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 over 2,000 years.
The stem rust pathogen Puccinia graminis is capable of completely destroying 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 once again the disease threatens harvests.
Resistance genes
Scientists have now developed a new wheat variety that show exceptional resistance to stem rust.
The team – led by Led by Dr Mick Ayliffe at the Canberra laboratories of Australia’s national science agency CSIRO and including researchers from the University of Minnesota, Aarhus University, The John Innes Centre in the UK, USDA and Xinjiang University – used genetic technologies to build and insert a ‘stack’ of five rust resistance genes into a single location in the genome of a common wheat variety.
In this new approach, individual resistance genes are assembled rapidly 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 over 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.
Study:
A five-transgene cassette confers broad-spectrum resistance to a fungal rust pathogen in wheat
Authors: Ming Luo, Liqiong Xie, Soma Chakraborty, et al.
Nat Biotechnol (2021)
doi.org/10.1038/s41587-020-00770-x
Dr Ayliffe’s research was supported The 2Blades Foundation’s continuing programme on the control of wheat diseases which was started in 2008. The Illinois-based 501(c)(3) charitable organisation is dedicated to the development of durable disease resistance in crops, in collaboration with leading research institutions around the world and at the 2Blades Group in The Sainsbury Laboratory, Norwich, UK.
