Saskatoon, Saskatchewan
October 15, 2002

Prairie farmers battling the recent rise in wheat stem sawfly infestations will soon have better control options in the form of new wheat varieties, says Dr. Ron DePauw, wheat breeder at Agriculture and Agri-Food Canada's (AAFC) Semiarid Prairie Agricultural Research Centre (SPARC) in Swift Current.

DePauw and his team are developing new spring wheat lines with greater stem solidness, a trait that reduces sawfly damage, he says. One of the first products of this effort is AC Abbey, a semi-solid stemmed variety that first became widely available this past growing season. While not immune, AC Abbey has enough resistance to reduce sawfly damage by 75 percent compared to susceptible varieties.

Several other potential wheat varieties with higher sawfly resistance and a better quality package are in development, 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," explains DePauw. "Wheat with higher stem solidness reduces the sawfly population in several ways - eggs are crushed during egg laying, larvae have greater difficulty tunneling within solid stems, larvae have less chance of surviving the winter and females have reduced
fertility the following spring."

There are some drawbacks to the current varieties with greater sawfly-resistance, DePauw says. AC Abbey produces up to 0.8 percent lower protein than newer hollow-stemmed wheat, while older solid-stemmed varieties such as AC Eatonia carry a large yield penalty. But the new sawfly-resistant lines under development feature both an improved degree of stem solidness and a better overall agronomic and quality package.

Along with DePauw, the major research effort to breed sawfly-resistant wheat varieties is led by SPARC colleague Dr. Fran Clarke and Dr. Taing Aung of the AAFC Cereal Research Centre in Winnipeg.

To keep improving the package, the researchers are investigating new sources of stem solidness, including those found in durum lines, says DePauw. "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."

"Our strategy over the past 10 years has been to simplify the inheritance of stem solidness genes from three-gene recessive types to two-gene dominant types, which results in more plants with solid stems," says DePauw. "We've made very good progress in getting this alternative source of solidness expressed in wheat." The breeding effort is supported by wheat producers through the Wheat Check-off Fund, administered by Western Grains Research Foundation, and the Federal Matching Investment Initiative Fund.

The current 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, and has involved many researchers, says DePauw. "The sawfly is an old problem our researchers have battled for much of the century. 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."

A good strategy for using the sawfly resistance in current varieties is trap cropping  - seeding the perimeter of the field to solid-stemmed varieties, while seeding the inside to a high-performing variety, he says. The sawfly is a weak flyer and can often be confined to the outer 30 to 60 feet of wheat fields. "However, when sawfly populations are very large, this does not work effectively."

The Wheat Check-off Fund allocates approximately $3 million annually to wheat breeding research. It is administered by the farmer funded and directed Western Grains Research Foundation.