Agriculture Reference
In-Depth Information
few benefits to the farmer, but it has great potential to reduce blindness in children in
Africa. Conventional breeding has often been able to select for color or size preferred
by consumers, but transgenic technology greatly expands the modifications that can
be made.
Third-generation transgenic crops have been designed to produce pharmaceutical
compounds or products with specific qualities for industry. Sometimes called
“pharming,” the production of these crops offers economic advantages for the manufac-
ture of products that are difficult to obtain through normal production methods. An
example is human growth hormone normally obtained from pituitary glands of large
numbers of cadavers. This hormone can be produced in significant quantities by trans-
genic maize at low cost without risk of transmissible diseases or contamination.
Today's crop plants are not the same as their wild progenitors. Humans have made
changes that have resulted in loss of functions for the plant concerned. In some cases
our crops are so different they depend on humans for their survival. Modifications
now being made in crop plants are significantly different from those made over the
past several thousand years. Current transgenic changes involve addition of traits to
domesticated plants. How this will affect future crops remains to be seen.
12.4
TRANSGENIC CROPS
There are currently many transgenic crops being grown by farmers. Many more are
in the development stage or ready for release to producers. Transgenic crops produced
in 2004 or approved for marketing in various countries of the world are shown in
Table 12.1. Most of these crops have been modified with traits to make their cultiva-
tion easier (herbicide tolerance) or to resist diseases or insects. Canola, rice, soybean,
and sugar beet have been modified to make modified, or very different, end products.
T A B L E 12.1. Transgenic Crops Produced in 2004
Crop
Modified Traits
Canola
Herbicide tolerance, high laurate content, and high oleic acid content
Carnation
Herbicide resistance, delayed senescence, modified color
Cotton
Herbicide tolerance, insect resistance
Maize
Herbicide resistance, insect resistance
Papaya
Resistance to papaya ringspot virus
Potato
Colorado potato beetle resistance, potato leafroll virus, potato virus Y
and potato virus X resistance
Rice
Vitamin A content
Soybean
Herbicide tolerance, high oleic acid content
Squash
Resistance to watermelon mosaic virus and zucchini yellow mosaic virus
Sugar beet
Resistance to beet necrotic yellow vein virus, herbicide tolerance,
fructose production
Tobacco
Herbicide tolerance
Tomato
Herbicide tolerance, delayed ripening
Source: Adapted from Ref. 10.
