An international consortium of scientists has developed a hardy new wheat variety that is resistant to a particularly virulent fungal disease, which threatens global food security.

According to the study – partially funded by the 2Blades Foundation and published in Nature Biotechnology​ – stem rust is one of the world’s most devastating plant diseases, with records of stem rust pandemics dating back more than 2 000 years.

The stem rust pathogen, Puccinia graminis​, can destroy a crop of wheat in a matter of weeks.

The most effective and environmentally benign way to control wheat rust is through the use of genetic resistance, and a successful solution was developed by Norman Borlaug’s breakthrough Green Revolution in the 1960s.

However, rust pathogen races have subsequently evolved to overcome that resistance and the disease once again threatens harvests.

Resistance genes

Scientists have now developed a new wheat variety that shows exceptional resistance to stem rust.

The team – led by Dr Mick Ayliffe at the Canberra laboratories of Australia’s national science agency, the Commonwealth Scientific and Industrial Research Organisation (CSIRO), including researchers of the University of Minnesota, Aarhus University, The John Innes Centre in the United Kingdom, the United States Department of Agriculture (USDA), and Xinjiang University – used genetic technologies to build and insert a ‘stack’ of five rust-resistant genes into a single location in the genome of a common wheat variety.

With this new approach, individual resistance genes are rapidly assembled into a single stack and introduced into a chosen wheat line. This not only eliminates time-consuming breeding efforts, but also ensures the desirable trait (determined by multiple genes) will not be lost in subsequent breeding.

According to the authors, the result represents an advance in conventional wheat breeding methods, where the development of an equivalent disease-resistant wheat would require a long succession of crosses, and the resulting resistance could be lost in subsequent crosses.

While this particular study targeted wheat stem rust, the same technology is being used to create durable resistance for wheat stripe and leaf rust diseases that also attack wheat crops.

In future, gene stacks could be prepared with genome-editing tools to develop improved crops that may be considered non-genetically modified in some countries, such as the US.

Food security

The research could help address critical global food security challenges. Wheat provides roughly 20% of calories and protein for human nutrition worldwide and is the third largest crop grown in the US.

The most effective and environmentally sound way to defend against wheat rust diseases is through the deployment of resistance genes in wheat varieties. This is particularly important in developing countries where the fungicides used to combat rust disease may be expensive or unavailable.

International adoption of rust-resistant wheat varieties is essential, since rust fungi produce trillions of spores that can be carried by winds for thousands of miles – even across oceans – to infect vulnerable wheat crops. – Bakery and Snacks