With Fusarium Head Blight (FHB) and other disease concerns eating resources and wrestling for attention, wheat breeding programs face an increasingly tough balancing act to get the right package of traits in new varieties, say two leading wheat breeders.

"With all the priorities we deal with now, adding even two to four target genes can make a breeding strategy unmanageable," says Dr. Ron DePauw, wheat breeder at Agriculture and Agri-Food Canada's (AAFC) Semiarid Prairie Agricultural Research Centre in Swift Current. "An additional three genes is likely the minimum we're looking at for Fusarium Head Blight. To handle that capacity, you either need a large amount of additional resources or you need to find traits to drop that are controlled by an equivalent number of genes."

Every time wheat breeders add a trait to their target list, the segregating population size they require to identify the full package of desired productivity, quality and disease traits increases exponentially, explains Dr. Rob Graf, wheat breeder at AAFC's Lethbridge Research Centre. "To give a rough example, if you add one gene difference as a requirement, you need to increase your segregating population size to four times its current size. If you add two gene differences, you need an increase of 16 times the original size. For three gene differences, the size requirement is 64 times, and so on."

DePauw and Graf offer perspective on the breeding challenge of disease resistance in the new May edition of Western Grains Research Magazine, available on the Western Grains Research Foundation (WGRF) Web site: www.westerngrains.com. Western Canadian wheat and barley growers are major investors in wheat and barley breeding research through the Wheat and Barley Check-off Funds, administered by WGRF. The Research Magazine offers "Ideas and issues for farmer research investors."

Graf, who breeds winter wheat, and DePauw, who works primarily on hard red spring wheat, explain the different approaches wheat breeders take when working on different wheat classes.

In the case of winter wheat, which is presently a smaller acreage wheat class, researchers have taken a step-by-step approach toward varieties with resistance to multiple diseases. "If you look back 15 years in winter wheat, we were at a stage where the main variety was Norstar, which doesn't have much disease resistance," says Graf. "As a result, our program and others have concentrated on building in traits like resistance to bunt, wheat curl mite and the rusts, along with bringing in a semi-dwarf stature and incorporating other important non-disease traits.

"We're at a point now where we've seen good progress with that initial phase. The real challenge now is to start combining those resistances into single varieties, so we have an overall protection package."

For the long-standing, big-acreage hard red spring wheat class, Canada Western Red Spring, a major focus for researchers is maintaining the solid disease resistance package already in the class. "Often, once resistance is achieved, there's a perception that we can leave that disease priority and move on to something else, but that's not the case," says DePauw. "Pathogens change over time and new strains emerge, so you always have to keep up to date. You also don't want to spread yourself too thin by relying too heavily on one or two sources of resistance.

"A good example is stem rust and leaf rust, which occur annually in the Red River valley and on the eastern side of the Prairies. This year, we put forward a line for registration, HY476, which features the first deployment of a new gene for resistance to common bunt. This gene, called Bt 8, is needed because all current variety resistance is based on a single gene, Bt 10, which is expected to lose effectiveness over the next several years."

The May edition of Western Grains Research Magazine also includes two other feature stories - one on what variety survey results indicate for farmer-funded research, and a second on key trends and issues highlighted in two newly updated reports on wheat and barley breeding.

Western Grains Research Foundation is funded and directed by Western crop producers, and allocates approximately $4 to $5 million annually to research through the Wheat and Barley Check-off Funds and a separate $9 million Endowment Fund.