The key to drought-tolerant crops may be in the leaves
Researchers at USC Dornsife and Texas A&M University found that winter wheat plants grown in arid conditions with reduced irrigation protect themselves by producing thick leaf wax. Photo by Xiuwei Liu, Texas A&M University.

The key to drought-tolerant crops may be in the leaves

As water supplies decline in major agricultural states, Sarah Feakins of Earth sciences explores how to generate more drought-resistant food crops.
ByEmily Gersema

A solution to help farmers grow crops in dry areas or during stretches of drought may depend on breeding and cultivating plants that protect themselves with a thicker layer of leaf wax, a new study co-led by USC Dornsife’s Sarah Feakins shows.

Feakins, associate professor of Earth sciences at USC Dornsife, has taken her expertise studying leaf wax in the context of climate change and — for the first time — applied it to agricultural production. She teamed up recently with researchers at Texas A&M University to research and develop drought-resistant crops.

During tests that involved growing winter wheat, a type harvested for yeast-based breads and other such products, the team found that the cultivars, or plant varieties, in a high and dry area of Texas generated more protective wax on their leaves as a measure to protect themselves against more extreme conditions.

The results mimicked what scientists have found in leaves in natural ecosystems: Those that survive in dry climates have higher concentrations of wax.

“Water conservation depends on innovation, and in this case, we are hoping to find one solution by identifying the traits in this important food crop that would enable the wheat plants to tolerate drought and still produce plenty for harvest,” said Feakins, a co-lead author of the new study, which was published in the journal Organic Geochemistry on Aug. 14.

Dry versus regular moist conditions

Associate Professor of Earth sciences Sarah Feakins. Photo by Peter Zhaoyu Zhou.

All plants produce wax that helps their leaves repel water and shield the plant from insects and the elements, said Feakins, who studies the climate history of Earth through the geochemistry of leaf wax in sediments.

The United States is currently the top exporter of wheat in the world, according to the U.S. Department of Agriculture’s Economic Research Service. Winter wheat is largely grown for bread products and ingredients, such as all-purpose flour.

For the study, the researchers grew test plots of winter wheat in two different areas of Texas: the high plains of Amarillo and a farming area known as Winter Garden, Uvalde.

At each location, scientists grew 10 cultivars of winter wheat that received regular irrigation and another 10 cultivars that received 13 percent to 25 percent less irrigation. The team compared the leaf wax of all the plots to gauge their drought tolerance.

The plot set to receive 25 percent less irrigation in Winter Garden ended up receiving 13 percent less because of greater-than-expected rainfall. But a similar plot grown with 25 percent less water in the most arid area, Amarillo, generated 50 percent more paraffin on its leaves than the other cultivars in all the other plots, which enabled the plants to tolerate their dry conditions.

“We see a strong effect in the higher and drier location,” Feakins said. “We see the plants adapt to their environment and to better protect their leaves, allowing them to respond well to reduced irrigation.”

The lower available water was tracked through carbon isotopes in the plant leaves and in the waxes themselves — tools that are used to reconstruct climates of the past from ancient waxes in sediments.

“This is part of an effort to breed crops that are more drought-resistant,” Feakins said. “In the world that we are in today, with warming reducing available water, there will be more demand for crops that are drought-resistant.”

Feakins said the team will next consider which of their cultivated wheat crops offers the best resilience and are able to generate high yields with low irrigation or precipitation.

About the study

In addition to Feakins, other authors of the study were lead co-author Xiuwei Liu, Xuejun Dong (also corresponding author), Qingwu Xue, Thomas Marek, Daniel I. Leskovar, Clark B. Neely and Amir M. H. Ibrahim, all of Texas A&M University.

The study was funded by grants from Texas A&M AgriLife Research and the Texas Wheat Producers Board.