Saskatoon, Saskatchewan
June 30, 2003

A team of Canadian Prairie researchers plans to help farmers cut down on the millions of dollars lost annually due to the wheat stem sawfly, by putting a squeeze on the insect - literally.

The researchers, funded in part by the Wheat Check-off Fund administered by Western Grains Research Foundation, are developing a new wave of spring wheat varieties with greater stem solidness, a trait that reduces sawfly damage by leaving less room for larvae to develop and "tunnel" inside the wheat stem.

AC Abbey, the first variety in this wave, is available to producers, and BW776, a new line featuring improved quality, was recently recommended for registration, says Dr. Ron DePauw, wheat breeder and head of cereal research at Agriculture and Agri-Food Canada's (AAFC) Semiarid Prairie Agricultural Research Centre (SPARC) in Swift Current. Further advances are also on the way, with the introduction of a new source of sawfly resistance recently transferred from durum wheat into spring wheat.

"This new generation of spring wheat with greater stem solidness offers growers a major improvement in sawfly resistance, with a 50 to 75 percent reduction in sawfly-toppled wheat compared to susceptible varieties," says DePauw. "AC Abbey is the first product of this generation and it gives growers an important option to reduce their sawfly risk. The varieties that follow AC Abbey over the next several years will aim for further improvements in the overall quality and agronomic performance package."

Along with DePauw, the spring wheat breeding effort toward greater sawfly resistance includes contributions from quantitative geneticist Dr. Fran Clarke, molecular geneticist / pathologist Dr. Ron Knox and durum breeder Dr. John Clarke of AAFC Swift Current; agronomist Brian Beres, entomologist Dr. Hector Carcamo, wheat breeder Dr. Rob Graf and agrometeorologist Dr. Sean McGinn of AAFC
Lethbridge; and cytogeneticist Dr. Taing Aung of AAFC Winnipeg.

The benefits of varieties with greater stem solidness are highlighted in a recent three-year study that measured the performance of top wheat varieties under sawfly infestation conditions, says Beres. On average, AC Abbey experienced 6.5 percent annual cutting under high sawfly pressure, compared to around 70 percent cutting for susceptible varieties. There was also one noteable variety in the mid range - McKenzie, a variety developed by Saskatchewan Wheat Pool, which experienced a three-year average of 23 percent cutting.

Lodging resistance, the ability of stronger strawed wheat to withstand toppling, is a significant factor in reducing sawfly damage, says Carcamo. But the major factor in varieties with greater sawfly resistance is stem solidness, otherwise known as pith expression. "We know that the nature of resistance in wheat is mostly mechanical. The main thing that prevents sawfly damage and survival seems to be when eggs and developing larvae are crushed by developing tissue or 'pith' inside the wheat stem. The wheat cultivars with the best resistance to the sawfly are the ones with a greater expression of this tissue, which restricts the amount of space or hollowness in the stem."

A drawback of AC Abbey is that it produces up to 0.8 percent lower protein than newer hollow-stemmed wheat, says DePauw. The new line BW776 offers similar sawfly resistance, along with the key advantage of higher protein potential.

As part of the effort to further improve the overall package, the researchers are working with a very promising new source of stem solidness derived from Golden Ball durum, says Clarke. "All common wheat in North America with stem solidness can be traced back to a single original source - the S-615 wheat line from Portugal. This leaves us vulnerable over the long-term if the sawfly is able to overcome S-615 or if the gene breaks down. Our new source of resistance is the result of an innovative approach to provide an alternative, by transferring the excellent stem solidness of Golden Ball durum into spring wheat lines."

The Golden Ball solidness trait was transferred using goat grass germplasm and new breeding tools, says Aung. Golden Ball-derived spring wheat lines could reduce sawfly damage by up to 90 percent compared to susceptible varieties, and the first of this material in expected to enter pre-registration tests within two years. "This material also has potential for improved rust and bunt resistance, bringing new diversity for genetic resistance to these diseases," he says.

The Wheat Check-off Fund, administered by Western Grains Research Foundation, allocates over $4 million annually to wheat breeding programs in Western Canada. The sawfly research effort is also supported substantially by government funds matched to these farmer dollars through AAFC's Matching Investment Initiative and royalties earned on WGRF funded cultivars.