Special Feature newsletter article, April 2000
asked questions regarding the production of transgenic crops
The transgenic crop, also known as
genetically modified organism (GMO), debate has created many new issues for
production agriculture. Most are not unique to transgenic crops, they are
just the beginning of differentiated markets based on a wide range of new
Grain Quality Initiative has assembled this question/answer checklist to help
you with planting decisions. Look for more updates and information throughout
the 2000 season.
by Dale Farnham, Former Assistant Professor of Agronomy
to plant only conventional hybrids and varieties on my farm; however, my neighbor
plants a mix of conventional and transgenic crops . What is the potential
for cross-pollination between my neighbor's crops and mine?
If the crop
in question is soybean, it's a fairly safe bet that there will be no cross-pollination.
The soybean plant produces a perfect flower (each flower contains both male
and female reproductive structures) and is selfpollinated. There is little
chance of cross-pollination in soybean.
If the crop
in question is corn, chances for crosspollination increase considerably (the
corn plant is largely self-pollinated, also, however a certain degree of cross-pollination
is common in all corn fields). The corn plant produces separate flowers for
the male and female reproductive structures (male flower, or tassel, at the
top of the plant and the female flower, or ear, located midway up the stalk).
An average corn plant will produce between two million and five million pollen
grains. An average ear will produce 750 to 1,000 ovules (and silks). That
means that there are approximately 2,000 to 5,000 pollen grains produced for
shed from the tassel and falls onto the silks of the ear, a distance of approximately
three to five feet. Obviously, not all of the pollen will fall directly onto
an awaiting silk. Some of the pollen will be picked up and transported by
the wind and may pollinate silks on neighboring plants, some will fall onto
the leaves, some will be picked up and carried away by insects or birds, and
some will fall onto the ground. The distance that pollen can be carried on
the wind is the real question.
will pollen travel on the wind?
have shown that the bulk of a corn plant's pollen will fall within a 20-foot
radius of the plant. However, some may be carried much farther, perhaps up
to a quarter of a mile or farther.
It is important
to remember, however, that pollen shed is not a continuous process. It turns
on and off in response to the environmental conditions at the time. Thus,
very little, if any, pollen is being shed on rainy days, on windy days, on
extremely hot days, or on extremely cool days. In addition, the average life
of a pollen grain is only about 20 minutes, so it needs to do its work quickly
before it loses its viability.
be an appropriate separation distance between the conventional and transgenic
crops to avoid potential cross-pollination?
industry uses a separation distance of 660 feet (40 rods) for seed fields
by convention. There is nothing
magical about this distance, however. Obviously, the greater the distance,
the less likely the chance for crosspollination.
steps should be taken to reduce the chances of cross-pollination from neighboring
talking with your neighbor(s). Find out what hybrids are intended to be planted
in each field and design a layout that will reduce the possibility of cross-pollination.
Also, consider how each field lies with regard to the prevailing winds.
buffer strips (non-transgenic corn hybrid or an alternate crop such as soybean
or forage) may need to be factored into the field layout. At harvest time,
rows directly adjacent to the neighbor's field may need to be harvested separately
and marketed or used differently, perhaps fed onfarm or sold to a local feed
other preventive measures that may help reduce the chances of contamination
can occur at any of a variety of points throughout the production and marketing
channels, from the seed provider to the end-user. Thus, cleanliness and identity
preservation will be critical factors in keeping contamination to a minimum.
prepare field plans and designate where specific transgenic and non-transgenic
crops will be grown. Draw detailed field maps that show the location of each
hybrid or variety. Design the plan so all transgenic hybrids or varieties
are planted either first or last, thus reducing the amount of time necessary
to clean out the planter.
time to adequately clean the seed hoppers and metering mechanisms of the planter.
A single kernel of corn seed that is left in the planter has the potential
of producing several thousand kernels of unwanted, contaminated grain. Retain
tags from seed bags for each hybrid or variety planted. At harvest time, harvest
transgenic and nontransgenic crops in the same manner in which they were planted
- one at a time - to reduce the amount of time required to clean the combine
and transporting equipment. Rely on your maps to help keep the different types
of grain segregated and identity preserved.
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