From ‘Weed’ to ‘Worthwhile’: Pennycress Makes Cover Cropping Viable

Corn and soybeans may be Minnesota’s mainstay crops, but they present a bit of an issue. Their growing seasons leave farm fields bare for long stretches of the year, leaving the soil to erode from the forces of wind, snow, and water.

On paper, the solution is clear: plant “cover crops” outside of the growing season that protect the soil’s fertility and prevent nutrients from leaching into groundwater and running off into nearby lakes and waterways. In practice, however, the method is extremely unpopular.

“There’s been this long history of trying to get cover crops on the land to cover that ground,” said Donald Wyse, PhD, professor of agronomy and plant genetics in the College of Food, Agricultural, and Natural Resource Sciences. “But it costs money to do that, and there’s no direct annual return to the farmer from it.”

That’s starting to change, thanks to years of research led by Wyse and David Marks, PhD, professor of plant and microbial biology in the College of Biological Sciences. Their combination of basic and applied science has resulted in the domestication of pennycress—a common weed that grows throughout most of North America—bringing growers across Minnesota an economically feasible cover crop option. Their domesticated version of pennycress has made the cover crop more appealing for industry by providing value-added, end-use oil and protein products. It is now moving towards commercial production.

Planted in the fall after the harvest of summer annual crops, pennycress can absorb nutrients like nitrate and phosphorus to prevent them from washing off into waterways and degrading the water quality. The plant is hardy enough to survive Minnesota winters and protect the soil beneath it. Pennycress’s flowers provide nectar and pollen to hungry pollinators, and the plant may lessen the need for herbicides by competing with weeds that emerge during the fall and spring.

Perhaps the most appealing part, however, is that growers can harvest pennycress’s seeds. The seed oil can be sold for a number of potential uses, such as for biodegradable packaging materials, lubricants, biofuels, and even an edible ingredient in foods like granola bars. Meanwhile, the seed meal (what’s left after extracting the oil) carries proteins, essential fatty acids, and fiber that make it appealing for food and animal feed. The seed meal can also be used as an organic fertilizer.

The Fast Road to Domestication

Despite pennycress’s potential, the plant was unfit for cover cropping in its wild form. Its seed pods shatter too easily, it takes too long to reach maturity, and certain acid compounds in it make it unfit for humans or animals to consume. The process of domesticating pennycress, or breeding out these negative attributes and selecting desirable ones, was what transitioned it into a valuable crop—and it happened much more quickly thanks to a serendipitous collaboration between Wyse and Marks.

Marks’s training is in basic research, driven by curiosity with the aim of building the body of knowledge on a subject. He spent a large portion of his career working on the genome of Arabidopsis, the “white mouse” of the plant world. In much the same way as a scientist might model an experiment in a fast-growing lab mouse before moving on to other, slower-growing animals or to clinical trials, Arabidopsis provides biologists with a fast and easily grown model for gene studies in plants. Researchers can use it as a shortcut of sorts to see how changing a specific gene affects the traits the plant has.

While Wyse also has a background in basic research, he has long focused on applied science, which aims to answer specific questions that contribute to solving practical problems. He became interested in domesticating pennycress in 2013 as part of his work in the Forever Green Initiative, a CFANS-based program to develop new crop varieties that both strengthen the agriculture industry and protect the environment.

Wyse had seen a presentation Marks gave on Arabidopsis several years before, and knew Arabidopsis and pennycress were close genetic relatives. He approached Marks about joining the project.

“I was well primed when Don came to me with this proposition to look at this plant pennycress that could address an important problem,” Marks said. “My work on Arabidopsis provided me with just the right background to quickly move pennycress toward domestication.”

Their collaboration allowed the work to move much more rapidly. Guided by the Arabidopsis model, they induced mutations in pennycress and grew many iterations of it out in the field. Each time, they sequenced the genomes of the ones that showed the most appealing qualities and used them to further refine the plant. Along the way, countless undergraduate students aided the field research, driven in part by the idea that they could make discoveries on an emerging crop.

“It has been a real nice tool for capturing the imagination of these undergrads,” Marks said, adding the experience has encouraged many of them to pursue graduate school.

Pilot studies are now in progress throughout central and southern Minnesota. These studies are testing out the environmental and economic benefits of domesticated pennycress and optimizing the methods used to plant and harvest it. A collaboration called Integrated Pennycress Research Enabling Farm and Energy Resilience (IPREFER) has linked the Forever Green Initiative and a handful of industry and university partners in the Upper Midwest to optimize and launch pennycress production as a cash cover crop.

With help from UMN Technology Commercialization, the researchers have also licensed several of the domestication traits they developed to CoverCress, a Missouri-based company developing pennycress with specific traits to make it ideal for cover cropping.

Seeding New Collaborations

The process of domesticating pennycress and moving it to market never would have reached this point without the combination of basic and applied research.

While a large institution like UMN has plenty of academic expertise to fuel future collaborations like this one, Wyse and Marks said the current structures can make it challenging to find and support interdisciplinary opportunities. They see an opportunity for the University to introduce more mechanisms for facilitating conversations and making connections across disciplinary boundaries so more collaborations like this one can take place.

“If you have this connection, it raises the tide and the outcomes across both the basic and applied areas of activities for an institution like this,” Wyse said. “If you bring those two together, you get better outcomes for society.”