Canada
July 8, 2009
In the future, farmers may be
eliminating one pesticide application on their canola.
Researchers at
Agriculture and Agri-Food Canada's Saskatoon Research Centre
are developing 'hairy' canola plants that prevent flea beetles
from feeding on the leaf and stem surfaces of newly emerged
canola seedlings.
This physical barrier means flea beetle resistance will be built
into the plant, with little or no need for an insecticide
application.
Margie Gruber, the research scientist leading the project,
received funding from the
Western Grains Research Foundation (WGRF) and various canola
funding agencies to develop germplasm that is flea beetle
resistant.
"The trait we were looking at is trichomes, which are plant
hairs," says Gruber. "Lots of plants have trichomes. Canola has
a few, but related species like mustards have a lot more. We're
interested in seeing if we can stimulate the plant to produce
more on the seedling leaves and stems."
Two types of trichomes are commonly found on plants. The first
type is a bumpy protuberance on the plant surface that often
releases various plant chemicals, like in the mint family. The
other kind sticks out a bit farther.
"We wanted to look at the ones that stick out. Those types of
trichomes are in plant species related to canola, as well as in
Arabidopsis - a model plant that has had a lot of research done
on the genetic basis for the development of trichomes," says
Gruber.
The trichomes interfere with feeding patterns of the tiny flea
beetles.
"It's a specialized insect, with specific behaviors it undergoes
when testing a plant surface before eating it. If a full series
of behaviors are not completed, it starts over or moves off the
plant," she says.
Gruber has inserted genes from Arabidopsis into canola plants,
to over-express trichome production. Over-expressing the genes
in Arabidopsis increased trichome production by about fifty
times, but over-expressing the same genes in canola produced
about 1,000 times the number of trichomes.
"We were trying to put the hairs on any and all parts of the
seedlings. What we achieved was to put them on the young leaves
and stems. The cotyledons were still smooth, but they seemed to
be more flea beetle resistant, even without the trichomes. So
the genes that we used also modified the plants in some way to
be more resistant," she says.
Gruber already has lines developed with significantly reduced
flea beetle feeding damage, but the trichomes don't yet have any
branches on them.
"We're currently testing genes that would make branches on the
trichomes. In Arabidopsis, they can have three to four branches
depending on where they grow. In canola there are no branched
trichomes at all," she says.
"We feel branching will increase the density of the trichome
mat, so flea beetles that can find a little bare spot and can
burrow down wouldn't be able to do that nearly as well. The
average is three branches, but we can make mutants with six or
seven. It's just a matter of testing and isolating a number of
different Arabidopsis trichome branching genes."
"We're using Arabidopsis genes to promote trichomes in canola
and also we're trying to understand what's going on with canola.
That may lead to methods to develop trichomes in canola without
genetic engineering."
Gruber says it will still take some time to develop canola
plants that are worthy of going into a plant breeding program.
Current breeding lines with the hairy characteristics mature
about a week later than commercial canola varieties.
"We had these plants out in the field in generation three and
four and they were small, but they gave good flea beetle
resistance. They're bigger now in generation seven, but we still
want to improve the seedling vigor," she says.
"When the agronomics of those lines are close to the agronomics
of current varieties, then we'll provide that material to plant
breeding companies. That might be in three years."
She says this type of insect resistance will be a more robust
resistance that won't break down or have resistant insect
populations develop, compared to things like Bt resistance.
Because it's a physical resistance rather than a biological
system, it will be more difficult for the insects to adapt to.
Gruber says when the final developments are complete and the
trichomes have branches, farmers shouldn't have to use any
chemical flea beetle control at all.
The Endowment Fund, the original core fund of WGRF, has
supported more than 200 research projects since 1983. It funds
project on cereal grains, as well as oilseeds, pulse crops and
other commodities. Research Reports on many of these projects
are available on the WGRF web site.
For more information on the project check the WGRF Web site at
www.westerngrains.com. |
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