FHB a Blight on Wheat

Wheat research faces a stark choice: Stop Fusarium head blight (FHB) or leave growers at risk. FHB is an ongoing issue for wheat farmers, leading to losses for Western Canada in the hundreds of millions of dollars in epidemic years such as 2016. The fungal disease affects the heads of small grains such as wheat, barley, and corn, and is especially damaging to durum wheat. Given the high stakes, and the challenging enemy involved, scientists are seeking to apply the latest technology to the battle with the project "Imaging for improving Fusarium-damaged kernels and deoxynivalenol resistance in Canadian wheat".

“The idea for this project came from several years of working on FHB and looking at Fusarium damaged kernels (FDKs),” said Dr. Samia Berraies, research scientists with Agriculture and Agri-Food Canada (AAFC) at the Swift Current Research and Development Centre, Swift Current, Saskatchewan.

“Through our program and working with wheat breeders, we have been seeking to improve the level of FHB resistance, especially in durum wheat which is particularly susceptible to the pathogen.”

To that end, researchers increased their efforts in examining the fallout from the disease post-harvest.

Deadly DON

“Fusarium has a huge impact on grading, as FDKs immediately degrade your load of grain,” said Dr. Berraies. “As well, those kernels are a reservoir of DON mycotoxin produced by the fungal pathogen fusarium graminearum that causes FHB.”

Deoxynivalenol (DON) is a poisonous compound that accumulates in the grain of cereal crops. While various livestock species react differently to this mycotoxin,, animals consuming high levels of DON may experience reduced feed intake, reduced immune response and reproductive dysfunction.

A key part of combatting FHB is scrutinizing the affected kernels, but that is no small feat.

“We assess thousands of samples, because the kernel infection level and severity of the damage varies widely among the breeding or genetic material. We usually conduct a visual assessment to rate FDKs in the harvested sample. This is a tremendous task, requiring good eyes and thorough knowledge to identify and separate the sound, healthy kernels from the damaged ones.”

Image is everything

In light of these challenges, researchers explored the concept of high throughput assessments. After reviewing the options, they concluded that imaging had the greatest potential to help inspect FDKs in a timely, consistent manner.

“When you are viewing 10 samples per day with just the naked eye, the tenth one is bound to be less precise than the first one. An image analyzer solves that problem, as long as it is properly calibrated [adjusted] for the task.”

Once the machine is calibrated to detect FDKs, it can analyze a sample in two minutes that required 45 minutes in the past. Putting it to work, scientists examined the degree of infection in damaged kernels, separating them into “heavily infected” and “less infected”. They will then relate this to the level of resistance offered by the durum line being sampled.

“We know that Fusarium is a very tough disease, particularly for durum, as the resistance is associated with several minor effect genes. Individually, these genes have a minimal impact on resistance, so we are trying to capture as many of them as possible and combine them to build greater resistance. We really want to dissect the FDK infection in the kernels and compile and fine-tune more genetic factors associated with FHB resistance.”

A package deal

Part of the challenge in breeding fusarium-resistant durum lines is that scientists must look at the entire package and ensure that a line has strong agronomics, as well as resistance to diseases other than FHB.

“A line might be resistant to FHB, yet it is tall and light and therefore does not serve the farmer. We need to bring together a number of desirable traits that growers require without compromising any one of them.”

As the team marshals it resources to combat FHB, they know it won’t be easy, but they recognize that progress is critical.

“In 2014 and 2016, durum wheat growers lost millions of dollars in revenue to FHB, and the harvest was not even fit for feed due to high levels of mycotoxins. This is why we continue to focus on resistance, and began breeding DT2009 in 2021, the first durum wheat variety in Canada and the world with intermediate resistance to FHB. Using technology like the image analyzer should allow us to develop even more resistant lines in the future, building on the success of DT2009.”

As these new varieties, go, so goes Canada’s position on the world stage as a leader in wheat production.

“The reputation of high-quality wheat that Canadian farmers offer is a distinction in international markets, making paramount the maintenance of our high standards for crop cleanliness and consistency. Deploying cultivars with improved resistance to FHB, FDK and DON offers the most effective approach for limiting the economic and ecological impacts of the disease.”

At the Swift Current Research and Development Centre, FDK and DON are top priority traits for the wheat breeding and pathology programs. Those two culprits are associated with end-use quality and food safety, two of the biggest concerns of Canadian wheat growers and the national and international food industry.

“Developing and using innovative technology in this project will contribute to strengthening Canada’s reputation as a supplier of top quality, healthy and safe wheat through an in-depth and more refined understanding of the genetic control of FDK and DON. Accelerating the genetic gain of FDK and DON resistance with high throughput imaging will preserve durum’s contribution to Canada’s international market share. Seed growers can also benefit from marketing lines that will present high FDK and DON resistance levels, while commercial farmers bring cultivars to the elevator that maximize grade, translating into higher returns.”

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