Fusarium Graminearum: A Population in Transition

 

The population of Fusarium graminearum, the fungus that can cause gibberella ear rot in corn and Fusarium head blight in small grain cereals, is changing in Canada. A potentially more toxigenic form of the fungus is increasingly being observed in Canadian crops.

There are three chemotypes of Fusarium graminearum around the world. They are distinguished from each other by the mycotoxins they produce. Traditionally, the main type in North America has been the form that produces both deoxynivalenol (DON) and 15-acetyldeoxynivalenol (ADON). The more recent form being detected is one that forms DON and 3-ADON. DON, also known as vomitoxin, is
a relatively mild toxin compared to other mycotoxins found in grains. In some animal species, such as hogs, it may cause reduced feed intake. Cattle are more tolerant of DON in their diet.

In 2004, the Grain Research Laboratory (GRL) at the CGC initiated a project with Dr’s. Ward and O’Donnell of the Agricultural Research Service (ARS) of the United States Department of Agriculture to study an historical collection of cultures of Fusarium graminearum from various cereal types collected in Canada. The research shows that the species in Canada maybe more complex than previously thought, and is in a state of flux.

Randy Clear, Program Manager, Microbiology, in the Grain Research Laboratory at the Canadian Grain Commission

To date, the GRL has collected Fusarium-damaged kernels (FDK) from grain samples submitted to the CGC for harvest surveys from 1984 to 2006, and collected FDK and cultures from organizations across Canada. The samples originated from Manitoba, Saskatchewan, Alberta, Ontario, Quebec, New Brunswick, Prince Edward Island and Nova Scotia.

Using the samples, the GRL prepared cultures of the fungus and sent them to the ARS. The ARS used their recently developed technology to determine the chemotype of the fungi based on genetics, while the GRL grew a select number on rice to measure the quantity of toxin produced in culture.

What is most striking about the new chemotype is that in the laboratory, it produced about twice the amount of DON as the chemotype population producing DON and 15 ADON.

The DON/3 ADON form has been found in Ontario corn as early as 1980, but there has been little to no change in the population, with about 5% of FDK in Ontario wheat in 2006 with the DON/3 ADON population.

That is far different than the results from grain samples from the rest of Canada.

In western Canada the population of the new chemotype increased significantly between 1998 and 2006. The greatest change was in Manitoba, where the population rose from about 5% to over 50% during that time.

In P.E.I., New Brunswick and Nova Scotia, over 90% of cultures from recently collected samples are comprised of the new chemotype. The population in Quebec is much less, at about 30%.

However, recent samples of infected Ontario corn provided by the CGC in Chatham, as well as from Albert Tenuta of the Ontario Ministry of Agriculture, Food and Rural Affairs and fungal cultures from Art Schaafsma and Lily Tamburic-Ilincic of the University of Guelph, have
demonstrated that the new chemotype is presently only a small part of the population affecting Ontario corn.

A manuscript on the collaborative project is being prepared for publication.

Studies like this are only part of the information gathered by annual crop surveys. For more information visit the CGC website at www.grainscanada.gc.ca. To participate in new crop surveys, contact the Ontario Corn Producers’ Association, Ontario Soybean Growers, Ontario Wheat Producers’ Marketing Board, Ontario Bean Producers' Marketing Board and/or Ontario Canola Growers Association.