Lincoln, Nebraska
May 24, 2007
In a project that began about a
dozen years ago, University of
Nebraska-Lincoln scientists discovered a gene that has been
used to create broadleaf crops that tolerate spraying with the
popular herbicide dicamba. Now, even as an industry partner is
working to bring dicamba-resistant crops to market, these plant
scientists are continuing to explore new and expanded uses for
the technology they discovered.
The availability of dicamba-resistant crops means that farmers
soon will have more options for controlling weeds in broadleaf
crops such as soybeans, canola, cotton, tobacco and vegetables.
The UNL team, headed by biochemist Don Weeks, outlined its
discoveries on the molecular, cellular and biochemical processes
involved in creating dicamba-resistant crops in the May 25 issue
of Science, the international weekly journal.
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Two
rows of soybean plants are shown eight days after they
were sprayed with dicamba. The plants on the left, which
contain the dicamba-resistant gene, are thriving. The
plants on the right died. |
Dicamba-based herbicides, sold
under trade names such as Banvil and Clarity, are relatively
inexpensive and easy on the environment because the chemical
disappears quickly in plants and soil. But like all broadleaf
herbicides, dicamba kills broadleaf crops as well as their weedy
cousins so its use presently is limited to corn and other grassy
crops.
The UNL team identified soil bacteria that break down dicamba
and isolated the gene responsible for imparting resistance.
Plant Scientist Tom Clemente, head of the university's Plant
Transformation Core Facility, helped the team insert this gene
into a plant's chromosomes, successfully transferring dicamba
resistance to the plant.
They also discovered that they could modify the gene to target
the DNA of the plant chloroplast, where photosynthesis occurs.
This approach has significant practical implications. Since
chloroplast genes are inherited through the material side, not
through male pollen, it eliminates the chance that resistance
could inadvertently spread to other plants through pollen.
The team's genetic modification technique worked in both lab and
field trials. For example, soybeans carrying the
dicamba-resistant gene were unharmed by dicamba sprayed at a
rate of 2.5 pounds per acre, about 10 times the normal
application rate.
"There are a number of levels at which we think this technology
will be useful," Weeks said. "It will certainly allow for
excellent control for broadleaf weeds in broadleaf crops like
soybeans and cotton ... Controlling broadleaf weeds in broadleaf
crops has always been a challenge and often quite expensive."
The new technology, Weeks added, also will help strengthen
integrated weed management strategies.
"Importantly, we think that this technology will help to extend
the lifetime of the Roundup Ready technology," he added. Some
Roundup-resistant weeds have emerged in recent years, but
working dicamba products into a weed-control strategy with
Roundup could help counter that trend and lead to more complete
weed control.
In addition, development of dicamba-resistant crops should
further encourage use of conservation tillage practices that
decrease soil erosion and foster more sustainable and
environmentally sensitive farming, Weeks said.
UNL has patented this technology. In 2005 UNL signed an
exclusive licensing agreement with
Monsanto Company to develop crops
tolerant to dicamba, using UNL's technology.
"Monsanto is clearly moving forward with this technology, taking
it through the regulatory processes at USDA, EPA and FDA, as
well as conducting a number of field trials," Weeks said.
Dicamba-resistant crops aren't expected to be commercially
available until early in the next decade. In the meantime, Weeks
said, the agreement is supporting his team's continuing
dicamba-resistance research – a key payoff of such
technology-transfer agreements between universities and private
industry.
"We're testing for efficacy in other crops; that research is
looking promising," the Institute of Agriculture and Natural
Resources biochemist said. "We also have explored some other
aspects of this technology and have exciting new observations
that we soon hope to have patented."
Monsanto is funding the research, which is conducted through the
university's Agricultural Research Division, a part of the
Institute of Agriculture and Natural Resources.
Other news
from Monsanto Company |
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