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Rare germplasm leads to sawfly-resistant wheat

Western Canada's new sawfly-resistant wheat varieties are arriving with long and age-worn passports, detailing stops from old-world Portugal to modern day Swift Current.

Improved sawfly-resistant wheat varieties are set to hit farmers' fields, with AC Abbey leading the charge. But the story of this progress began long ago, says breeder Dr. Ron DePauw, and it illustrates the powerful role of international germplasm in today's cereal breeding programs.

"The sawfly is an old problem our researchers have battled for much of the century," says DePauw, head of cereal research at Agriculture and Agri-Food Canada's Semiarid Prairie Agricultural Research Centre (SPARC) in Swift Current.

"The female sawfly inserts its eggs into the hollow stem of the wheat plant, and the damage is caused by the larvae that develop inside the stem," says 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."

The story began in 1929, when SPARC wheat breeder Harold (Shorty) Kemp observed that the solid-stem Golden Ball durum was less seriously damaged by sawflies than Marquis, Reward, and other bread wheats.

Solid-stem genetics cut damage

"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."

At the time, there was no technology to transfer the solidness of Golden Ball durum genetics into bread wheats, which desperately needed the sawfly resistance. This sent Kemp on a search for other sources of solid-stemmed bread wheat germplasm. In 1930, he planted seed from two heads of wheat with semi-solid stems that he obtained from the United States Department of Agriculture.

"This strain, C. I. 7265-12, was of Egyptian origin," says DePauw. "But the strain must have had a variable genotype, because only a few offspring had solid or even semi-solid stems. So it was back to the drawing board."

As luck would have it, L.B. Thompson, SPARC Director, recalled seeing some solid-stemmed bread wheats in his native New Zealand. "Thanks to L.B. Thompson, during the winter of 1931-32, Kemp obtained 38 varieties from a Dr. Frankel of Christchurch, New Zealand," says DePauw. "Most of them had been collected in Spain, Portugal and Morocco, and two of them were solid-stemmed."

S-615, one of the Portuguese varieties, proved the best for crossing with Canadian-adapted cultivars. More than a decade of crosses later, breeding work with this variety led to Rescue, the first Canadian variety with improved sawfly resistance. More decades of crossing led to new varieties such as AC Eatonia and AC Abbey, which can reduce sawfly damage by 75 percent.

The greatest progress is yet to come. The outstanding solidness of Golden Ball durum wheat, which could not be transferred 60 years ago has now been transferred successfully by Dr. Fran Clarke, Dr. Taing Aung and DePauw, using goat grass germplasm and new plant breeding tools. This will lead to further improvements in future varieties.

"It's a classic example of the contribution of long-term germplasm development to Canadian agriculture," says DePauw.

For more information on sawfly-resistant wheat, visit the Western Grains Research Foundation website at www.westerngrains.com

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