How to breed a climate resilient sunflower? Look to its ancient cousins.

Already capable of growing in harsh conditions, sunflowers have the potential to withstand even more.

The trend is clear, says Brent Hulke: The climate is changing in North Dakota and sunflowers are working harder to survive.

Hulke is a research geneticist specializing in sunflowers in the U.S. Department of Agriculture’s (USDA) research facility in Fargo, North Dakota. He helps breed better versions of the domesticated plant, Helianthus annuus, whose seeds we snack on and whose oil we cook with. It’s here that breeders make sunflowers more resistant to diseases, increase their Vitamin E content, or change their fatty acid compositions to make them healthier.

It’s also where sunflowers might get help adapting to climate change.

“The precipitation trend is undeniable,” Hulke says. “Farmers don’t have to be climate change believers or deniers. They know it’s wetter than it used to be when they were kids.”

All that rain—a result of the warmer atmosphere holding more water vapor—has been spreading more diseases and making the development of new sunflower varieties more urgent. And it’s not just rain and floods that farmers must contend with in the Great Plains; climate change will lead to more intense droughts as well. The combination will make soils saltier, forcing crops to work harder to find fresh water.

Sunflower roots typically extend twice as deep as those of corn and soybeans—nine feet in some cases—which lets them tap into more water and gives the sunflower a survival edge. But as growing conditions become less predictable, sunflowers must tolerate even tougher conditions.

“As plant breeders, we have to be focused on climate change. That has to be what alarms us,” says Hulke.

To prepare for that uncertain future, scientists are trying to protect sunflowers’ wild ancestors and the evolutionary advantages locked away in their DNA. Just like dogs descended from wolves, common crops like corn, wheat, and sunflowers evolved, with human help, from wild varieties of plants growing in a range of environments, from wetlands to deserts.

And while the USDA houses more than 2,000 samples of 63 different sunflower species and subspecies in gene banks—all members of the genus Helianthus—scientists say the environments they grow in also need urgent protection if we’re to learn how to improve sunflower crops enough to maintain production in an increasingly unpredictable climate.

“If we were to put everything in cold freezers and consider ourselves done, we would no longer be interested in the evolution [of the species] and that can be very, very important in terms of developing resistance or adapting to climate change,” says Colin Khoury, a crop diversity specialist at the International Center for Tropical Agriculture in Colorado.

Last December, Khoury and his colleagues published a study arguing that a number of wildflower species, including sunflowers, needed urgent protection. And in 2019, a study by Laura Marek, a sunflower curator for the USDA, concluded the same.

Now or never 

There’s evidence of sunflowers being grown by the ancient inhabitants of Mexico nearly 5,000 years ago and of Native Americans domesticating the flower in the eastern United States around the same time.  When Europeans arrived in the Americas, the flowers became a prized cut-flower decoration and were brought back to EuropeThey were painted by the likes of Anthony van Dyck and Vincent Van Gogh,

A more efficient way to breed them was developed by 19th century Russians, and today, sunflowers produce the third most popular cooking oil globally, behind canola and palm. In the U.S., where a majority of sunflowers grow in North and South Dakota, nearly 900,000 metric tons of sunflower seeds are produced every year. But it trails behind countries like Russia and Ukraine, which produce ten times that on an annual basis. 

“Sunflower is considered to be one of the more environmentally resilient crops,” says Loren Reiseberg, an evolutionary biologist and sunflower expert at the University of British Columbia, mainly because the roots are so deep that they don’t need to be irrigated or fertilized. But as hardy as it is, breeders will need the genetic diversity of its family members to help it withstand global warming.

“It is a crop that’s very well suited for climate change, in part because you have the wild relatives, which give it options for creating more environmentally resilient cultivars,” says Reiseberg.

Marek, who’s been collecting sunflowers for nearly two decades, says even though the USDA has a large collection of the genus’ genetic material, for some of the more threatened species, “climate change makes it now or never.”

In the Southwest in particular, she worries conditions may chip away at sunflower populations.

“It’s killing everything there. It’s getting too hot. Too dry. Climate change is going to be the worst thing,” for these species, she says. 

Conserving wild species doesn’t come easily

“In September you can sit out there and bathe in sunflowers, and the world is a happier place,” says Daniela Roth, a New Mexico state biologist.

Roth runs the state’s endangered plant program, and the sunflower she’s referring to is listed as threatened on the Endangered Species List and endangered by the state of New Mexico. It’s the Pecos sunflower, Helianthus paradoxus, found only in New Mexico and parts of West Texas. Unlike its domesticated cousin, it grows in salty wetlands called cienegas, a type of ecosystem found only in the Southwest.

That ability to survive in a salty environment, which Roth argues is valuable in its own right,  may become more valuable in a hotter, drier future of saltier agricultural soils, as scientists look for ways to breed salt tolerance into commercial crops.

But the only official protection for the Pecos sunflower, despite its rarity, lies within a 116-acre preserve called Blue Hole Cienega in Santa Rosa, New Mexico. And while careful management there has helped the plant’s numbers grow in the past eight years, Roth worries that climate change and the region’s ever-scarcer water could trump her efforts and harm the wetland environment the Pecos needs to survive. 

“It doesn’t matter what I do in terms of management if there’s no more water to germinate the seeds in the spring,” she says.

Why just one isn’t enough 

Currently there are three sunflowers on the federal endangered species list, including the Pecos, and 13 others are listed as threatened in certain states, according to the USDA.

There’s the whorled sunflower, Helianthus verticillatus, listed as endangered, found only in a few scattered populations in Mississippi, Tennessee, Alabama, and Georgia. It was first discovered in 1892 and later thought to be extinct until it was rediscovered in 1994.

The Schweinitz’s sunflower, Helianthus schweinitzii, is found only in North and South Carolina and also endangered. Unlike the common sunflower, growing on a thick stalk with one large head, the Schweinitz’s sunflower has multiple, daisy-like heads. Like many sunflower relatives, it could almost be confused for a harmful weed, albeit one with a pretty flower.

“I’ve been working on sunflowers for 40 years now,” says Gerald Seiler, a research botanist at the USDA. “My job is to take the things that grow along roadsides and ditches. I'm trying to preserve them. Sunflowers are considered a weed in a lot of areas.”

He and Marek hunt down and collect wild sunflowers. Their seeds are then stored at the USDA’s Plant Introduction Station in Ames, Iowa, which essentially functions as a genetic library.

It’s not enough, says Marek, to collect a sample from one location. For example, she says, the silver leaf sunflower, “which was collected on Daytona Beach in Florida, turned out to have resistance to rust pathogens in the United States at the time.”

The same silver leaf sunflowers collected in other regions, however, did not.

“Do we have enough? To me, we’ll never have enough,” says Seiler, but he adds, “I think we have enough if we ever get into a crisis. The sunflower gene banks are in very good condition now.”

But scientists worry what information might be lost if a species isn’t conserved in its natural habitat.

“As we speed up the change in our climate, it gets harder to predict what’s coming,” says Khoury. “In seed banks we’re doing pretty well. The natural habitats are the side that needs more focus.”

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