by Erik Stokstad, Science magazine
On 10 August 2020, a record-breaking windstorm raced across Iowa, the big buckle of the U.S. Corn Belt. Gusts up to 225 kilometers per hour flattened fields and buildings, with losses totaling an estimated $12 billion across several states. “It was devastating,” says Kelly Gillespie, a crop physiologist with Bayer Crop Science, who recalls driving by ruined houses and wrecked silos. About 16% of Iowa’s corn and soybean crops were damaged or destroyed. “Corn snapped and broken for as far you could see.”
In the midst of the destruction, though, Gillespie saw glimmers of hope. When she and other researchers visited fields of experimental corn plants developed by Bayer, they saw that most of the plants had resisted the force of the storm and remained standing. The source of their strength? They were shorter.
To an interstate traveler–or anyone lost in a corn maze–the most impressive feature of corn is its stature. Modern corn can grow twice as tall as a person, but height has drawbacks, making the plants vulnerable to wind and more difficult for farmers to tend. Plant scientists think corn can be improved by making it shorter, and leading seed companies are doing that through both conventional breeding and genetic engineering. Bayer has launched a short variety in Mexico, another company is selling its versions in the United States, and more are getting involved.
Researchers say short corn could be a boon for farmers. “This is an idea long overdue,” says Rex Bernardo, a corn breeder and geneticist at the University of Minnesota. “I’m quite excited.” In addition to bolstering wind resistance, the short stature will allow farmers to drive tractors into their fields longer into the summer to add late-season fertilizer or fungicides to boost the harvest. And according to Stine Seed, a company that has pioneered short corn, the new crop can increase yield even further because it can be planted more densely.
Bayer is now wrapping up its final round of U.S. trials, which took place this summer across 12,000 hectares in Iowa and three nearby states. The company plans to start selling seed to U.S. farmers next year,and at least one other large seed company, Corteva Agriscience, will soon follow suit with its own varieties. Bayer’s corn was conventionally bred with the Midwest Corn Belt in mind, but the company has recently developed a transgenic version it can quickly and efficiently tailor to other regions. In June, it was approved by the U.S. Department of Agriculture (USDA), a key regulatory step.
The new corn varieties join a long tradition of improving crops by shrinking them. In the 1950s and ’60s, plant breeders created semidwarf varieties of rice and wheat, allowing plants to bear more grain without collapsing. These high-yielding varieties were key to the Green Revolution, and they prevented famines in developing world. Now that researchers have pieced together the complex interplay of genes and hormones that control corn growth, the time may be ripe for corn, too, to go big by getting shorter.
CORN (ZEA MAYS) was a much different plant when it was domesticated in southern Mexico some 9000 years ago. Compared with modern corn, its closest living relative, a lanky wild grass called teosinte, looks disheveled, with multiple stalks and tassels that mature into many small cobs with just two rows of seeds. In what would be a nightmare for farmers, teosinte’s seeds fall off, rather than clinging to the cob for easy harvest. Some of the oldest corn cobs uncovered by archaeologists are also tiny and fragile. But after millennia of selective breeding–first by Indigenous farmers, and later in universities and multinational companies–corn has become one of the world’s dominant food crops. In the United States, it brings in about one-third of income from all crops, earning farmers $89 billion in 2022.
With success came stature. Over the past half-century, as breeders selected for larger ears with more numerous and plumper, heavier kernels, they ended up choosing big plants with many leaves for photosynthesis and tall stalks. Modern corn plants can grow up to 4 meters high, although the dominant starchy varieties in the U.S.–88% is used for livestock and ethanol–range between 2.5 and 3.5 meters.
Tall plants have an inherent weakness, however. The weight of the ears, usually more than halfway up the stalk, makes the plant vulnerable to snapping or tipping over in strong winds. Making corn shorter isn’t the only remedy, notes Tony Vyn, an agronomist at Purdue University. Breeders have also selected for stiffer stalks, as well as for resistance to stalk rot, which made earlier corn varieties more prone to snap under the weight of their grain or blow over in windstorms.
Even so, between 2001 and 2016, about 800,000 hectares of corn fields were damaged by high winds, according to U.S. government crop insurance claims. That’s not much compared with the 38 million hectares damaged by drought during the same period, but enough that companies see it as a selling point for short corn.
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