To Secure the Future of Food, Look to the Ancestors of Eggplant
To Secure the Future of Food, Look to the Ancestors of Eggplant
In a greenhouse in tropical southern Taiwan grows a small tree. From its hardy trunk sprout stems with wide, fuzzy leaves and sprays of white star-like flowers. Some of these flowers have already transformed into inedible green fruits about the size of marbles. Mohamed Rakha, a plant breeder here at the World Vegetable Center, splits open one of the fruits with his fingernail. “You can see a lot of seeds inside,” he says. Each one is packed with the plant’s DNA—and lots of potential.
Odd as it may seem, this fruit—a wild eggplant—is an ancient relative of the big purple eggplant sold in grocery stores worldwide.
At the World Vegetable Center, experts are studying a wide variety of eggplant relatives for their hardiness and ability to produce appealing, edible fruits—but it isn’t typical, business-as-usual breeding. Rather, plant breeders are on a mission to save the human diet from climate change.
All of the fruits and vegetables available in markets and grocery stores today are products of domestication. Their ancestors were not-so-edible organisms like the little tree Rakha tends. But centuries ago, humans began to take the biggest and tastiest wild plants and breed them together. They repeated this over and over, weaving together the genes that made a juicier fruit or a fatter wheat kernel so that many generations down the line, modern plants are now quite different.
These domesticated plants, despite their advantages, have some significant weaknesses. They’re not as sturdy as many of their wild relatives when it comes to resisting diseases, droughts, and other challenges. When a problem arises, they do not have the genetic diversity that allows wild populations to ride it out—all the individuals are so similar that what kills one, kills them all. And crops are already facing a serious challenge that’s bound to get worse: climate change.
As temperatures warm and pests shift their territories around the planet, large swaths of the human diet are at risk of crumbling under the onslaught of disease, insects, saltier water, and unbearable heat. Scientists estimate that U.S. corn, the country’s dominant crop, will see a decrease in yield of about 50 percent with a 4-degree Celsius temperature rise, which is predicted by the end of this century. In the later years of the 21st century, increased ozone in the atmosphere and lack of water due to climate change may reduce yields of vegetables by more than 30 percent, another study found.
These crops’ wild relatives—spunky, straggly plants—might be able to help. Breeders think that if they can collect seeds from these relatives, they may be able to breed resistance to drought, heat, and other threats back into the crops we depend on. But time is short. And so, in a daring move, scientists under the direction of the Global Crop Diversity Trust—based in Germany—have hatched a plan called the Crop Wild Relatives project. Starting in 2011, with 10 years of funding from the government of Norway, they set out on a mission.
In seed “safaris,” hundreds of scientists have fanned out in tall grasses, deserts, and remote mountains looking for wild relatives of staple food crops around the world. Since 2015, these missions have yielded 3,800 samples from 24 countries, including wild carrots from Bangladesh, wild eggplants from Tanzania, and wild sweet potatoes from Nigeria. The Kew Gardens Millennium Seed Bank in the United Kingdom has helped distribute the newfound seeds to breeders and researchers, who will grow them to find out exactly what their strengths are. In this global scheme, the World Vegetable Center in Taiwan is where the wild relatives of domesticated eggplant will get put through their paces.
Standing Up to Pests
The World Vegetable Center, founded in 1971 to develop crops for Asian countries, is headquartered in a cluster of low buildings ringed with fields just north of the city of Tainan. Palm trees dot the grounds between glass greenhouses where staff members conduct experiments and maintain the center’s enormous collection of seeds.
On a cloudy day in October, Maarten van Zonneveld, the manager of the center’s seed collection, walks through the greenhouse where the wild eggplants will be grown, pointing out the beds built for new seedlings. The idea is that when the researchers find a plant that can stand up to a pest or keep producing despite a big jump in temperature, they will breed that wild variety with a standard, domesticated crop variety. If they manage to get a hybrid, they’ll keep refining it over the course of many generations.
This isn’t always a simple procedure because, just as with humans, offspring may not resemble their parents. If the offspring, which gets half its DNA from the wild relative parent, only inherits some of the genes necessary for a desired trait, it won’t benefit from it. And of course, the plant has to continue to produce lots of tasty vegetables as well. This process, called pre-breeding, can often take eight to 10 years or longer, just to get to the point where a seed company could take over.
“For a seed company, a long-term project is two to three years,” says Philipp Simon, a USDA carrot breeder who leads the Global Crop Diversity Trust’s wild carrot project. “A seed company doesn’t want to work with a wild carrot relative—that would take forever from their frame of reference.” So pre-breeding, which creates the materials for mainstream breeders to use in their work, usually happens at universities and public institutes like the World Vegetable Center.
Eighty-nine new wild relatives of eggplant have been collected and will be grown at the center over the coming years. But in parallel, while those efforts get off the ground, the center’s collaborators at the University of Valencia in Spain have started to forge ahead using wild eggplant relatives that were already in gene banks. Geneticist Jaime Prohens and his group there have drawn on samples from Asia and Africa, as well as two distantly related American relatives, over the past several years. “This means crossing eggplant with a species that separated about 20 million years ago,” says Prohens—an exciting, if difficult, task because they have very different genes.
To its surprise, Prohens’ team has already managed to get fertile hybrid plants from many crosses and, with some lab work, coaxed seeds from a few others. These will mix eggplant genes in new ways, and the most interesting specimens have arrived at the World Vegetable Center, where they will be evaluated for resistance to pests.
In the greenhouse, Rakha lifts the leaf of a potted cabbage plant to reveal hundreds of tiny whiteflies, which suck the sap out of eggplant leaves. The center keeps thriving populations of common crop pests like whiteflies in a special greenhouse for such experiments. Rakha and his colleagues hope that the new, hybrid plants will stand up to their scourge.
As researchers record what all these fresh infusions into the domesticated eggplant’s gene pool do in the field, the information will be entered into a database that anyone around the world can access, says Benjamin Kilian, the manager for the project at the World Crop Diversity Trust. “All pre-breeding data will be freely available,” he says.
An Open Vault
How swiftly might insights from the wild relatives project hit grocery store shelves? That depends on what researchers find and how seed companies decide to make use of the breeding material. Five seed companies are collaborating with the World Vegetable Center on the eggplant work, testing the new plants in their own fields. “These companies might select [the] most promising materials for their own breeding,” says Kilian, which would accelerate the eggplants’ arrival in stores. So far, no eggplant from the project has reached the consumer phase.
In just two years, the current funding for the Crop Wild Relatives project will end; partners and other stakeholders will have selected the most promising pre-bred materials and integrated them into their breeding pipelines by then. But the project’s legacy will remain in the seed banks of the world.
Van Zonneveld visits World Vegetable Center seed bank curators Yung-kuang Huang and Tien-hor Wu—“There are not many people who have seen more eggplant diversity than Mr. Wu,” Van Zonneveld says by way of introduction—and together the three scientists go down white corridors and up a flight of stairs to the door of a vault. Inside, it’s a frigid 41 degrees Fahrenheit. Heavy rolling shelving units can be pushed apart to reveal thousands of little silver envelopes, each one containing the legacy of a plant. “This represents a part of the history of man and plant,” says Van Zonneveld. “It’s one of the—if not the largest—public international gene bank of vegetable germplasm.” A thermostat senses the heat of our bodies and industrial fans slam on, sending a wave of cold air over the room and its precious contents, which anyone willing to do the import paperwork—seed company employee, scientist, interested gardener—can request.
Wild relatives are not immune to troubles, as construction projects and other disturbances frequently threaten to encroach on their habitats. Still, they can be found in the most unlikely of places––it just takes a little practice to recognize them. Phillip Simon, the carrot breeder, has collected wild carrots by the roadside in Turkey, Tunisia, Uzbekistan, and Turkmenistan.
“My first collecting trip was to what was at the time the USSR in 1989,” he says. In the United States Department of Agriculture’s gene bank are purple carrot seeds he collected near Homs, Syria, many years ago, which may not exist there anymore. The USDA has funding available for collecting missions focused on wild relatives, although not many scientists realize it, Simons says. And within the U.S., there are amateur groups that go out collecting as well, on the hunt for wild garlic and onion and carrots—the global seed safari, on a much smaller scale.
On the other side of the world in Taiwan, Van Zonneveld spotted a mung bean relative in the wild recently, and he brought it back to his office to press it. Now he carefully lifts a sheet of newspaper to reveal the delicate curl of the dried plant. Its unassuming yellow flowers not yet gone to seed, they resemble those of their much more famous cousin, a crop eaten by millions. For him, it represents the promise of a better future.