Wheat at Risk: Researchers are Tackling the Growing Threat of Tan Spot

Wheat fields stretching across the Prairies are among the most iconic landscapes in Canada. As the country’s largest field crop, wheat plays a critical role in both the national economy and global food supply, with around 30 million tonnes harvested annually—far more than Canadians consume, making it a key export to countries worldwide.

However, this vital crop is under threat from a growing menace: tan spot disease, a fungal infection that has emerged as one of the most destructive diseases affecting wheat crops globally. Researchers in Canada, who have a long history of studying wheat dating back to the late 1800s, are now at the forefront of efforts to combat this disease.

The Growing Threat of Tan Spot Disease
Tan spot disease, caused by the fungus Pyrenophora tritici-repentis, was first identified about 50 years ago and has since spread worldwide, becoming a significant threat to wheat production. The disease manifests as tan-colored lesions on the leaves of infected wheat plants, which can severely impair the plant’s ability to photosynthesize, stunt growth, and drastically reduce yield and grain quality. In severe cases, tan spot can reduce wheat yields by as much as 60% and lead to red smudge, a discoloration of the grain that diminishes its market value.

The fungus thrives in wet conditions, and with spring rains creating ideal conditions for infection, the disease is a persistent challenge for farmers. While fungicides are commonly used to manage the disease, the ongoing evolution of the pathogen necessitates continued research into more effective strategies and the development of resistant wheat varieties.

AAFC Researchers Lead the Fight
A team of researchers at Agriculture and Agri-Food Canada (AAFC) is spearheading a national and international collaboration to understand the global evolution of tan spot disease and develop strategies to curb its impact. Led by Dr. Reem Aboukhaddour at the Lethbridge Research and Development Centre, the team includes experts from across Canada and partners in Europe, North and South America, North Africa, India, Japan, and Australia.

The researchers are using advanced techniques in genomics, pathology, and bioinformatics to analyze the genetic makeup of the pathogen and track how disease-causing genes have evolved across different strains. By studying mutations, duplications, and transposons—”jumping genes” that can move within or between genomes—the team is uncovering the mechanisms behind the pathogen’s virulence and identifying new forms of the fungus that pose increased risks to wheat crops, including durum wheat in Canada.

“It’s so important to get a clear picture of how the pathogen that causes tan spot disease is evolving. This will help us spot trends, environmental conditions, and other factors that enable the disease to thrive, and hopefully discover solutions that help manage it effectively,” says Dr. Aboukhaddour.

While the research is ongoing, the AAFC team has already made significant contributions to the scientific community by providing fully sequenced genomic data of P. tritici-repentis from diverse global sources. This information is crucial for developing future solutions to reduce the incidence of tan spot disease and protect wheat crops from this severe economic threat.