Although sorghum is known to be much more heat- and drought-tolerant than its close relative corn, the underlying reason for this difference is not well-established. Solving this mystery may be key to developing corn that is more resilient to high temperatures and the often dry summer conditions in Nebraska and other parts of the Midwest.

A University of Nebraska–Lincoln team led by former postdoctoral fellow Lucas Busta, working in the lab of Ed Cahoon, director of the Center for Plant Science Innovation, has taken a big step toward identifying the biochemical and genetic basis for the large differences in the ability of corn and sorghum to tolerate environmental extremes. The research was recently published in the journal Proceedings of the National Academy of Sciences.

These differences, which make sorghum a grain and forage crop of choice for semi-arid climates, have been attributed in part to the large amounts of wax that coat sorghum’s leaves and stems and serve as a barrier to water loss, especially at high temperatures.

The research team discovered that sorghum not only has more wax on its surfaces than corn, but also a highly enriched, steroid-like wax on mature plants. The abundance of this particular kind of wax was missed in previous sorghum analyses.

The team also found that corn wax is devoid of this wax component. The steroid wax has been shown to “seal” the wax of some desert plants to further reduce water loss. Comparing the genomes of sorghum and corn, the team concluded that the key gene for steroid wax production is mutated in corn, resulting in the loss of its ability to make the steroid wax.

This was a big discovery, particularly for a young researcher, Cahoon said.

“He had his own fellowship, and I left him alone to do his work,” he said. “It wasn’t until he showed me the manuscript that I thought, ‘Wow, this is really interesting.’”

Busta, now an assistant professor at the University of Minnesota Duluth, is working with Husker scientist Tom Clemente to add the non-mutated sorghum gene to corn. The researchers hope the modified corn will gain the ability to make steroidal waxes for improved production in high-temperature, low-rainfall seasons and in regions of the world not currently suited for corn production.

“We’ve found an extremely interesting correlation, and the next step is to test this,” Busta said.

The Cahoon lab is also exploring the potential to divert a portion of sorghum’s high wax content to produce high-value oils as co-products in bioenergy sorghum. Those efforts are part of Cahoon’s work with the Center for Advanced Bioenergy and Bioproducts Innovation, which is sponsored by the U.S. Department of Energy and housed at the University of Illinois.

The research team also included Husker alumna Elizabeth Schmitz, James Schnable from Nebraska’s Department of Agronomy and Horticulture, and Dylan Kosma from the University of Nevada.

The study is available here.

Center for Plant Science Innovation Institute of Agriculture and Natural Resources