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Agriculture: Recombinant DNA

Biology (Year 12) - Biotechnology: Applications

Ben Whitten

Recombinant DNA technology is defined as the tools and techniques which are used to transfer a gene from a cell of a member of one species to the genome of a different species, and has been found to have many applications in agriculture;

  • Producing crops with faster growth rates

  • Higher yield

  • Disease resistance

  • Herbicide resistance

  • Tolerance to climate change

Transgenic organisms (who are also referred to as genetically modified organisms, or GMO's) have been specifically engineered in order to produce desirable traits. Bioengineering is the combination of both biological tools and engineering tools in order to create a usable product, for example, a transgenic organism.

The use of Agrobacterium in agriculture

The soil bacterium Agrobacterium tumefaciens has been widely used in agriculture, as it has evolved the ability to penetrate cell walls with its plasmid and insert specific genes into the genome of the host cells. The Ti plasmid in A. tumefaciens causes an infectious disease in plants known as crown gall disease, and despite this, scientists have gained the ability to control and make use of this phenomenon in order to produce GMO's which are desirable to humans. A gene is cut from a foreign source, inserted into the Ti plasmid to make a recombinant plasmid, and returned to A. tumefaciens for cloning. The bacterial vector can then be cultured with plant cells that are susceptible to penetration by the plasmid, and following penetration of a host cell, the genes are inserted, transforming the host plant into a genetically modified plant.

Transgenic organisms engineered for resistance

Herbicide Resistance

  • A herbicide is a substance used to control weeds, ideally leaving a crop unharmed, however spraying herbicides on crops to kill the weeds will usually damage the crop itself

  • Herbicide-tolerant crops have been produced to combat this, a notable one being the glyphosate-resistant Roundup Ready© soybeans have a gene inserted into them from a bacterium; Roundup Ready crops are resistant to the herbicide of the same name, which contains glyphosate - a chemical which inhibits a biochemical pathway in plants, preventing them from producing essential amino acids and causing them to die

Disease resistance

  • The bacterium Bacillus thuringiensis has been successfully introduced into cotton plants through recombinant DNA technology via CSIRO

  • The Bt cotton produced is a natural pesticide to the Helicoverpa caterpillar, which is known to damage crops in Asia, Europe, Africa and Australia

Faster growth rate

  • The AquAdvantage salmon© has been engineered using recombinant DNA technology, and has the capability of growing at double the rate of conventional Atlantic salmon

  • The GM fish grow to market size in a mere 16-18 months, as compared to the previous time frame of 3 years

Greater product quality and yield Increase in quality (nutrition) in rice

  • The WHO (World Health Organisation) has estimated that approximately 120 million people suffer from a vitamin A deficiency, and one to two million die of it each year

  • To combat this, Golden rice has been engineered, a type of rice that has a high amount of beta-carotene in it (a precursor of vitamin A), and is what gives the crop its bright yellow-orange colour

  • Golden rice is manufactured using Agrobacterium

Pest and herbicide resistance

Organisms can be genetically engineered to resist the actions of pests and herbicides. Pest resistance refers to how some crops are resistant to pests/insects when confronted with a pest invasion, resulting in a more desirable crop yield. Herbicide resistance is the inherited ability of an individual plant to survive a herbicide application that would kill a normal population of the same species. Herbicide resistance does not equate to poor performance of a herbicide. Resistant weeds can often survive application of herbicide at rates that are much greater than the recommended rate.

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