The foundation for cereal crops that beat the heat

A project conducted by University of Adelaide and Macquarie University researchers has revealed insights into how an Australian ‘wild rice’ thrives in extreme heat, opening the door for the breeding of new cereal crops that can withstand high temperatures.

Cereal crops like rice and wheat are a major source of nutrition for billions of people, but demand is increasing faster than yields worldwide. As global temperatures rise and extreme heatwaves become more common, new crops that can survive extreme temperatures will be essential for food security.

Luckily, Australia has a rich selection of ‘extremophile’ crops that we can study to learn their survival secrets. One of these is Oryza australiensis, a wild rice that is native across northern Australia and grows vigorously at temperatures up to 45°C.

Over the last few years, Aaron Phillips, a food science PhD student at the University of Adelaide, artificially simulated the heatwaves of Australia’s savannah and painstakingly compared the wild rice to commercial rice to understand how it survives in extreme temperatures. This work was supported by Professor Brian Atwell from Macquarie University, and ANU colleague Dr Andrew Scarfaro.

The team confirmed that while the growth of the commercial rice suffered once temperatures rose above 35°C, the wild rice thrived at 45°C.

While comparing the two plants, the researchers determined that wild rice was able to undergo photosynthesis more efficiently than the commercial rice at 45°C, and that this contributed to its enhanced growth.

Photosynthesis is the process by which plants capture carbon dioxide from the atmosphere and convert it into carbohydrates for growth and energy production. It is a highly complex process with many different steps, each catalysed by a different enzyme.

One particularly thermostable, or heat-resistant, photosynthesis enzyme was found to be behind the increased efficiency of the process in wild rice. The researchers found that the levels of this ‘wild’ variant, along with its enhanced stability under hot conditions, allowed the wild rice to remain functional even as temperatures soared.

The findings of their research were published in the journal Plant Molecular Biology.

What’s next?

Importantly, the thermostable photosynthesis enzyme is only one part of the heat-resistance puzzle.

To help discover new pieces of this puzzle, the University of Adelaide and Macquarie University team, together with ANU collaborators, has sequenced the entire genetic code of the wild rice.

Researchers worldwide can now use this resource to describe new genes, or new variants of known genes, that control how the plants tolerate extreme environments.

This paves the way for new research into ‘engineering’ super-efficient crops that can tolerate not only extreme temperatures, but also drought, excess salt and low nutrient availability, all with the goal of establishing hardy new crops around the world.