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Genetic Diversity: The Foundation of Food
Why is genetic diversity important?
Over time people have used thousands of different plants for food. Today we rely on less than 20 plants for more than 90% of our calories (Figure 1.) Since so few plants provide so much of our food, we need these crops to resist pests and diseases, and to adapt to changing environmental conditions. This genetic diversity might contain a number of important traits. For example, one variety of corn may be resistant to a harmful fungus, another may have the ability to grow with little water and a third may be especially good for making corn chips. The greater the diversity, the greater the range of traits that can be combined to make new varieties. Only by preserving the diversity of crops can we preserve the genes that give them resistance.
The corn crop in the United States has very little diversity. Most farmers grow corn as a monoculture crop —every plant has a similar genetic make-up. In this situation diseases can spread dangerously fast and wipe out an entire crop. This is exactly what happened in 1970, when the southern corn leaf blight swept through the southern states of the USA and devastated the corn crop. Half of the crop of some southern states was lost, 15% across the country. The problem was that the corn in the US was uniformly susceptible to this disease.
One way farmers protect their crops is to use genetically different varieties of corn. There are two main options: 1) create genetically different plants through traditional breeding, and 2) use plants created by genetic engineering technology.
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 Traditional Plant Breeding: The first and traditional method involves combining the egg and sperm (contained in the ovule and pollen, respectively) of two distinct corn plants. Mating ‘parent’ plants passes along traits to offspring plants. Plant breeders look for ‘parent’ plants in areas with high genetic diversity: habitats with wild corn relatives, and small-scale farms. These cultivated varieties (known as landraces) have special characteristics based on where they grow. |
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Genetic Engineering: This process involves introducing DNA into an organism by means other than by combining a sperm and egg. Essentially, scientists “cut and paste” DNA from one organism into another with the aid of bacteria or a technology called gene guns. This makes it possible to add DNA from one organism into an unrelated organism, for example, the brazil nut and soy bean.
Scientists, farmers, environmentalists and consumers debate the benefits and concerns of genetic engineering. Those who support this technology argue that it is faster than traditional plant breeding and can improve plants in ways traditional breeding cannot. Opposing parties raise many concerns because there is insufficient research on the effects of genetically modified organisms (GMOs) on the environment or public health. You can find many resources on the web to learn more about genetic engineering and the surrounding debate.
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continue to environment: how we are protecting the genetic diversity >>
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