM crops has been expanding steadily over the past 10 years. In 2006, 10.3 million farmers in 22 countries across the world planted a total of 252 million acres of land with them. Over half of all GM crops were grown in the USA, with a further 30 per cent in South America. Canada and South Africa grew some GM varieties.
Indian and Chinese farmers represent about 7 per cent of the total. These farmers are the most enthusiastic farmers as GM crops in the developing world can mean the difference between making a good living, and starving. The greatest increase in GM crops is expected to be in developing countries during the next decade.
SOME ADVANTAGES OF GM CROPS
There is a lot of controversy about GM crops. Like all things, they have some advantages and some problems.
The advantages include: • a better tasting crop product, perhaps, with more nutrients; • crops that take less time to become mature and ripen, or crops that stay fresh longer once they are harvested; • crops that produce higher yield and are better able to withstand stress, such as cold or hot weather; • plants that have better resistance to disease, pests and herbicides.
Overall people in favour of GM crops argue that they allow more land to be used effectively, they make farmers in developing countries more self sufficient, they result in cheaper food and they can reduce the use of pesticides.
SOME PROBLEMS WITH GM CROPS
The major problem that is preventing more widespread use of genetic modified crops and foods is public suspicion and hostility. Opponents of GM foods are particularly vocal in the UK. In other countries in Europe, and in the USA people have accepted them more readily.
Here are some of the arguments made by people opposed to GM foods. • GM foods are bad for your health: swapping genes from one organism to another is unnatural, and therefore dangerous. What might be the effect of eating 'foreign' genes from bacteria? • Genes from GM plants might escape and get into other plants, creating 'superweeds'. Bacteria might pick up the plasmids that have been used to carry genes into plant cells, and then infect other plants. • The genes may spread outside crop plants, making weeds resistant to all known weedkillers. • GM plants might breed with traditional varieties, producing hybrids that are no use. Organic farmers might find that crops that have taken years to establish become contaminated with genes from GM crops. • Growing GM foods resistant to weedkillers and pesticides may affect insects and other useful wildlife which may then be lost. • The technology behind GM crops is only available to the multinational, large agro businesses, not the small, independent farmer. Organic farmers may find their products outsold by GM foods, which can be produced at a much lower cost.
EXAMPLES OF GM FOODS AND CROPS
The major GM crops grown today are herbicides and insect-resistant soybean, corn, cotton, canola and alfalfa.
Others include: • A sweet potato resistant to a virus capable of destroying most of the African harvest.
Golden rice - rice with increased iron and vitamins grown in Asian countries. • Plants able to survive in extreme conditions, such as tomato that can grow well in salty water.
Disease-resistant sweet potatoes
The sweet potato is an important crop in Africa. It is grown as a staple food source by the women and children of poor families, who harvest tubers daily meals. Larger harvests are done occasionally to trade for other products.
The sweet potatoes are very prone to a viral disease called Sweet Potato Virus Disease (SPVD). This is caused by the sweet potato feathery mottle virus and a strain of the sweet potato chlorotic stunt virus. Affected plants produce only tiny tubers. Some naturally resistant varieties do exist, but these produce low yields compared to the wild type plant.
Genetically modified sweet potato varieties have been developed that also give good yields of tubers and trials have proved successful. Farmers in Africa, from Uganda to Tanzania, have adopted these new varieties and the production of sweet potatoes has increased.
Salt-loving tomatoes
Millions of hectares of land all over the world become impossible to farm every year because irrigation techniques cause an increase in the salt content of the water and soil. Plants generally dislike salty conditions; a few specialised species can survive but most crop plants cannot.
In the past few years, agricultural scientists have developed a type of tomato that thrives in salty conditions. This makes it more likely that other plants can also be modified to become salt tolerant. The tomatoes take up the salt through their roots, but they then isolate it so that only ordinary water passes to the rest of the plant - the tomatoes themselves are not salty
The GM tomatoes can grow in water that contains 50 times more salt than freshwater. Seawater is 150 times more salty than freshwater, but researchers hope that further modifications may produce plants capable of living in seawater in the future.
Conclusion
All over the world, farmers have been using a traditional method of biotechnology like cross breeding of plants to produce some great results. But presently, biotechnology has taken another level which involves the use of genetic engineering to produce genetically modified (GM) plants. These set of crops are so modified that they exhibit higher growth rate, resistant to drought and are more beneficial to food industry.
Major examples of GM crops are the Golden rice of Southeast Asia and the genetically modified cotton of India. GM crops are known for tasting better, and the ability to resist disease and withstand stress. But, just like we know that all good things have its downsides. The major problem facing the widespread use of GM crops is public misgiving, resentment, and animosity. Some people argue that GM crops are harmful to the body, while some say only the rich can afford to use the technology thereby making it unaffordable for small farmers.
Finally, I'd say biotechnology has a huge lot of effects and benefits on crop production and development, irregardless of people's suspicious and hostility.
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