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Staying ahead of fusarium head blight on oat

Never say never. Even though oat is much less affected by fusarium head blight (FHB) than crops like wheat or barley, researchers are doing their best to stay one step ahead of the disease by breeding for FHB resistance. For many years, people thought FHB was not a problem in oat in western Canada likely because the symptoms are difficult to see on the growing crop. However, laboratory tests conducted as part of recent research and monitoring efforts have shown that FHB does occur on oat in Manitoba and Eastern Saskatchewan. “Even though oats do not visibly show very much at all in the way of symptoms from fusarium, the fusarium is actually on the plants in the field. It’s at much lower levels than in wheat and barley,” explains Dr. Brian Rossnagel. He directs the barley and oat breeding programs at the Crop Development Centre in Saskatoon, which is funded by Saskatchewan Agriculture and the University of Saskatchewan.

Oat is much less affected by fusarium head blight than wheat or barley, and although it has not caused economic concern for Prairie growers, breeders hope to keep it that way. Photo by Bruce Barker

Rossnagel is leading a new two-year project to investigate the genetics of FHB resistance in oat. It involves research on key components in the process to develop FHB-resistant varieties. “There isn’t a problem at the moment with fusarium in oat but there always is potential and we have an opportunity to make sure that potential never realizes itself. Because oats are directly used as a food product, we want to make absolutely certain that there are no issues,” he emphasizes. “All of the food manufacturers that utilize oat continually monitor the products coming in for toxins and none have found the toxins on the groats,” notes Rossnagel. He says FHB can occur on the oat hull, but people eat the groats, the dehulled grains, and dehulling removes the fusarium and fusarium toxins.

He explains that FHB in oat could become a problem in the future if conditions change. “All fusarium species like warm, moist conditions. If the climate is truly changing and areas of the Eastern Prairie region of Western Canada become consistently wetter and warmer, then we may see more fusarium on all crops.”

Oat breeders want to be ahead of any FHB problem because breeding new crop varieties can take a decade or more, especially when breeding for resistance to a complex disease like FHB, which has been a challenge for wheat and barley breeders for many years.

One of the complexities is that FHB can be caused by more than one species of fusarium. Research by Dr. Andy Tekauz of Agriculture and Agri-Food Canada (AAFC) and others has found that FHB in oat on the Canadian Prairies is caused primarily by Fusarium graminearum, F. poae, F. sporotrichioides and F. avenaceum, with the proportions of each species changing from year to year.

Rossnagel says, “In wheat and barley, the major concern is with Fusarium graminearum, which produces the toxin we refer to as DON, deoxynivalenol. DON is a very serious neurotoxin if it’s there in large enough quantities, and it is a problem in feeding livestock, particularly pigs. In oat, we find most of the fusarium is not Fusarium graminearum but a couple of other very common species: Fusarium poae and Fusarium sporotrichioides. Those two don’t lead to much DON toxin, but they can sometimes lead to the development of other toxins which can be as much or even more concerning than DON.”

Rossnagel’s project, which is funded by the Western Grains Research Foundation (WGRF), is one of the outcomes out of an earlier WGRF project led by Tekauz. That project included a comparison of the response of various oat lines to Fusarium. One of the Crop Development Centre’s breeding lines, called OT 3028, had consistently better tolerance to Fusarium and much lower levels of DON than most other oat lines in independent tests at AAFC’s research centres at both Winnipeg and Ottawa.

The new project will focus on the heritability of FHB tolerance/resistance using the OT 3028 genetic material. “The main cross we will be working with is a cross between that Crop Development Centre line and a variety from the US called Robust, which is exceptionally susceptible to Fusarium,” explains Rossnagel. “Crossing those two lines allows us to produce a large population of segregating sister lines, some of which will carry the tolerance/resistance and some of which won’t. That’s how we can evaluate the genetics behind the tolerance/resistance that is in OT 3028.”

The researchers hope to develop some molecular markers for the genes associated with resistance to fusarium. Those markers could be used by oat breeders anywhere in the world to screen breeding material for fusarium tolerance without having to infect the material with the fungus, making the breeding process more efficient. “If we get really lucky, we’ll find one major resistance gene and we’ll find molecular markers that are very closely associated with that resistance gene, so a breeder then could use the marker to eliminate the susceptible lines. However, based on results to date with both barley and wheat, it would be shocking to find it was that simple,” says Rossnagel.

Previous research indicates fusarium resistance is much more likely to be due to several genes rather than one single gene. He says, “What we hope we’ll find is a few major areas of the genome that are conferring the resistance. Then we can select for those using molecular markers and then go on using just the breeding lines that carry those regions of the genome while conducting the rest of the breeding work to find the best lines.”

Rossnagel’s team will also evaluate the variability of FHB resistance/susceptibility in a wide array of oat germplasm from Canada and other countries. He adds, “We’re also sending our materials to Scandinavia where fusarium is an even bigger problem and is actually a problem on oat there. They have considerably higher levels of infestation than we do because their conditions are just perfect for fusarium most years. They’ve even got a couple of fusarium species that fortunately we don’t have here that are even nastier than the ones we have.”

An oat plant with resistance to one fusarium species does not necessarily have resistance to other fusarium species. So the researchers are conducting a survey of FHB prevalence and severity in Saskatchewan oat fields that includes identification of the fusarium species. The survey results will help them decide which particular fusarium species to use when searching for resistance in the oat lines.

In addition, the researchers will be developing PCR (polymerase chain reaction) techniques to detect, identify and quantify the fusarium species. Rossnagel says that will allow more efficient detection of the species present and hopefully eventually the quantification of the amount of FHB present on plant and grain samples, which could help plant breeders avoid the costly
and time-consuming step of toxin determination.

Rossnagel concludes, “There’s no concern for oat growers, end-users or consumers at this time. To be honest, I would hope that the results of this research are positive, but that they never have to be used!”