Wheat, 1; Stem rust 0: blockbuster gene could be kryptonite for costly fungus

An international team of researchers have found a gene that could make wheat crops immune to stem rust – a fungus which has plagued wheat for millennia.

The researchers located the gene in a little-known wild species of grass: the wild goat grass, or Aegilops sharonensis. When this gene was transplanted to a susceptible plant, it became resistant to every form of stem rust fungus the researchers tested.

“We now have this blockbuster gene that confers amazing immunity,” says Dr Brande Wulff, a wheat researcher now at King Abdullah University of Science and Technology (KAUST), Saudi Arabia, who carried out some of the research at the John Innes Centre, UK.

“If I were stem rust, I would be shaking in my spore.”

Wulff is a co-author on a paper in Nature Communications describing the gene and its effects when transferred to other plants.

“We have yet to come across an isolate of the pathogen which can overcome the gene,” adds first author Dr Guotai Yu, also a researcher at the John Innes Centre.

The gene itself, called Sr62, codes for a substance called a tandem protein kinase. It’s not clear exactly how this protein helps to deflect stem rust – researchers are now investigating this so that they can improve its mechanism.

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Aegilops sharonensis has long been known as a hardy and fungus-resistant grass. But it’s a difficult grass to cross-cultivate with wheat, and it has a fairly small wild habitat, meaning it’s been mostly overlooked by previous wheat breeders.

“Given the great difficulties in crossing Aegilops sharonensis to wheat, we were fairly certain that the rust resistance genes discovered in the wild species would be novel,” says co-author Professor Brian Steffenson, from the University of Minnesota, US.

The researchers are now planning to breed some common wheat varieties genetically modified to include Sr62 among a suite of other genes.

“Pathogens like stem rust already reduce the yield of wheat by 21 per cent. Not only is the grain itself lost or damaged by the pathogen, but also the energy that goes into its production: an equivalent of 420 billion kilowatts – enough to power 300 million homes in the developing world – is wasted,” says Wulff.

“If we can intervene with genetics, by recruiting the resistance found in this wild, wispy-looking grass then that would be an amazing contribution to agriculture and climate change.”

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