New wheat varieties will provide better control to prairie farmers
battling the recent rise in wheat stem sawfly infestations, says Ron
DePauw, a wheat breeder at Agriculture Canada’s Semiarid Prairie
Agricultural Research Centre, or SPARC, in Swift Current, Sask.
DePauw’s team is developing new spring wheat lines with greater stem
solidness, a trait that reduces sawfly damage. AC Abbey was one of the
first products of this effort. It is a semi-solid stemmed variety that
first became widely available this past growing season.
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While not immune, AC Abbey has enough resistance to reduce sawfly
damage by 75 percent compared to susceptible varieties.
Researchers are working on several other wheat lines with greater
sawfly resistance and a better quality package, with the first expected
for registration in one or two years.
“Female sawfly insert their eggs into the hollow stem of the wheat
plant, and the damage is caused by the larvae that develop inside the
stem,” DePauw said.
“Wheat with higher stem solidness reduces the sawfly population in
several ways. Eggs are crushed during egg laying, larvae have greater
difficulty tunnelling within solid stems, larvae have less chance of
surviving the winter and females have reduced fertility the following
spring.”
DePauw said current varieties with greater sawfly resistance come with
some disadvantages.
AC Abbey produces up to 0.8 percent less protein than newer
hollow-stemmed wheat, while older solid-stemmed varieties such as AC
Eatonia carry a large yield penalty.
The new sawfly-resistant lines under development feature an improved
degree of stem solidness and a better overall agronomic and quality
package. To keep improving the package, researchers are investigating
new sources of stem solidness, including those found in durum lines,
DePauw said.
“The original source of solidness was S-615, a wheat from Portugal. All
common wheat in North America with stem solidness can be traced back to
this original source. Part of our research is to come up with
alternatives, so even if pests overcome S-615, or the gene breaks down,
we will still have another source.”
He said in the past 10 years researchers have tried to simplify the
inheritance of stem solidness genes to two-gene dominant types from
three-gene recessive types, which results in more plants with solid
stems.
“We’ve made very good progress in getting this alternative source of
solidness expressed in wheat.”
Long-term effort
DePauw said progress is based on a long-term wheat germplasm collection
and development effort that began in the 1930s with SPARC wheat breeder
Harold (Shorty) Kemp and director L.B. Thompson.
“The sawfly is an old problem our researchers have battled for much of
the century,” he said.
“They didn’t have the technology in the old days to make the progress
we can today, but the germplasm they collected and developed is what
ultimately led to our success. It’s a classic example of the
contribution of long-term germplasm development to Canadian
agriculture.”
DePauw said trap cropping is a good strategy – seeding the perimeter of
the field to solid-stemmed varieties while seeding the inside to a
high-performing variety. The sawfly is a weak flyer and can often be
confined to the outer nine to 18 metres of wheat fields.
“However, when sawfly populations are very large, this does not work
effectively.”
