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Overview
Commercial
cultivation of transgenic crops
Figure
2.1 Commercially cultivated genetically modified crops 2002
Emerging
scientific discoveries for addressing complex traits
Table
2.1. Complex traits
being addressed through emerging science
Note:
For references cited within this chapter, direct links are provided
to the appropriate section of the Annotated Bibliography
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Applications
of modern genetics are being used to improve the efficiency and sustainability
of agricultural practices today. For example, recent discoveries have
led to:
· Better
understanding of how plants function, and how they respond to the environment.
· More
targetted selection objectives in breeding programs to improve the performance
and productivity of crops, trees, livestock and fish, and post harvest
quality of food.
· Use
of molecular markers for smarter breeding, by enabling early generation
selection for key traits, thus reducing the need for extensive field
selection.
· Molecular
tools for the characterization, conservation and use of genetic resources
· New
molecular diagnostics, to assist in the improved diagnosis and management
of parasites, pests and pathogens
· New
vaccines to protect livestock and fish against lethal diseases.
Such
applications, which are already making substantial contributions to
agriculture in both industrial and developing countries, use information
derived from modern genetics and new molecular techniques. (For examples,
see: CGIAR 2000a; IFPRI
2001; ISNAR 2002b;
ICSU 2002; Agricultural Biotechnology
Country Case Studies, Persley and MacIntyre, 2001;
Serageldin and Persley, 2003).
New
scientific discoveries in modern genetics, and particularly gene technology,
also provide options for the targeted introduction of transgenic
strains that are genetically modified for one or more traits. Transgenic
strains are produced by means of recombinant
DNA technologies (gene technologies) that enable the movement of
genes between species that do not normally cross in nature. Although
transgenic strains of various species of crops, trees, livestock and
fish have been developed experimentally, only transgenic crop varieties
are in widespread commercial use in agriculture today.
Agrobacterium-mediated
gene transfer in plants
In
plants, the process of genetic engineering was driven by the discovery
that a common soil borne bacterium and plant pathogen, Agrobacterium
tumifaciens, had a means by which it naturally transferred some
of its own bacterial DNA into targetted plant cells, and this transfer
and integration of bacterial DNA into the plant cells then caused the
plant cells to produce new compounds for the bacterium to use. It is
this naturally occurring transformation process that provided the scientific
basis for genetic engineering in plants. A
recent report by the French Academies des sciences
(2002) highlights the importance of this fundamental discovery
about Agrobacterium, as the basis for genetic engineering in
plants.
Agrobacterium
is now being used as a biological transfer agent to move one or
more genes from bacteria to plants, from plant to plant, and theoretically
from any other organism into plants. For example, insect resistant plants
contain toxin-producing genes from the bacterium, Bacillus thuringensis
(Bt) introduced into cotton, corn and other crops. Herbicide-tolerant
soybean contains genes isolated from soil-borne bacteria. A modified
strain of Agrobacterium tumifaciens is also being used
for the biological control of crown gall disease, the first genetically
modified organism to be released into the environment for commercial
use (Kerr, 1991).
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Commercial
cultivation of transgenic crops
The
first transgenic plants were produced experimentally in 1983, by means
of Agrobacterium-mediated gene transfer. The commercial cultivation
of transgenic crops began in 1995. By 2002, there were approximately
58.6 million hectares of genetically modified crops growing in sixteen
countries (ISAAA
2002b). These crops are mainly soybean, corn, cotton and oil
seed rape (canola), with resistance to certain insects and/or herbicide
tolerance (Figure 2.1). Many
other crop/trait combinations are under investigation.
Figure
2.1 Commercially cultivated genetically modified crops 2002
Source:
ISAAA CropBiotech Briefs Vol.3 No.1, 2003
Broadly,
the first wave of genetically modified crops, which are in commercial
use, address production traits; the second wave, which are mainly under
development, address quality and/or nutritional traits; and the third
wave address complex stress response traits and novel products able
to be produced in plants. The scientific basis of dealing with each
of these groups of traits is increasingly complex (ICSU
2002).
Several
socio-economic studies have assessed the benefits derived from specific
applications of genetically modified crops and other applications of
modern genetics in agriculture. For example, the benefits derived from
Bt cotton are documented in several countries, including Australia,
China, South Africa and the USA (eg
ISAAA 2002a; Pray et al 2002, Pardey
et al 2002).
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Emerging scientific discoveries for addressing complex traits
Most
characteristics of food are controlled by more than one gene. Thus taste,
aroma, colour, nutritional composition and other aspects of food quality
are the result of complex biochemical reactions within the plant before
and after harvest. Emerging scientific developments are enabling complex
traits that controlled by multiple genes to be addressed, with the intention
of developing new products of potential value for food and agriculture,
human health and the environment (for
examples, see Table 2.1). The attractiveness of the new targets
is tempered by the fact that they are technically difficult, requiring
the expression and control of several genes, which are often involved
in different biochemical pathways. The scientific basis of these developments
in genomics, proteomics
and metabolomics and related areas is reviewed in a companion ICSU
publication on Biotechnology and
Sustainable Agriculture (ICSU
2002).
Table 2.1.
Complex traits being addressed through emerging science
