Credit: CC0 Public Domain
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Credit: CC0 Public Domain
Australia's vital agricultural sector will be hit hard by steadily rising global temperatures. Our climate is already prone to droughts and floods. Climate change is expected to further accelerate this, causing sudden flash droughts, changes in rainfall patterns and severe flooding. Farm profits fell by 23% in the 20 years to 2020, and this trend is expected to continue.
If left unchecked, climate change will make it difficult to produce food on a large scale. We get more than 40% of our calories from just his three plants: wheat, rice, and corn. Climate change poses a very real risk to these plants, and recent studies suggest the possibility of simultaneous crop failure.
We have long modified crops to fight off pests or increase yields, but so far no commercial crops have been engineered to withstand heat. We are tackling this problem by enabling soybean plants to withstand hotter global weather extremes.
What threat does climate change pose to our food?
The Food and Agriculture Organization of the United Nations estimates that food production will have to increase by 60% by 2050 to feed the projected 9.8 billion people on Earth.
For every 1°C increase in temperature during the planting season, rice yields decrease by 10%. A 1 degree rise in temperature could reduce wheat yields by 6.4% worldwide. It's as if major crop exporters like Ukraine (6% of pre-war traded crops) were removed from the equation.
Plants, unlike animals, cannot escape heat. The only solution is to make them more tolerant of what is about to happen.
These events have already arrived. In April 2022, farmers in India's Punjab state lost more than half of their wheat crop due to a scorching heat wave. Scorching temperatures are wreaking havoc on crops in Southeast Asia this month.
What happens to plants when faced with extreme heat?
Plants use photosynthesis to convert sunlight and carbon dioxide into sugary food. If it's too hot, this process will be even more difficult.
As heat increases, plants evaporate water to cool themselves. If a plant loses too much water, its leaves will wither and growth will stop. When a plant's solar panels (leaves) wilt, they can no longer capture sunlight. Without water, we don't have the energy to produce the fruits and grains we want to eat. When the temperature reaches 50°C, photosynthesis stops.
Warmer temperatures make it harder for plants to produce pollen and seeds, which can cause them to bloom earlier. Heat weakens plants and makes them more susceptible to pests and diseases.
From rice to wheat to soybeans, our seed crops rely on sexual reproduction. To obtain a sufficient yield, plants must be fertilized (for example, pollinated by bees or flies).
If a heatwave hits during the fertilization period, plants have difficulty setting seeds, reducing farmers' yields. To make matters worse, high temperatures produce sterile pollen, which reduces the number of seeds a plant can produce. Pollinators such as bees are also having difficulty adapting to the heat.
Preparing the crop
To give our crops the best chance, we need to use genetically modified technology. Although these are often controversial, they are the best way to respond to threats.
This is because genetic modification allows for more precise control over a plant's genome than traditional methods of breeding for specific traits. It is also much faster because genes can be isolated from one organism and transferred to another without sexual reproduction. Therefore, although it is not possible to cross-breed sunflower and wheat using sexual reproduction, it is possible to obtain genes from sunflower and transfer them to wheat.
For decades, we have relied on genetically modified versions of some of our most important food and fiber crops. Almost 80% of the world's soybeans have been genetically modified to increase yield and make them more nutritious. Genetically modified canola accounts for more than 90% of production in Canada and the United States, and approximately 20% of canola grown in Australia is genetically modified. However, until now, crops improved to withstand heat have not been commercially adopted.
One way to do this is to look for heat-tolerant plants and pass that ability on to your crops. Some plants, such as the living fossil Welwitschia mirabilis, can survive in the Namibian desert, where rainfall is almost zero.
heat shock and heat sensor
Plant cells also have heat shock proteins, just like our cells. These help plants withstand heat by protecting the protein folding process of other proteins. In the absence of heat shock proteins, important proteins would be unfolded rather than folded into the shape appropriate for the job.
The function of these existing heat shock proteins can be enhanced to allow cells to continue functioning under higher temperature conditions.
It is also possible to fine-tune the behavior of genes that act as heat sensors. These genes act as master switches, controlling the cell's response to heat by summoning protective heat shock proteins and antioxidants.
In our laboratory, we modified soybean plants by enhancing this heat-sensing master switch gene. Soybean plants that expressed this gene at higher levels had significantly increased defenses. Under short and intense heatwave conditions, these modified plants wilted less, produced more viable pollen, had less structural deformation, and had improved yields even under heat stress conditions.
What about wheat?
Although we have become accustomed to genetically modified soybeans, we have not yet come to terms with the need to modify our most important staple crop, wheat.
Heatwaves cause similar problems for wheat, but they are not accepted by local communities. There is a strong backlash against genetically modified wheat.
In the lab, researchers at universities and agricultural companies have successfully modified wheat to withstand higher temperatures. However, none of these changes are reflected in the crops planted in the fields.
This needs to change if we are to feed a growing population on a hotter planet.
