Tolerance Is The Word As Agricultural Scientists Try To Combat Climate Change

Resilience is the name of the game for plants when it comes to changing climate conditions on Earth. The crops we rely on to feed most of the planet need to be reinvented to deal with drought, floods, salinity, heat, disease, and insect and other pests.

Many staple crops have evolved natural resilience and tolerance to changing climate conditions like El Niños. Recently, however, climate predictability is going by the wayside with ramifications for food security.

Of all staple crops, rice is the one most eaten globally and has been most imperilled by climate change in recent decades. In Asia, 75% of calories consumed come from eating rice, which is extremely heat-sensitive. When an El Niño event happened in 2015, heat contributed to a 15 million-ton drop in rice production throughout Southeast Asia. Rice prices caused a 16% inflationary bump.

Philippine researchers have linked temperature increases to rice yield declines. The ratio is for every 1 degree Celsius rise in the minimum temperature during the growing season, yields decline 10%. That’s why agricultural scientists are targeting the rice genome to identify those genes related to heat tolerance of which there are 97.

Wheat is another global staple crop feeling the effects of global heating. In Asia, every 1-degree increase in minimum temperatures translates to a 6% decline in wheat yields. That’s why agronomists are testing 3,322 new wheat varieties since 2021 with the hope of identifying strains that produce better yields in more extreme heat conditions.

Developing new varieties of wheat and rice can be done through conventional cross-breeding. Increasingly, however, genome editing is preferred because compared to conventional breeding which can take multiple generations to produce results, genetic engineering is much faster taking less than a third of the time.

Hiroshi Maeda, a professor of botany at the University of Wisconsin in Madison is working on modifying citrus crops like oranges and grapefruit. In the United States citrus farmers face devastating challenges from climate change including extreme weather events and freshwater scarcity. Maeda and his colleagues have also taken the genetic modification route to make citrus climate resilient. He states:

“Climate change is happening so fast that classical breeding approaches are not enough to overcome the challenges we are facing. It took 10,000 years for us to domesticate the crops, and we do not have that kind of time. We must accelerate the process using biotechnology, gene editing and transgenic approaches.”  

Another staple crop is sorghum which is closely related to corn and an ingredient used to make cereals and pasta. Areas where sorghum is grown in the United States have witnessed extreme temperature changes in recent times with an expanding Arctic polar vortex causing chilling stresses and crop losses.

Rebecca Roston, a plant scientist at the University of Nebraska-Lincoln, is studying plants like sorghum and how they respond to temperature changes, especially cold. Her research looks at the lipid composition of plant cell membranes and how they withstand freezing temperatures. States Roston:

“The reality is that the cold has driven human habitation and agriculture for millennia, and it is a problem that is so big that we don’t see it because it’s opportunity loss, not direct crop loss.”

Roston is using lipidomic sequencing to analyze sorghum and a cold-tolerant cousin plant, foxtail millet, and to understand the metabolic influences that affect crop stress. Unsaturated fatty acids contained within the plant membrane are key to promoting plant survival at low temperatures.

Soybeans have proven to be sensitive to disappearing ozone caused by increases in greenhouse gasses and smog. Notes Joseph Jez, a professor of biology at Washington University in St. Louis, a 1% decrease in the ozone layer corresponds to a 1% drop in soybean yields and since 1979, the ozone threshold has plummeted by more than 47%. That means a race against time to up the ability of soybeans using gene editing and modifications in the face of a more hostile growing environment. Jez notes:

“The plants we have now are not going to be the plants we have in 2050. The big unknown is whether we can either breed or edit the path forward to make plants survive the climate of 2050 or 2100.”

Climate-resilient future crops like corn, rice, sorghum, soybeans and wheat are being epigenetically modified to deal with drought and heat. Rice is being altered genetically to survive flood-prone growing areas. These staple crops are re-engineered to tolerate higher salt levels in the soil as sea levels rise. Re-engineered to withstand diseases, fungi and insect pests, plants are being weaponized against all of these.

In addition, scientists are enhancing photosynthesis in plants to help them grow faster. Root systems are being engineered to go deeper to find water and to become carbon sequestration storage sites. And finally, plants like rice are being modified to use less water and produce lower methane emissions from paddies.

It is a brave new world we face as the planet heats up and agronomists and geneticists try to develop new armour for our plants to survive the anthropogenic climate change that is taking hold in the 21st century.