Twenty years of breeding improvement has produced a series of top winter wheat varieties showing good resistance to common rust diseases, says a well-known University of Saskatchewan (U of S) breeder.

"Farmers today certainly have access to several cultivars with more than adequate levels of rust resistance," says Dr. Brian Fowler, a winter wheat breeder at the U of S Crop Development Centre (CDC) in Saskatoon. "We can't let our guard down, but it is one disease issue we have under control." Prairie winter wheat breeding programs are funded in part by the Wheat Check-Off Fund, administered by the Western Grains Research Foundation (WGRF).

Five of the newest hard red winter wheat varieties are rated as either IR or R (Intermediate Resistance or Resistant) to both stem and leaf rust. The selection gives producers of the estimated 700,000 acres of winter wheat a good line of defence against the disease, which can take a heavy toll on the crop if left unchecked.

Newer varieties such as CDC Buteo, CDC Falcon, CDC Raptor and CDC Harrier, all developed in Fowler's breeding program, along with McClintock from Dr. Anita Brûlé-Babel's breeding program at the University of Manitoba (U of M), have good rust resistance.

Other new varieties such as CDC Osprey, as well as AC Bellatrix and AC Radiant developed by Dr. Rob Graf at Agriculture and Agri-Food Canada's Lethbridge Research Centre (LRC), provide good agronomic performance and grain quality, but are suited for the non-rust hazard area of the Prairies.

At one time, stem and leaf rust were considered the most serious diseases, respectively, affecting the Canadian wheat crop. Varieties registered before the 1990s had decent agronomics and yields, but little rust resistance. Breeding over the past 25 years has dramatically reversed the situation in winter wheat varieties.

While both diseases can have a significant economic impact on the crop, stem rust poses the greatest threat to the Prairie winter wheat crop, says Fowler. Both diseases over-winter in Mexico and the southern United States - with spores carried on prevailing winds into Western Canada in early summer.

Because of winter wheat's early production cycle, leaves of the crop are usually past their prime point of susceptibility by the time leaf rust disease spores reach Canada, usually in July. But the crop is more susceptible to stem rust, says Fowler.

"Crops without rust resistance are especially vulnerable if producers aren't using best management practices," he says. "The crop can get hammered the next year if it is seeded late or gets a slow start due to poor seedbed moisture." He points to examples where susceptible crops seeded in early September went on to yield about 50 bushels per acre, while a neighbouring field seeded 15 days later, only yielded 18 bushels per acre in the severe rust year of 1986. He adds, "With only that much difference in time, stem rust can do a lot of damage."

Selecting lines with good rust resistance is one of the main criteria in breeding, says Brûlé-Babel, who runs a leaf and stem rust nursery as part of the wheat breeding program at the U of M. She screens about 6,000 lines of winter wheat annually, for rust resistance.

"Nothing gets through our breeding program without rust resistance," she says. "If a line moves forward, it's because it shows resistance to the disease." Similar to Fowler's approach in Saskatoon, potential lines are inoculated with the disease to see how they perform.

Along with their own material, the U of M and U of S nurseries screen lines for the central and western co-op variety trails for Dr. Don Salmon, plant breeder with Alberta Agriculture, Food and Rural Development's Field Crop Development Centre in Lacombe and for Dr. Rob Graf at LRC.

The producer-funded Wheat Check-off Fund, administered by WGRF, allocates more than $3 million annually to wheat breeding programs in Western Canada.