Researchers from Aarhus University are playing a key role in the work to combat the destructive fungal disease wheat leaf rust, which poses a threat to global food security

The global supply of wheat will be under threat unless effective action is taken at international level. The name of the threat is wheat leaf rust, which is an umbrella term for three destructive and extremely contagious fungal diseases: yellow rust, black rust and brown rust. It attacks the leaves and stems of the grain plants and seriously affects the harvest yield. Evidence of the destructive effect has been seen in China, for example, where yellow rust attacks over the past three years have resulted in annual losses of between two and six million tons of wheat. In the United States, annual losses attributable to wheat leaf rust in recent years have amounted to more than one million tons. As wheat – together with rice – is the most cultivated grain worldwide, the disease is having a major impact on global food supply.

So says Professor MSO Mogens Støvring Hovmøller from the Department of Agroecology at Aarhus University. Together with other researchers from the University, Professor Hovmøller is playing a leading role in the work to combat wheat leaf rust.  This is because Aarhus University is home to the Global Rust Reference Centre (GRRC), which is running a variety of research and monitoring activities intended to boost global initiatives to deal with wheat leaf rust – particularly in developing countries.

New and aggressive fungal disease

For decades, wheat leaf rust has been held in check by targeted plant breeding, which has progressively helped develop resistant types of wheat. However, the situation changed in 1999.

“This was the year when a new variant of wheat leaf rust, designated Ug99, appeared in Africa. It is a strain to which most of the commercial wheat types have no resistance, which means that a large proportion of the global wheat types are under threat of attack,” says Mogens Støvring Hovmøller.

Since then, additional new strains of wheat leaf rust have appeared, particularly yellow rust. In recent years, this infection has spread to major wheat-producing regions in the United States, Australia, China, Africa, the Middle East and Asia.

“The spread of aggressive yellow rust may prove to be the fastest and most comprehensive spread of a damaging plant disease in history,” says Mogens Støvring Hovmøller.

“And new aggressive types of the fungal disease are developing all the time. What is more, these new strains are resistant to constantly increasing temperatures, which is bad news in a world that is experiencing global warming.”

Global reference centre in Flakkebjerg

In other words, a wide-ranging international effort is required to combat wheat leaf rust.

“If we are to prevent serious losses to the wheat harvest, we need co-ordinated input from the countries involved to implement solutions with the capacity to help right here and right now. At the same time, the international community needs to ramp up its efforts in the fields of research, plant breeding and monitoring,” emphasises Mogens Støvring Hovmøller.

At Aarhus University, the first steps towards an international working relationship to combat yellow rust were taken in 2009 with the establishment of the Global Rust Reference Centre (GRRC) at AU Flakkebjerg, which is located near Slagelse in Denmark. The centre was founded on the initiative of, and with financial support from, CIMMYT and ICARDA – two international organisations with global responsibility for developing new strains of wheat in the developing world.

“The centre stores and categorises fungal spores it receives from all parts of the world. We then test the spores on different types of wheat and in laboratories, including the DNA laboratory,” explains Mogens Støvring Hovmøller.

“Our aim is to improve the opportunities for preventing and forecasting new rust attacks. In addition, we are working to develop types of wheat that are resistant to new and aggressive strains of wheat leaf rust.

“Until the centre was established, the problem was that trial conditions varied around the world, and that the tests and trials were often performed by people with different levels of education and from different backgrounds. Naturally, this produced ambiguous results – which is a major problem if you are attempting to chart infection routes and spread patterns across national borders,” says Mogens Støvring Hovmøller.

Hope for future food supply

The reference centre is not the only contribution AU is making to combating wheat leaf rust. In a new research project under the leadership of Aarhus University, a number of universities and institutions in Denmark and abroad are working to determine how and under which conditions the rust fungus becomes more aggressive.

Researchers are attempting to build up an overview of the genetic codes in the fungus – known as effectors – that have a decisive effect on the ability of the fungus to adapt to new types of wheat. The results from the project will be entered into a database-powered and Internet-based system that researchers at the Department of Agroecology are developing for the UN Food and Agriculture Organisation (FAO).

“The battle to beat wheat leaf rust will be a long, tough campaign; there are no quick fixes. However, we are confident. We have access to a wide variety of wheat types that represent a comprehensive collection of genetic resources, and we have a unique team of international partners, researchers, plant breeders and computer specialists,” says Mogens Støvring Hovmøller, who hopes that research can contribute to securing the global food supply of the future.