Heat is coming for our crops. We have to get them ready

Source: The Conversation (Au and NZ) – By Mohan Singh, Professor of Agri-Food Biotechnology, School of Agriculture, Food and Ecosystem Sciences at the University of Melbourne., The University of Melbourne

Australia’s vital agricultural sector will be hit hard by steadily rising global temperatures. Our climate is already sensitive to droughts and floods. Climate change is expected to exacerbate this, causing sudden flash droughts, changing rainfall patterns and heavy flooding rains. Farming profits have fallen by 23% in the 20 years to 2020, and this trend is expected to continue.

If left unchecked, climate change will make it more difficult to produce food on a large scale. We get more than 40% of our calories from just three plants: wheat, rice and corn. Climate change poses very real risks to these plants, with recent research pointing to the possibility of synchronized crop failures.

Although we have long adapted our crops to repel pests or increase yields, until now no commercial crop has been designed to tolerate heat. We are working on this problem by trying to enable soybean plants to tolerate the extreme weather of a hotter world.

What threat does climate change pose to our food?

According to estimates by the UN Food and Agriculture Organization, food production will need to increase by 60% by 2050 to feed the expected 9.8 billion people on the planet.

Every 1°C increase in temperature during harvest seasons is associated with a 10% decrease in rice yield. A 1°C increase in temperatures could lead to a 6.4% drop in wheat yields worldwide. That’s as if we left out a major crop exporter like Ukraine (6% of traded crops before the war).

Plants, unlike animals, cannot take refuge from heat. The only solution is to make them better able to tolerate what is to come.

These events are already coming. In April 2022, farmers in the Indian state of Punjab lost more than half of their wheat harvest due to a scorching heat wave. This month, scorching temperatures in Southeast Asia are devastating crops.

What happens to plants when they experience extreme heat?

Plants use photosynthesis to convert sunlight and carbon dioxide into sugary foods. If it is too hot, this process becomes more difficult.

More heat forces plants to evaporate water to cool themselves. If a plant loses too much water, the leaves wilt and growth stops. A plant’s solar panels – the leaves – cannot receive sunlight when they wither. No water, no energy to make the fruit or grain we want to eat. When the air temperature reaches 50°C, photosynthesis stops.

Higher temperatures can make it harder for plants to produce pollen and seeds, and can cause them to bloom sooner. Heat weakens a plant, making it more vulnerable to diseases and pests.

Our seed crops – from rice to wheat to soybeans – depend on sexual reproduction. To get a good yield, the plants must be fertilized (pollinated by, for example, bees and flies).

If a heat wave hits during the fertilization period, it will be more difficult for plants to set their seeds and the farmer’s yield will decrease. Worse yet, high temperatures cause sterile pollen, which reduces the number of seeds a plant can produce. Pollinators such as bees also find it difficult to adapt to the heat.

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Preparing our crops

To give our crops the best chance, we will have to use genetic modification techniques. While these have often been controversial, they are our best chance to respond to the threat.

The reason for this is that genetic modification gives us more precise control over a plant’s genome than the traditional method of breeding for specific traits. It is also much faster because we can isolate genes from one organism and transfer them to another organism without sexual reproduction. Although we cannot cross sunflowers with wheat through sexual reproduction, we can transfer sunflower genes to wheat.

For decades we have relied on genetically modified versions of some of our most important food and fiber crops. Nearly 80% of the world’s soybeans have been genetically modified to increase yields and make them more nutritious. Genetically modified canola accounts for more than 90% of production in Canada and the United States, while approximately 20% of canola grown in Australia is genetically modified. But until now we have not had commercially approved crops adapted to withstand heat.

One way to do this is to look for heat-tolerant plants and transfer their qualities to our crops. Some plants are remarkably heat tolerant, such as the living fossil Welwitschia mirabilis, which can survive in the Namibian desert with almost no rainfall.

Heat shock and heat sensors

Plant cells possess heat shock proteins, just like ours. These help plants survive the heat by protecting the protein folding process in other proteins. If there were no heat shock proteins, vital proteins would unfold instead of folding into the right shape for their job.

We can try to enhance the function of these existing heat shock proteins so that the cells can continue to function under warmer conditions.

We can also modify the behavior of genes that act as heat sensors. These genes act as master switches, regulating a cell’s response to heat by summoning protective heat shock proteins and antioxidants.

In our laboratory, we modified soybean plants by enhancing these heat-sensitive master switch genes. Soybean plants expressing higher levels of this gene showed a significant increase in protection. Under short, intense heat wave conditions, these modified plants wilted less, produced more viable pollen, showed fewer structural deformities, and had better yields 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 change wheat – the main staple crop.

Heat waves pose a similar problem for wheat, but there is no community acceptance. Resistance to modified wheat has been very strong.

In the laboratory, researchers from universities and agricultural companies have succeeded in modifying wheat to tolerate more heat. But none of these changes have resulted in crops being planted in the fields.

If we want to feed a growing population on a hotter planet, this will have to change.

Read more:
Climate change threatens to cause ‘synchronized crop failures’ around the world, impacting Australia’s food security

Research in Mohan Singh’s laboratory has been funded over the years by the Australian Research Council (ARC). In addition, the University of Melbourne provided funding for the research.

Prem Bhalla had received funding from the Australian Research Council and the University of Melbourne.

– ref. Heat is coming for our crops. We need to get them ready – https://theconversation.com/heat-is-coming-for-our-crops-we-have-to-make-them-ready-223553