Fusarium head blight is a fungal infection most commonly found in wheat but it can also affect barley, oats, rye and other grains.

Dr. Anita Brûlé-Babel, a plant geneticist and wheat breeder with the University of Manitoba’s department of plant science explains, fusarium attacks the head of the wheat plant and the developing seed. “Basically it attacks the wheat by sending fungal spores up onto the head and infecting into the florets where the seed is developing. That’s where the infection begins and it spreads through the head as the infection progresses.”

Unfavorable Weather Supports Fusarium Development

Climatic conditions throughout Manitoba this year were ideal for the development of disease resulting in widespread infection of the province’s hard red spring wheat crop.

“We usually need a combination of things,” says Dr. Brûlé-Babel. “The inoculum has to be present in the field, we need susceptible varieties and we need the correct environmental factors.”

She notes that because the fungus is consistently present in fields in Manitoba, extending into southeastern Saskatchewan, and because most of the varieties grown in western Canada are susceptible, weather conditions are the variable that will determine the level of risk for development of the disease from year to year.

“Usually hot humid conditions are the most conducive to infection of the wheat plants by the fungus,” she says.

Southern Manitoba Southeastern Saskatchewan Face Greatest Risk

“If you look at the distribution of fusarium head blight and who’s likely to have conditions that are most conducive to fusarium, we definitely see southern Manitoba and southeastern Saskatchewan as the main areas, largely because we seem to be in a wetter climate so we have more humidity and we also tend to be warmer. As you move west and north conditions, either temperature or humidity, become limiting.”

Disease Affects Grain Yield and Quality

“Under heavy epidemics we see significant yield penalties as a result of heavy infections,” Dr. Brûlé-Babel notes. “But probably the more concerning fact is that this organism produces a toxin in the seed and that toxin essentially limits the utility of the grain. It becomes unsuitable for human consumption and unsuitable for certain animals. It degrades the quality and value of that crop and limits what we can do with it.”

Swine Especially Susceptible to Fusarium

“The species that can not tolerate very high levels of deoxynivalenon or fusarium are pigs,” says Manitoba Agriculture Food and Rural Initiatives (MAFRI) farm production extension specialist-swine Ron Bazylo based in Dauphin.

“It’s been shown that levels above one part per million in a complete feed will result in some feed refusal. If you have levels anywhere from one to two parts per million you’ll get feed refusal of up to five percent and at levels such as four parts per million you can get feed refusal of up to 25 percent.”

Bazylo notes he is aware of one producer who was feeding levels just above five parts per million and the pigs stopped eating completely. Although the mycotoxin doesn't appear to have a strong reproductive effect he recommends against feeding contaminated grain to dry or lactating sows.

He adds reports indicate Manitoba’s hard red spring wheat crops have be hit hard and he’s heard of levels of 15 to 16 parts per million of DON this year.

Species other than Swine Tolerate Higher Levels

“The guidelines from Agriculture Canada for growing beef cattle and sheep, for instance, indicate levels can go up to five parts per million. Affected grain has been fed to pregnant cows and ewes at levels up to ten parts per million without any affects on reproduction performance. Although the guidelines for dairy cattle and horses are one part per million, identical to swine, that’s probably as a result of less research done on these species on the effects of the mycotoxin.”

Scientists Strive to Improve Wheat's Genetic Resistance to Fusarium

Scientists are attempting to improve the ability of wheat cultivars to withstand the fungus.

“The challenge from the scientific point of view is to incorporate genetic resistance to this pathogen. That's the long term goal,” says Dr. Brûlé-Babel. She notes, “The sources of genetic resistance that we have individually are not 100 percent. They will reduce the level of infection but they don’t eliminate it and so the challenge is to really try and put combinations of resistance together.”

That is the goal of a research project being undertaken by Anthony (Tyler) Guerrieri, a graduate student with the University of Manitoba’s department of plant science. The project, one of four graduate student projects being supported through the Canadian Wheat Board’s (CWB) 2008 CWB fellowship awards, will examine the interaction between the fusarium pathogen and specific host resistance.

“What we intend to accomplish is to find new resistance genes in wheat to fusarium head blight or also possibly characterize previously existing genes for which the mechanism is unknown,” Guerrieri explains. “We know that there are a number of different resistance genes, each contributing to the total resistance of a wheat cultivar.”

No Single Gene Offers Total Resistance

“There are no genes that we know of which give total resistance,” he points out. “They each contribute a small amount and the higher the number of genes that a wheat line or variety has the greater its total resistance.”

The work will be conducted primarily in the university’s greenhouse and in the laboratory and will look at two variants of the toxin produced by the fusarium fungus; 15-A DON and 3-A DON, and their relationship with the resistance genes in wheat.

Guerrieri notes, “Epidemiologists and pathologists have been observing, in our region, that there’s a shift to this 3-A DON which is more toxic both to plants and animals.”

He concedes transferring resistance from a line that may be very resistant but lacking in agronomic or end use characteristics to a line that has the desired agronomic traits and is acclimatized to our region but is not very resistant is complex. However he expects to complete his portion of the project within two years, the average length of a masters program in the department of plant science.

Guerrieri is hopeful his research will make a meaningful contribution to the university’s fusarium resistance program and ultimately result in the release of more resistant wheat varieties.

“It may be used by plant breeders when they are evaluating the merits of experimental wheat lines for use in a breeding program. The information may also be used indirectly in any number of fields including pathology, epidemiology, toxicology.”

Swine Producers Advised to Avoid Infected Grain

Meanwhile Bazylo encourages swine producers, if they’re purchasing grain, to make sure it comes from a producer that has had it tested for fusarium. And, if they’re feeding their own grain, to collect representative samples from the fields for testing.

He notes there are two laboratories in Manitoba that will check for DON levels, the Canadian Grain Commission and Central Testing Laboratories, both based in Winnipeg.