Grain of Doubt
Overuse of corn has clouded the image of America's biggest crop. Can genetics help reshape corn's future?
Like a swarm of fireflies, a group of teenagers creates a chaotic dance of flashlight beams as they scatter down a path leading into Don Schuster’s corn. Within moments, they are gone, swallowed by the deepening blackness of the tall corn and the encroaching fall evening. Only their voices drift back to us, standing on the periphery of the nine-acre field. Others, too—the excited peal of children and young couples who have come to wander the serpentine paths Schuster has carved into his corn. Their laughter floats above us like the whispers of ghosts, happily lost in this maze of maize.
Strange phenomena, corn mazes. Schuster BS’86 MS’94 has been creating them for nine years on his farm near Deerfield, Wis., and he’s still uneasy about tearing up good corn to make a human-sized rat race. “It goes against everything I was brought up to think about a cornfield,” he says. But as a part-time economist with CALS’ Center for Integrated Agricultural Systems, he also understands the bottom line. In a good year, 11,000 people will pay two to six dollars each to get lost in his family’s field, enough to make whatever money he gets from the corn itself incidental.
This would have seemed a bizarre reality to Schuster’s ancestors, who farmed corn for four generations before him. But if those men could walk through Don Schuster’s field today, they would be lost for a different reason. The plants that towered around them would look alien, hardly resembling any cornfield they would have known.
Seventy years ago, Schuster’s grandfather might have planted 8,000 corn seeds per acre, leaving plenty of room for the stalks to spread out. Today, most farmers put in 30,000. Schuster goes beyond that: To enhance the closed-in feel of his maze, he plants rows in both directions, packing 44,000 stalks into each acre. By August, his corn forms an eight-foot-tall wall with a canopy so thick that sunlight hardly reaches the ground.
“That’s a lot of what makes people enjoy the maze,” says Schuster. “You get in there and you can’t see over the corn. It’s like a big tunnel.” But it’s an effect created not by light or darkness or by Schuster’s zero-turn-radius mower. It owes its magic to the plant itself, and the human conquest of it. We have made corn a jungle.
Through 7,000 years of farming, humans have turned a wild grass that grew in the valleys of Central America into Zea mays, one of the most bountiful food crops in existence. Today, corn grows on every continent except Antarctica, from the American heartland to the northern plains of China to the Andes mountains. Worldwide, farmers harvest some 700 million metric tons of its kernels each year, making it the second-largest food crop on the planet, behind sugarcane.
Ample credit for that dominance goes to the generations of farmers and breeders who have tailored the genetic superiority of the corn plant. Like a thoroughbred race horse, modern corn is a rare beast, designed to perform. It has been honed to grow taller and healthier and live closer to its neighbors, traits that have driven per-acre corn yields to historic levels. While 80 years ago American farmers yielded about 26 bushels of corn from one acre, now they often haul in more than 200.
Although corn occupies about 20 percent less land now than it did before World War II, our nation’s annual corn harvest has more than quintupled. Last year, farmers harvested a record-busting 13.1 billion bushels of corn—enough to supply every man, woman and child in the country with a six-and-a-half pound box of kernels every day for an entire year.
Of course we don’t eat all of that corn, at least not as kernels. Only about 12 percent of the U.S. corn crop goes directly into food production; the rest is fed to animals, turned into products such as ethanol or exported. But corn finds its way back to us in many ways—as sweeteners like high fructose corn syrup and dextrose, as starches in baked goods and confectionaries, as cooking oils and margarine, and as proteins and enzymes added to hundreds of foods. More than one quarter of the items on supermarket shelves now contain some form of corn, from Twinkies to fruit juice, from waffles to salad dressing, from soup to nut bread. Order a typical fast-food meal and you’re eating corn in every bite: Corn feeds the cattle that make the beef; corn enriches the bread in the bun; corn sweetens the soda and bathes the French fries to golden perfection. It’s even in the ketchup.
And therein lies the problem. As much as we have ruled corn, corn now rules us. It’s in our T-shirts and boxer shorts and our children’s disposable diapers. It’s in our vitamins and our prescription drugs. It’s in lipstick. It’s in soap. Corn starch is in the finish applied to these magazine pages, the cardboard boxes they were shipped in and the gasoline tanks of the vans that delivered them. Our daily lives have come to rely so heavily on corn that 13.1 billion bushels of it seems hardly enough. Increased demand for corn, especially from foreign markets and the ethanol industry, has pushed corn prices to historic highs, more than tripling in the past two years. After summer floods in Iowa and Wisconsin raised fears of a poor harvest, corn spiked to near $8 a bushel, a level never before seen.
With corn now blanketing a swath of U.S. soil that could cover half of Texas, planting more hardly seems appealing. Nitrogen and phosphorus runoff from cornfields in the Mississippi River basin is contributing to a growing dead zone in the Gulf of Mexico, where excess nutrients cause oxygen levels to drop and make water inhabitable for fish. Growing more corn would exacerbate those problems, especially since most of the lands best suited for corn are already planted with it. If farmers choose to till highly erodable grasslands for corn, soil erosion and runoff problems are bound to get worse.
But the real trouble with corn may not be what it does wrong, but what it does right. Corn is among an elite collection of plants, including sugarcane and switchgrass, that has evolved a super-efficient way of capturing sunlight and carbon dioxide from the air, known to botanists as C-4 metabolism. C-4 plants soak up these energy sources without wasting water, which allows them to store more energy and tolerate heat and drought better than others. Plant one seed of corn and you’ll get 400 seeds in return. Do the same with wheat or soybeans and you’ll get little more than 100.
This advantage made corn desirable to the early farmers who first domesticated it—and to virtually every western civilization since. When Native Americans introduced European settlers to the crop, the newcomers quickly abandoned the wheat they’d carried across the Atlantic and embraced corn as the foundation of their survival. Two hundred years later, as corn seeds found their way across the globe, British scientist William Cobbett would write that the plant “was the greatest blessing God ever gave to man.”
But corn’s eager submission to humans’ will may also explain why its great success now borders on excess. “Farmers want to grow corn because it’s very good at what it does,” says Bill Tracy, who leads CALS’ sweet-corn breeding program. “The issue is that because it’s so good at what it does, we have 80 million acres of it.”
Is this the fate of corn, to be so loved it’s hated?
Statues of Mayan corn gods stand atop the bookshelves in Bill Tracy’s office, keeping watch over the accumulated treasures of a life spent pursuing corn. Tracy’s desire to breed the perfect kernel has taken him throughout the western hemisphere, from the black soils of Wisconsin to the remote wilds of Chile and Argentina. The last time he wasn’t growing corn somewhere in the world, Jimmy Carter was president.
It’s hard to say which Tracy enjoys more, growing corn or eating it. Occasionally, those activities intersect: In the fall, after he and his staff harvest corn from the program’s 20-acre research plot at the West Madison Agricultural Research Station, he walks along each row, sampling ears. Most years he’ll taste 500 different varieties of sweet corn, noting subtle differences in each.
But Tracy also knows the plant he admires is troubled. “Corn is a technology,” he says, “and technologies can be misused. As much as I love it, I do worry that we’re leaning too heavily on corn.”
The advantage of Tracy’s job is that he can do something about it. Breeders in positions like his have played no small role in the modern evolution of corn. It was the work of academics George Shull and Edward East, who a century ago began mating inbred lines of corn to test the powers of genetics, that revealed the promise of hybrid corn varieties. Another professor, a man named R.A. Brink, who had studied with Shull and East, brought hybrids to Wisconsin when he was hired by the College of Agriculture in 1923. The college’s first hybrid line was released in 1933, and within eight years, 90 percent of Wisconsin’s cornfields were growing hybrids. By 1958, average yields had doubled, and the state’s overall production had more than tripled. Former CALS Dean Glenn Pound PhD’43 would later say that the college’s hybrids boosted the value of the state’s corn crop by $20 million a year between 1950 and 1970.
University breeding programs have since faded into the background of a picture dominated by the giants of the for-profit seed industry. Two companies—Monsanto and Pioneer Hi-Bred—now control more than 60 percent of the corn seed market. Certainly, the landscape changed with the emergence of genetically modified seeds, which were introduced by Monsanto in the 1980s and now comprise more than two-thirds of the corn planted in the United States. But an erosion of funding for crop research has helped diminish the role of public breeding programs. Of the dozens of university plant breeding programs that were birthed by the hybrid revolution, only a handful remain. Those survivors often struggle for grants and graduate students, who are often lured by higher-paying jobs in industry. In a world of genetic engineering, plant sex just isn’t as sexy. But life on the periphery has its benefits, and one of the biggest is that Tracy doesn’t have to worry much about the demands of the market. While his program does release the occasional sweet-corn hybrid, his primary mission is to experiment with the genetic limits of the plant. “Commercial breeders are driven by their business not to stray too far from what’s working,” he says. “As a university breeder, I can go to material that is maybe too wild or too exotic for somebody who is trying to turn out a new hybrid.”
And few plants offer so much room to experiment as corn. Although you might not suspect it from looking at the orderly symmetry of a Wisconsin cornfield, corn is extraordinarily diverse. Its stalks can tower 15 feet in the air or barely break knee level. Its kernels turn out a rainbow of colors—yellow, orange, white, red, blue—and can be either grain or vegetable. But the real asset is corn’s unique structure, with its male flowers high up in the air and ears down at waist level. The separation of the sex organs makes it trivially easy to prevent corn’s natural, open pollination and instead play matchmaker. This, essentially, is what programs such as Tracy’s do, year in and year out. Using hundreds of varieties gathered from around the world, breeders cross particular plants with an eye toward enhancing desired genetic traits, or tamping down undesirable ones.
Combine handling ease with genetic diversity, and you understand why Tracy’s job is so much fun. “It’s hard not to anthropomorphize it, because really, it’s like corn wants to be bred,” he says. “We can just about pick what we want the plants to do and direct them there.” To illustrate the point, he pulls over a wooden tray stacked with dried ears from a breeding experiment. Picking a few at random, he turns the ears over in his hand and points out various kernels, some smooth and glassy, others wrinkled and opaque. “All of this variation we got by selecting for two genes,” he says. “Corn has between 25,000 and 50,000 genes, so we’re talking about an amazing amount of diversity.”
And more arises every day. When breeders select for certain traits, they create novel genetic combinations that can expose previously unseen abilities. One of Tracy’s pet projects, for example, has been to essentially reverse the evolution of sweet corn, which descended as a mutant form of dent corn, the type most commonly used to make flour and livestock feed. In a kernel of dent, the sun’s energy is converted into starch, but sweet corn carries a gene that interferes with that conversion, filling its kernels instead with the sugars that give it a sweet taste. In the late 1980s, guided by little more than curiosity, Tracy began plucking off the starchiest-looking kernels he could find in his sweet corn populations and planting those. After seven generations, he had all starch and no sugar. With advances in molecular biology, his lab has now identified at least three genes altered by the experiment, potentially unearthing an entirely new genetic pathway for the production of starch in corn.
To fellow agronomy professor Natalia de Leon MS’00 PhD’02, Tracy’s experiment shows that agriculture hasn’t yet reached the summit of what it can ask corn plants to do. “It’s just an amazing species. If you do selection appropriately, there are very few things that you cannot change in a corn plant,” she says.
But de Leon has her own poster children for corn’s genetic flexibility, an odd collection of plants that grows in a small square on her research fields. Fat with leaves and branches, they look more like bushes than corn stalks. But then you see the ears—in some cases, as many as 20 per stalk.
Known as Golden Glow, the plants are the offspring of an experiment begun in 1971 by CALS agronomist John Lonnquist, who wanted to convince farmers that corn plants with many small ears could yield as much grain than the ones we’re used to seeing, which have one or two large ears dangling from a central stalk. Beginning with a plot of ordinary field corn, Lonnquist picked plants with the most ears and crossbred those generation after generation. Lonnquist handed the project to Jim Coors, another agronomy professor, who assigned maintenance of the crop to de Leon when she was a graduate student. In 2006, de Leon returned to CALS to take over her mentor’s breeding program—the only public program in the nation that focuses on silage—and she re-inherited the Golden Glow project. Now in their 33rd generation, the plants are showing a prolificacy that few people believed corn possessed. But many farmers remain skeptical, says de Leon. “To them, it doesn’t look like corn is supposed to look. It’s just not right.”
The booming biofuels business might change their minds. Golden Glow’s ample branches create more space for leaves and tillers, which may eventually supplant kernels as the prime feedstock for ethanol. One of de Leon’s graduate students, Candy Hansey, is searching for the genes that control tiller growth in hopes of stimulating corn plants to produce more green matter without affecting their grain yield. “If we can increase the number of leaves and the width of the leaves, we can have more area for the sun to hit and bring more energy in,” says Hansey. “Energy in means energy out for biofuels.” Other breeders are beginning to experiment with corn that grows no ears at all, the theory being that corn’s leaves might be valuable enough to grow on their own as an energy crop, regardless of grain.
“The overall idea,” says de Leon, “is that maybe we have to start thinking about corn in different ways, not just the typical single stalk, annual system that we know. Maybe we can make the plants look different and do different things.”
It’s striking to note that Golden Glow’s strongest resemblance is not to corn, but to teosinte, the wild grass from which corn evolved some 7,000 years ago. Like Golden Glow, teosinte plants have several tall branches that hold small pods of kernels. The similarities are so apparent that when de Leon showed pictures of Golden Glow at a recent meeting of corn geneticists, a few scientists in the audience suggested that her plants must somehow have been pollinated by corn’s ancient ancestor.
Genetics professor John Doebley, who has studied the evolution of teosinte to corn, says there’s good reason for the likeness. “In a sense, what (de Leon’s team) is doing is undomesticating corn,” he says. In less than a human lifetime, they’ve successfully undone a shape and stature farmers have refined over several millennia.
It’s not hard to understand why farmers wanted corn to look the way it does. In the days before mechanical harvesting, who would have wanted to pluck 50 ears from every plant? Teosinte had other problems, too. Although its seeds were nourishing, they were encased in hard shells, which had to be cracked open to get to the edible parts. And they tended to fall all over the place, meaning someone had to go pick them up off the ground to get dinner. Whenever a more appealing mutant appeared—the odd kernel that developed a softer shell, or perhaps a plant that grew larger ears—its seeds were saved and replanted. And so the human conquest of corn began.
By favoring certain seeds, early farmers carved out a subset of genes that fit their needs. But needs change. We no longer harvest by hand, and so breeding for large, easy-to-grab ears may not be as important any more. (In fact, it may be disadvantageous to the plant’s health by concentrating disease and pest risk into a small number of ears.) But the intriguing possibility is that we can go backward, using ancient gene reserves to restore traits that may have been bred out of corn through past selections. “There’s no reason to believe that those ancient people got all the good stuff out of teosinte,” says Doebley. “There is likely still some good stuff in there that modern breeders may be able to identify and transfer into the corn plant.”
One example that has caught the attention of the sustainable-agriculture community is perennial corn. Domesticated corn requires annual replanting, which can be an expensive proposition if you’re fueling a diesel tractor to plant a few hundred acres each spring. The alluring possibility of self-regenerating corn dawned in 1978, when a Mexican botany student named Rafael Guzmán stumbled across a field of perennial teosinte, which was believed to be extinct. He sent a few seeds to UW-Madison botanist Hugh Iltis, who with Doebley, then his graduate student, confirmed Guzmán’s find—and realized something better still. The wild plant had the same number of chromosomes as Zea mays, which meant it could be mated with modern corn.
So far, the discovery has created more flash than fire. Although breeders have successfully bred perennialism into corn, the resulting hybrids inherit teosinte’s love of tropical climates, making them impractical for the harsh winters of the Corn Belt. Because perennial plants siphon off some of their energy building root structures to survive winter, perennial corn is also not likely to approach the yield of annual varieties. Yet the idea remains compelling. If it did emerge as a viable option, perennial corn might save hundreds of millions of dollars in fuel costs and eliminate the need for soil-eroding tillage.
But branches and roots weren’t the only losses from corn’s domestication. A more recent victim is corn’s nutritional portfolio. While its kernels have always been rich in starches and sugars, older varieties boasted a richer mix of oils and proteins than is typical today. If you doubt this, try biting into a fresh ear of field corn. What you’ll taste is the chalky sensation of near-pure starch, which makes up three quarters of the weight of a standard modern corn kernel.
You’re also tasting the dominant role of yield in modern corn farming. From a corn plant’s view, it’s more efficient to turn sunlight into starch than it is to make oils or protein, which require more energy to produce. So if you’re looking to stockpile as much energy as possible in the form of digestible food, starchy corn is the way to go. This pursuit of the highest yield has turned corn into “more of a pure carbohydrate-producer now,” says Walter Goldstein, who researches corn at the Michael Fields Agricultural Institute in East Troy, Wis. “It’s lost a lot of its protein and oil content and a lot of its flavors. If you taste some of the old varieties, they have rich perfumey tastes and deep flavors. Those just aren’t there anymore.”
For most of the past two decades, Goldstein has been working to restore those lost qualities. On a patchwork of research plots down a country road from the institute’s offices, he grows corn that differs from industrial varieties in several ways. For one thing, he eschews chemical herbicides and poesticidies, fitting with the institute’s mission to promote organic agriculture. But Goldstein’s corn is also far richer in protein, in some cases nearly double the amount in standard corn. By going back to older varieties that contain a key gene for protein synthesis, Goldstein has bred strains of corn that have significantly elevated levels of lysine and other essential amino acids. Some of the seeds are so choked with carotenoids, the orange pigments that protect eyesight and boost immune function, that they look like candy corn.
One can argue that humans have a wealth of options for eating protein, especially if they live in developed countries where meat is plentiful. But protein-rich corn may have other uses. Organic poultry producers, for example, are clamoring for a natural source of methionine, a protein that promotes egg development in chickens. Most farmers now add synthetic methionine to their chickens’ corn feed, but the National Organic Standards Board has ordered an end to that practice by 2010. Goldstein is leading a group of nearly a dozen researchers scrambling to perfect methionine-rich corn as an alternative.
On one level, results have been encouraging. In just three generations, the researchers have boosted corn’s methionine content by 75 percent, plenty sufficient to meet farmers’ needs. The problem is yield. As often happens when breeders ramp up a particular genetic trait, the plant’s energy needs change and overall production suffers. At this point, Goldstein estimates that his best high-methionine hybrids yield about 80 to 90 percent of normal organic corn.
Goldstein is confident that crossbreeding his plants with higher-yielding varieties will narrow the gap. If he can, he estimates the immediate demand from poultry producers alone would call for 5 to 8 million bushels of high-methionine corn, requiring as many as 60,000 acres to grow.
True, 60,000 acres—a little larger than the city of Madison—won’t put a dent in the dominance of dent corn. But it could add something not much seen in the U.S. corn industry: alternatives. With a few exceptions—sweet corn being the most obvious—the market regards corn as corn. Unlike apples or potatoes, where honey crisps and russets occupy their own niches, corn is generally aggregated into a few large heaps, whether it’s headed for a gas tank or a tortilla chip.
That fact has always surprised Joe Lauer, an agronomy professor and CALS’ chief extension specialist on corn. “There’s always been talk of identity-preserved marketing channels, but it has never happened,” he says. And when the market won’t pay for higher quality corn, he says farmers really only have one choice: Grow as much of it as humanly possible.
“Yield is how farmers get their raises,” Lauer says. “You can grow high-protein corn, but the market has to be willing to pay a premium for that corn. Otherwise farmers aren’t going to accept those lower yields.”
That may sound like pessimism, but it’s the hard reality that underlies the hopeful science of plant breeding. The truth is that scientists can’t change corn, at least not for long. Only society can. The genetics of corn allows us to take the plant in myriad new directions, but like the blind alleys of Don Schuster’s maze, many of them may lead nowhere. And it’s tempting, when we stumble into one of those dead ends, to blame the maze and say it’s the corn’s fault for hemming us in. But really, we know it’s the path we chose.This article was posted in Agriculture, Cover Story, Fall 2008, Features, Food Systems, Main feature and tagged Corn, Farming, Food crops, Plant breeding and genetics.