How do plants ward off pathogens? USDA-funded study seeks answers

Video: Texas A&M AgriLife

Two Texas A&M AgriLife Research scientists are studying the virtual tug-of-war that takes place when a pathogen attacks a plant. The pair received funding of almost $500,000 for a three-year study from the U.S. Department of Agriculture’s Agriculture and Food Research Initiative.

Both the pathogen and the plant undergo dynamic changes that improve their chances of victory. Better understanding these changes could unlock new ways to make the plants more disease-resistant, the researchers say.

“Specifically, we’re looking to improve the defenses of grasses that produce biofuel, like switchgrass, sugarcane and energy cane, as well as those that produce food, such as corn and sorghum,” said Kranthi Mandadi, an assistant professor and a plant genomics and molecular biologist at the Texas A&M AgriLife Research and Extension Center at Weslaco.

Grasses feed and fuel the world, Mandadi said. And the demand for more such crops will grow tremendously in the coming decades.

“The current worldwide estimate of cereal yields, which come from grasses, is just over 2,600 million tons, according to the Food and Agriculture Organization of the United Nations,” he said. “Agricultural economic analyses predict that global cereal demand will increase to more than 3,300 million tons by 2030.”

In addition, the demand for biofuel feedstocks will also increase to over 440 million tons in that time period. One way to help meet those future demands is to reduce the crop losses due to disease, he said.

Mandadi is collaborating in the study with plant virologist Karen-Beth Scholthof, a professor in the Department of Plant Pathology and Microbiology, College of Agriculture and Life Sciences, in College Station.

Improved grasses would have far-reaching implications, Scholthof said.

“Developing grasses better able to defend themselves against viruses and other pathogens would mean grasses with increased and higher-quality yields,” she said. “There are also potentially important environmental gains, including less water use and fewer fertilizer inputs,”

But until now, Mandadi said, little research has been done to study the defense mechanisms of grasses because of their complex genetics and long life cycles that can stretch from six months to several years. Some bioenergy grasses such as switchgrass are perennial.

Working with a smaller, faster-growing model grass reduces the time and expense normally associated with field research grasses, he said.

He and Scholthof found that working with diseases of grasses using model grasses such as Brachypodium and Setaria would be much more efficient. These two model grasses, developed by the U.S. Department of Energy for just such research, have a shorter lifespan of six to eight weeks and shorter stature, growing to only a few inches in height.

“This is convenient to test several plant generations with a greatly reduced need for field or laboratory space and resources, and in relatively less time,” Scholthof said. “And more importantly for science, the genetic makeup of these grasses is closely related to their field grass cousins.”