Researchers have successfully identified and isolated the first rust pathogen gene that wheat plants detect and use to activate their own in-built disease resistance. The gene was found against stem rust, a disease that has not been a problem here for many years but is known to be making a comeback and has appeared again in Sweden.

This research means that it is now possible to test the DNA of a wheat variety anywhere in the world to check if rust can overcome the plant’s own rust-resistance gene, called Sr50, which has been introduced into high-yielding wheat varieties.

Oats, wheat and barley

While growers in this part of the world are most used to dealing with crown rust in oats, yellow rust and brown rust are less common but still deadly problems in wheat and barley. Black stem rust has been making a comeback in Europe in recent years and it remains a devastating problem in other parts of the world such as east Africa, Australia, the Middle East, Asia and the US.

The discovery of this gene was made using new technologies, including whole-genome sequencing, which decodes DNA, and computer bioinformatics, which allows vast amounts of sequence data to be analysed.

The research was conducted by groups from Australia, CSIRO, Rothamsted Research, the University of Minnesota and the USDA.

Spraying and selection

In the short term, this technique could be used to indicate whether a wheat variety needs to be sprayed with fungicide to protect it against stem rust. In the longer term, this information can be used to help prioritise resistance genes for further development, now that the process of resistance development to Sr50 is understood to occur via mutation of a gene called AvrSr50.

The findings are also likely to lead to a better understanding of how rust pathogens infect wheat, evade detection by the plant and ultimately cause yield losses.

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