Pigeonpea in the mix as search begins for more heat tolerant crops

The weather might be warming, but the world still needs to eat. Australians are among those searching for answers to crops that can beat the heat and still produce food that is both palatable and profitable.

Director of the Agrifood Innovation Institute (AFII) at the Australian National University (ANU), Professor Owen Atkin, says higher temperatures are impacting major crops across the world.

“There’s lots of data that is showing yields of rice and yields of wheat falling away as temperatures exceed their growth optimum,” Atkin says.

“In India, in Southeast Asia, rice yields fall once you have daily average temperatures exceeding the low 20s – particularly the night temperatures.

“It seems to be a night-time warming in that case, and a similar thing for wheat as well. And we’re moving into that warmer environment where we’re essentially seeing declines in yields with warm years.

“It’s a global phenomenon.”

The Grains Research and Development Corporation (GRDC) and ANU have just announced a three-year $1.9 million project to accelerate the development of heat-tolerant wheat genetics and to help identify what it is that makes a wheat crop able to survive, grow and continue to produce under high-temperature conditions.

Wheat is one of Australia’s biggest crops, with more than 36 million tonnes produced in 2022-23.

The research is being undertaken by ANU in partnership with the University of Sydney, University of New England, University of Western Australia, InterGrain and overseas partners.

Atkin says the global increase in heat waves is cause for concern.

“Every one-degree increase in global mean temperature is predicted to result in a six to 10 per cent decrease in wheat yields,” he says. “This is extremely concerning given the pressing need to increase crop productivity in line with a growing global population.”

Atkin says researchers know different genetic lines of wheat have different degrees of heat tolerance, but don’t really know why.

The University of Sydney, working with GRDC and Australian cereal breeders InterGrain, will look at identifying molecular markers for heat-tolerant traits to help make more heat-resistant varieties available to farmers.

The research will survey heat tolerance of wheat lines across three growing seasons.

“We are looking at the extent to which the heat performance in the field is aligned with physiological traits that we know underpin metabolic heat tolerance,” Atkin says.

“And what we’ve brought to this project are some techniques that enable us, I think pretty much for the first time, to screen hundreds of lines of wheat for variation in key traits that underpin your ability to acquire carbon out of the atmosphere and then use that carbon for building your biomass.”

What happens when wheat meets heat?

What we do know, according to GRDC genetic technologies manager Prameela Vanambathina, is that when it gets hotter, wheat develops earlier, with smaller flowers.

The plant’s efficiency in the process of photosynthesis stunts its growth and means a smaller yield.

Atkin says the answer could lie in the earliest days of growing.

“What we need to do is get the vegetative growth phase of the plant pre-flowering to be more robust, to be able to better cope with heat and continue to accumulate resources, carbon, and biomass so that the plant is actually bigger when it begins to flower,” he says.

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Fabaceae or Leguminosae – Pigeon pea (Cajanus cajani). Illustration. (Photo by DeAgostini/Getty Images)

“And that’s going to be underpinned by some of the work we’re doing, hopefully, which would be around how to improve photosynthetic performance and how to minimise respiratory carbon loss from the plant during that period of building up biomass in the crop pre-flowering.”

Vanambathina says it is also crucial to study the flowering stage of the plant.

“Pollen is extremely heat-sensitive, so the whole flowering stage, the reproductive stage, is one of the most crucial parts. And if you have a heat wave at the wrong time of a crop development, you can wipe out an enormous percentage of your yields as a result.”

Advancing sustainable agriculture with legume crops

The project could have applications beyond Australian wheat crops.

Atkin says the findings from how heat affects the ability of a plant to photosynthetically take carbon from the air could provide insights into carbon uptake in other crops and other ecosystems, from forests to grasslands.

“Our work is going to explore one of the key elements of that, and that is how is it the protein – the enzyme that does that carbon fixation – stop operating as well under hot conditions,” he says.

Other work on heat-resistant crops

GRDC is also partnering with the Queensland Department of Agriculture and Fisheries (DAF) and the Woods Group to look at the potential for another crop that knows how to beat the heat – pigeonpea – as a new broadacre summer pulse crop in Queensland and northern New South Wales.

Pigeonpea is one of the world’s most popular pulses, and is used to make the Indian dish toor dal.

GRDC grower relations manager Rebecca Raymond says the project builds on previous research that found pigeonpea had potential beyond its current role as a trap or refuge crop for cotton.

“Through consultation via GRDC’s National Grower Network, we know that the northern grains industry needs a robust summer pulse that is easier to manage and more adaptable than current options, particularly for the drier and hotter regions of south-west Queensland and north-west New South Wales,” Raymond says.

“However, we need to do a bit more work to establish a pathway to production success and everything needed for a sustainable pigeonpea industry in the region, so we’ve partnered on these investments to do exactly that.”

Raymond says the work will look at pigeonpea varieties that are different to those already used in Australia, with genetics sourced from the International Crops Research Institute for the Semi Arid Tropics (ICRISAT) and the Australian Genebank.

They are expected to be tougher and better able to withstand hotter and drier conditions than mungbeans and soybeans. Woods Group is looking at the development of an agronomic package to set farmers up for success with pigeonpea.

“Pigeonpea presents an exciting opportunity for Australian farmers,” Woods Group director Angus Woods says.

“Our aim is to ensure that as we build this industry, growers have the necessary support and information to succeed, especially considering the significant market potential in the Indian subcontinent, where pigeonpea is a staple.”

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