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Thread: Genetic Modification

  1. #1
    Silver Member Graeme's Avatar
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    Genetic Modification

    It is reported that scientists at the International Rice Research Institute are pursuing an ambitious project which involves transforming the way in which rice photosynthesises. This will require some serious genetic restructuring.

    Most plants use an enzyme called rubisco to convert carbon dioxide into sugars containing three carbon atoms - a process known as C3 photosynthesis. But at temperatures above 25c, rubisco begins to bond with oxygen instead of carbon dioxide, reducing the efficiency of the reaction. As a result certain plants in warm climates have evolved a different mechanism, called C4 photosynthesis, in which other enzymes help to concentrate carbon dioxide around the rubisco and the initial result is a four-carbon sugar. In hot, sunny climes these C4 plants are half as efficient again as their C3 counterparts. They also use less water and nitrogen. The result, in the case of staple crops, is higher yields in tougher conditions.

    Turning a C3 plant into a C4 one is tricky since it involves wholesale changes in anatomy.

    The IRRI's crop scientists plan to screen the Institute's collection of 6 000 varieties of wild rice to see if any of them display a predisposition for C4 photosynthesis. Other researchers, meanwhile, are trying to isolate the genes responsible for C4 plants' unusual anatomy and biochemistry. A few years ago geneticists managed to get rice to produce some of the enzymes needed for C4 photosynthesis by transplanting the relevant gene from maize.

    The task is daunting and will take ten years or more, but the potential is enormous. Success would not only increase yields, but also would reduce the need for water and fertilisers, since C4 plants make more efficient use of both. Other important C3 crops, such as wheat, sweet potatoes and cassava, could also benefit. If it all works, a second and great green revolution beckons.

    (See Economist, 9-12-06)

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    Silver Member Graeme's Avatar
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    GM in South Africa

    Maize Streak Virus

    Maize is not native to Africa, and since its arrival from the Americas in the early 1500s, a virus found in local grasses has evolved a way to attack it. Plant breeders have tried for a quarter of a century to develop crops that are immune to the disease by crossing maize with partially resistant maize grasses. Unfortunately they have met with little success. The pattern by which resistance genes are inherited has proved elusive.

    Dr Jennifer Thompson and Dr Edward Rybicki of UCT have managed to insert a modified viral gene into the maize. This gene encodes a mutated version of one of the proteins that the virus needs to copy itself. When expressed at high levels in a plant infected with maize streak virus, the modified protein out-competes the normal version, throwing a spanner into the works of viral assembly. That has been demonstrated in greenhouses at least, by Panner Seeds, a seed supplier in Greytown, Natal, and the trait has successfully passed itself down four generations of crop. If further crosses do well, field trials will take place later this year.

    Those would be the first of such trials of a genetically modified crop in Africa, and if successful, this maize would be the first genetically modified crop created in a developing country - the first, it is to be hoped, of many.

    Remember, maize is not only an essential foodstuff; via ethanol, it is fuel too.

  3. #3
    Site Caretaker Dave A's Avatar
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    I've been reading some sources who are not quite so excited about the viability of maize to ethanol. For example, (from memory), to reduce USA's dependence on fossil fuel by 20% would take almost the entire USA maize crop. Not sure about the exact number, but it wasn't promising.

    However, the talk and chemical viability has certainly done wonders for the maize price!

    Anyway - Well done Pannar!
    Last edited by Dave A; 11-Feb-07 at 08:13 PM.
    The trouble with opportunity is it normally comes dressed up as work.

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