Meristem: Wheat Science

Are the tables finally set to turn on Canada's most costly cereal disease? Leaders on the frontlines provided their views at the Canadian Workshop on Fusarium Head Blight.

In the 1993-94 crop year, Fusarium Head Blight emerged from the shadows to hit Canadian grain crops with a vengeance. Ten years and over $1 billion in losses later, it has become the most costly and challenging grain disease of the past 100 years.

Grain farmers, with little in the way of control options, have seen major reductions in yield, quality and, as a result, profitability. These problems, combined with concerns about Fusarium-produced mycotoxins, have reduced the supply of cheap grain feed for the livestock industry - particularly for the expanding hog industry. They have also added costs for and reduced the feasibility and profitability of other downstream uses and products of grains, including human food products and ethanol. Overall losses have ranged from $50 to $300 million annually since the early 1990s.

Despite this bleak picture, significant progress has been made behind the scenes. Researchers have made major strides in understanding the disease and developing control options. Most notable are Fusarium-resistant cereal varieties that after years of breeding work are now beginning to become available to farmers. Management strategies to reduce the risk have greatly improved and, for the future, molecular breeding and other innovative approaches promise advances in everything from forecasting to disease prevention and mycotoxin reduction.

However, for the most part, strong, broad-based tools and strategies to dramatically cut Fusarium losses remain at least several years away. This is a testament to the complexity of the disease and of genetic resistance, which is viewed as essential to long-term solutions.

In Canada, widespread recognition of the devastating losses and immense challenge Fusarium represents has led to the development of the Canadian Workshop on Fusarium Head Blight. This event, held every two years since 1999, is designed to bring together researchers, industry, extension and others interest groups from across Canada and beyond, to share ideas on Fusarium and co-operate toward common solutions.

The 3rd Canadian Workshop on Fusarium Head Blight was held Dec. 9-12, 2003, in Winnipeg, in the heart of Manitoba's Red River Valley, the region hardest-hit by the modern Fusarium problem. Over 20 speakers at the three-day event provided an overview of the latest progress, challenges and ideas. Here's a snapshot of their comments.

Getting the job done

"Not since the stem rust situation in the 1950s has such a concentration of effort been marshaled against one crop disease. Since the early 1990s, we now know quite a bit more about Fusarium resistance - the genetics of resistance and expression of resistance. But one of the concerns with a major effort like this is, will the funding support continue to be there? There's been a long history of funding for all kinds of biological research where down the road the money dries up or goes someplace else before sufficient work can be completed. I think, this time around with Fusarium, that's not going to be an issue. The FHB crisis has made a strong enough impression on those who hold the purse strings, that the effort to solve FHB is likely to continue for long enough to get the job done."

- Dr. Bob Stack, Plant Pathology Department, North Dakota State University, Fargo.

Call to urgency

"We can't afford slow advances. We must deliver results to the producers. Our understanding of the mechanisms of resistance and tolerance of plants to pathogens remains minimal for many major diseases. The endeavor of deciphering those mechanisms is often justified by an academic interest, but when dealing with FHB, there are more compelling priorities. Specifically, we need to concentrate on finding quick, practical means for reducing disease incidence and damage. As part of this, we should broaden our search for valuable genetics. The goal of geneticists is described as resistance to FHB, but it is understood that there are also many genetic traits that reduce economic damage without reducing fungal growth. These should properly be identified as tolerance and escape traits, and they can help us reach the end result faster."

- Dr. André Comeau, research scientist, Agriculture and Agri-Food Canada, Sainte-Foy.

Reaching the payoff stage

"The development of resistance to FHB in spring wheat has been a slow process. For breeders, the challenge has been to introgress the multiple genes for resistance into regionally adapted cultivars that offer competitive agronomic and disease characteristics, within the confines of end-use quality and kernel visual distinguishability that define most of Canada's commercial production. In Western Canada, FHB-resistant lines are now entering the registration system and can be expected with increasing frequency. The yield penalty of obtaining FHB resistance has been overcome. However, work is required in regaining appropriate levels of resistance for the traditional diseases such as leaf rust."

Planning an escape

"Durum wheat is known to have greater susceptibility to Fusarium Head Blight and less resistance is available in the germplasm compared to common wheat. But the good news is the main durum growing area has escaped severe Fusarium damage. Our hope is that the existing variation in FHB resistance within durum may be enough for us to work with to sufficiently reduce damage under the relatively light and sporadic disease pressure experienced in the major Canadian durum production area."

- Dr. John Clarke, wheat breeder, Agriculture and Agri-Food Canada, Swift Current.

Turning the tide

"The total contribution of winter wheat to the Canadian agri-economy is well over $1.5 billion, but the continued onslaught of FHB in recent years stands to nullify all previous gains. Fortunately, we're seeing a lot of progress with resistant varieties that will help turn the trend back in our favour. In Eastern Canada, the first soft red Fusarium resistant winter wheat cultivar was registered in 2002 and two resistant soft white winter wheat lines were recommended for registration in 2003. In addition, the new Fusarium-resistant hard red cultivar, AC Morley, has gained widespread adoption by producers. The process to incorporate these sources of FHB resistance into cultivars for Western Canada is well underway."

Protecting livestock production

"The westward migration of the incidence of Fusarium-infected grains, from Manitoba through to Alberta, poses significant challenges to the expanding livestock sector, particularly swine. New data suggests current guidelines for deoxynivalenol (DON) are in need of re-evaluation, and that there may be an opportunity for pork producers to increase their utilization of DON-contaminated grains. However, greater assurances are required by regulators and the feed industry to do this. As we address the DON issue in wheat and barley, we must also be mindful of the increasing acreage of other grains, including grain corn, and the potential for new mycotoxin concerns."

Changing the production landscape

"We farm right in the heart of the Red River Valley. Before Fusarium, we grew a lot of wheat, and it wasn't uncommon in those days to grow three cereal crops in a row and one broad leaf crop. Today, Fusarium has hit us hard - if we're lucky, we only get a five to 10 percent infection, and in several years it's been much worse than that. Our quality has suffered and we've lost some of our income. Today, there's only two or three wheat varieties that we play around with now. We don't grow barley. We're into more risky crops, which isn't all positive. We've really pushed alternative income options - looking for ways to pull out a personal living that doesn't include the grain farm. It's all due to a lack of confidence in grain, and that's largely due to Fusarium."

Steady progress toward long-term success

"Although improving FHB resistance in barley will be a long-term effort, good progress has been made. A large number of lines have been screened for Fusarium resistance, and information on the FHB resistance of current barley cultivars has been provided to producers through provincial seed guides, to allow them to make informed decisions. The screening effort has also given barley breeders a better idea of the FHB resistance of their cultivars, so that they can plan their breeding efforts accordingly. All barley breeding programs in Western Canada have at least some lines with moderate resistance to FHB surpassing AC Metcalfe or CDC Sisler. A number of additional lines have been identified with promising FHB resistance, but further testing will be needed to confirm the results and determine their suitability."

Optimism from molecular genetics

"Fusarium Head Blight is the most important wheat disease challenge today and unfortunately, the inheritance of resistance is genetically complex. Resistance to FHB is complex because multiple genes are required, there are likely gene-to-gene interactions, genetic background influences resistance gene expression and there is environmental influence on gene expression. However, in spite of these complications, the new genetic studies and molecular breeding tools we have now bring a high degree of optimism that marketable Canadian wheat will be produced with FHB resistance."

Boosting detection power

"Lower guidelines for DON in wheat are imminent, and we need stronger detection method to meet these guidelines. Fortunately, there are a variety of new technologies emerging that provide some good options. One size may not fit all. Ultimately, the choice of method will be largely determined by the DON guidelines set in Canada and in markets abroad, and the needs of each sector of the grain industry."

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