Agriculture Reference
In-Depth Information
It also seeks to prevent gene flow from transgenics to wild species and to prevent
unwanted effects on wildlife.
Reviewing the rapid adoption of transgenic herbicide- and insect-resistant crops, it
appears that farmers are adopting these new crops for reasons of economics and safety.
In most cases there are long-term benefits from reduced soil erosion.
12.5
FUTURE OF TRANSGENIC CROPS
The trend in transgenic crops is easily seen in Table 12.2. Additional crops are being
developed to increase profitability and streamline production. A few crops are being
developed with enhanced grain composition for more efficient animal gains or
reduced environmental pollution.
An example of meeting both goals is the development of low-phytate maize. Up to
80 percent of the phosphorus in maize grain is bound as phytic acid. Animals that eat
this maize are not able to digest this phosphorus due to a lack of the phytase enzyme in
their stomach. As a result, most of the phosphorus contained in normal maize passes
through the animal and is excreted. This in turn produces high levels of phosphorus
in the manure collected in lagoons and spread on crop fields. Phytic acid also complexes
other nutrient elements, such as zinc, causing potential deficiencies in the diet of swine.
Varieties of maize with low levels of phytic acid are more readily digested by swine and
poultry, resulting in more complete utilization of the feed and less contamination by
high phosphorus manures.
One problem being addressed by regulatory agencies is the potential for escape of
transgenic crops into the wild and competing with native plants. In most cases domesti-
cated crops have lost many traits needed to compete in a wild, or feral, state. An
example being debated at the time of this writing is that of herbicide-tolerant creeping
bentgrass. This grass is widely used on golf courses. Pure, weed-free stands of bentgrass
could be easily maintained by simple applications of herbicide once a year. However,
Creeping Bentgrass can become feral, or grow in the wild. If this variety escapes, it will
not be controllable by at least one herbicide. There are fears that it could hybridize with
near relatives in the wild and pass on herbicide resistance to other types of grasses that
are more invasive. Other crops that can survive in the wild are also unlikely to be
released in transgenic forms.
12.6
TRANSGENIC ANIMALS
In addition to the selection of domesticated animals for specific traits, some animals
have been bred to develop traits useful in medicine. The most notable case is the
laboratory mouse. Over many years, researchers have identified mutants with debilities
or qualities that make them especially useful for studies of human diseases. The first
transgenic mice were born in 1980. By selecting specific gene sequences to insert, it
is possible to produce a mouse with natural hypertension, diabetes, premature aging,
and many other defects. It then becomes a problem of developing treatments for the
condition without complications of associated problems.
