Saskatoon, Saskatchewan
October 30, 2002

The wheat stem sawfly is set to meet its match - using innovative breeding techniques, Agriculture and Agri-Food Canada (AAFC) researchers have transferred the outstanding sawfly-resistant genetics of Golden Ball durum into Canadian spring wheat lines.

This progress is expected to lead to spring wheat varieties that reduce sawfly damage by over 90 percent compared to susceptible varieties, says Dr. Fran Clarke of the AAFC Semiarid Prairie Agricultural Research Centre (SPARC) in Swift Current, who led the research along with Dr. Ron DePauw of SPARC and Dr. Taing Aung of the AAFC Cereal Research Centre in Winnipeg. This effort was supported in part by the Wheat Check-off Fund, administered by Western Grains Research Foundation (WGRF), and the AAFC Matching Investment Initiative Fund

"This is an exciting development in our long battle with the sawfly," says Clarke, a quantitative geneticist. "Canadian wheat researchers identified the sawfly-resistance benefits of Golden Ball durum over 70 years ago, but it is only in the past few decades that we've had the understanding to successfully transfer the genetic basis of this resistance into spring wheat lines. We are now combining this excellent resistance into wheat lines that feature a full package of other high quality and agronomic traits, and we expect to have some of the first material in pre-registration co-op tests within two years."

The sawfly resistance of Golden Ball is derived from its high level of stem solidness, says Clarke. Sawfly damage is caused by larvae that develop inside hollow wheat stems, so varieties with greater stem solidness have greater resistance. "Stem solidness is much more prevalent in durum wheat, and Golden Ball durum particularly features significantly higher stem solidness than the best spring wheat sources."

The roots of the modern progress began in 1929, when SPARC agronomist Harold (Shorty) Kemp observed that the solid-stemmed Golden Ball durum was less seriously damaged by sawflies than Marquis, Reward and other popular bread wheats. At the time, the scientists were unable to transfer the genetics of Golden Ball into bread wheats, so Kemp and other researchers who followed focused instead on doing the best they could with existing bread wheat sources. This pioneering effort has led to modern varieties such as AC Eatonia and AC Abbey, which can reduce sawfly damage by 75 percent compared to susceptible varieties. Clarke says the genetics of Golden Ball durum will raise the bar on this resistance.

"We began this effort in 1994 and it has taken a lot of work, largely due to the inherent difficulty of crossing durum wheat with bread wheat," says Clarke. "Durum has a tetraploid chromosome number and is made of a set of chromosomes from what is known as the 'A' and 'B' wheat genomes. Its stem solidness is inherited as a dominant trait. By contrast, bread wheat has a hexaploid chromosome number and is made up not only of a set of chromosomes from the A and B genomes but also the 'D' genome from a wild wheat derivative. Its stem solidness is recessive due to interaction with genes in the D genome."

Previous efforts to transfer the solidness of Golden Ball into bread wheat were unsuccessful because a gene in the D genome suppressed this trait whenever durum was crossed with a bread wheat. But modern research has overcome this hurdle, says Clarke.

Dr. Eric Kerber of AAFC in Winnipeg, who had studied suppressor genes, helped the researchers locate and obtain seed from a valuable synthetic bread wheat produced by Dr. Ernie Sears at Columbia University, Missouri. This wheat contained a combination of genetics of both Golden Ball durum and a strain of wild wheat derivative goat grass. The D genome goat grass and the A-B genome Golden Ball had then been doubled to make a hexaploid wheat. Most importantly, these genetics contained a "non-suppressor" gene, which allowed the solidness of Golden Ball to be expressed in the bread wheat.

The challenge then fell to the Canadian research team to transfer these genetics into bread wheat lines that contained the necessary productivity and quality traits essential for growing on the Canadian Prairies, says Clarke. Dr. Taing Aung has facilitated and tracked the transfer using cytogenetics and double-haploid techniques, and the research team as a whole is making good progress.

"We are now within striking distance of getting the Golden Ball-derived resistance into registered Canadian varieties. The germplasm is being transferred into the high yielding, high protein cultivar, AC Elsa. The most difficult work is over, and now it's just a matter of plant breeding effort."

Further information on wheat breeding progress toward sawfly resistance is available on the Western Grains Research Foundation. 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.