New wheat varieties needed to feed Australia in a warming world

New wheat varieties, which can be sown deeper to protect them from heat and drought stress, could increase wheat yield in Australia by 18–20% according to a new study from CSIRO.

The authors of the new study used modelling and field data to assess the ability of newer wheat varietals under the climate conditions of the past 120 years.

Wheat is the third-largest grain crop in the world, the authors say, supplying around 20% of the world’s total calorific and protein intake. 

The research team found that certain newer varieties of wheat, armed with gibberellic-acid-sensitive (GAS) dwarfing genes, can be sown deeper and earlier – deeper to provide critical access to underground water stores, and earlier to reduce the impacts of drought and heat-waves in the warmer months.

But why do these dwarfing genes help? To understand that, we need to dive back into the history books.

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The father of the Green Revolution

Part of the reason wheat is so central to the human diet is because around 99% of the crop nowadays is ‘semi-dwarf’, a varietal developed in Mexico in the mid-1940s–50s by Norman Borlaug as a way to increase wheat yields. Semi-dwarf wheat is less prone to bending and collapse, it takes less time to grow to the height needed to harvest grain, and it’s more responsive to fertilisers.

The success of this kind of selective breeding swept the world, with high-yielding wheat becoming a staple global crop, meanwhile more innovative breeding methods were being developed for all sorts of other crops, ultimately culminating in the Green Revolution – a movement credited with saving perhaps a billion people from starvation.

But as temperatures rise and rainfall becomes more variable across Australia, it’s predicted that wheat production here could collapse, because the traditional semi-dwarf plant is vulnerable to excesses of heat. That’s because, when sown deep, it emerges later and sparser, delaying flowering and the growth of the grain until the hotter months, when grain yields are reduced.

GAS dwarfing genes, on the other hand, are an alternative dwarfing gene to the type bred into the plant by Borlaug, and they can circumvent some of these tricky problems: they have what’s called ‘early vigour’ in comparison with older semi-dwarf varietals – they can produce greater yields when sown earlier in the year and grown for less time. They can also be buried deeper and still emerge with a strong yield.

This is good news, because the alarm bells for Aussie wheat are already being rung. In February, a team of researchers at the University of Sydney published new research that warned that many common varieties would not withstand the ravages of climate change.

The team ‘stress-tested’ 23 varieties of wheat at an atmospheric CO₂ level of 800 parts per million (double the current concentration), and at temperatures of 35°C. They found that some of our most popular plants cannot withstand the interacting effects of both elevated CO₂, which closes the wheat’s stomata leading to higher leaf temperatures, and higher atmospheric temperature, which can shrivel the grain kernels and force the production of less viable pollen.