Shrinking Corn: A Win-Win for Farmers and the Environment

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On the 10th of August 2020, a historic windstorm swept across Iowa, the heart of the U.S. Corn Belt. With gusts reaching up to 225 kilometers per hour, the tempest wreaked havoc, flattening fields and structures, resulting in an estimated $12 billion in losses across multiple states. Kelly Gillespie, a crop physiologist at Bayer Crop Science, vividly recalls witnessing the devastation—houses in ruins, silos wrecked. Approximately 16% of Iowa’s corn and soybean crops suffered damage or were completely destroyed. “As far as the eye could see, corn was snapped and broken.”

However, amid this destruction, Gillespie glimpsed a ray of hope. When she and fellow researchers examined experimental corn plants developed by Bayer, they discovered that a majority of these plants had withstood the storm’s force and remained upright. The secret to their resilience? They were shorter.

To the casual observer or someone navigating a corn maze, the most striking aspect of corn is its towering height. While modern corn can grow twice the height of a person, this height brings vulnerabilities, making the plants susceptible to wind damage and more challenging for farmers to manage. Plant scientists believe that by reducing corn’s height, they can enhance its performance, a feat pursued through both conventional breeding and genetic engineering. Bayer has introduced a shorter variety in Mexico, while other companies have introduced their versions in the United States, signaling a growing interest in this endeavor.

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Experts argue that shorter corn could be a game-changer for farmers. Rex Bernardo, a corn breeder and geneticist at the University of Minnesota, remarks, “This is an idea long overdue.” Beyond fortifying wind resistance, the reduced stature enables farmers to access their fields with tractors for longer periods into the summer, allowing for late-season fertilization or fungicide application to boost yields. According to Stine Seed, a company at the forefront of short corn development, this new crop can further increase yields due to its ability to be planted more densely.

Bayer is in the final stages of its U.S. trials, conducted this summer across 12,000 hectares in Iowa and nearby states. The company plans to make the seeds available to U.S. farmers next year. Another major seed company, Corteva Agriscience, is set to follow suit with its own varieties. While Bayer’s corn was conventionally bred with the Midwest Corn Belt in mind, the company has recently created a transgenic version that can be swiftly adapted to other regions. This transgenic version received approval from the U.S. Department of Agriculture (USDA) in June, marking a significant regulatory milestone.

These new corn varieties continue a longstanding tradition of enhancing crops by reducing their size. In the 1950s and ’60s, plant breeders developed semi-dwarf versions of rice and wheat, enabling plants to bear more grain without collapsing. These high-yielding varieties played a pivotal role in the Green Revolution, averting famines in the developing world. With a better understanding of the complex interplay of genes and hormones governing corn growth, there’s a growing opportunity for corn to achieve greater heights by becoming shorter.

Corn (Zea mays) underwent significant transformation from its domestication in southern Mexico around 9,000 years ago. In comparison to modern corn, its closest living relative, a rangy wild grass called teosinte, appears untamed, with multiple stalks and tassels that mature into small cobs with just two rows of seeds. Teosinte’s seeds fall off, posing a challenge for easy harvesting, a nightmare for farmers. Some of the oldest corn cobs discovered by archaeologists are small and fragile. However, through millennia of selective breeding by Indigenous farmers and later by universities and multinational companies, corn has evolved into one of the world’s leading food crops. In the U.S., it accounts for roughly one-third of agricultural income, earning farmers $89 billion in 2022.

With success came stature. Over the last half-century, as breeders selected for larger ears with more and plumper, heavier kernels, they inadvertently chose taller plants with abundant leaves for photosynthesis and lofty stalks. While modern corn can grow up to 4 meters in height, the prevalent starchy varieties in the U.S. range from 2.5 to 3.5 meters.

However, tall plants come with inherent weaknesses. The weight of the ears, often positioned more than halfway up the stalk, renders the plant susceptible to snapping or toppling in strong winds. Reducing the height of corn isn’t the sole solution, notes Tony Vyn, an agronomist at Purdue University. Breeders have also prioritized sturdier stalks and resistance to stalk rot, which plagued earlier corn varieties, making them more prone to breaking under the weight of their grain or succumbing to windstorms.

Even so, between 2001 and 2016, around 800,000 hectares of corn fields suffered damage from high winds, according to U.S. government crop insurance claims. While this pales in comparison to the 38 million hectares affected by drought during the same period, companies view it as a compelling selling point for short corn.

Bayer has employed conventional breeding techniques to create three short hybrid varieties, which were trialed for the U.S. market this summer and are currently being harvested by approximately 300 farmers. Field trials demonstrated superior wind resistance compared to tall corn. After the 2020 windstorm, an even more rigorous test ensued. Gillespie and colleagues analyzed 14 experimental fields struck by heavy winds; on average, 25% of short corn was damaged compared to 50% of tall corn, as reported in Crop Science in August 2022.

Corteva, the parent company of Pioneer Hi-Bred International, aims to achieve similar results with its conventionally bred short corn, anticipated to hit the market in a few years. Corteva researchers assess the strength of new hybrids by subjecting them to gusts of up to 160 kilometers per hour from a wind machine.

Breeding shorter stature into an existing corn variety typically spans five years or more. In a bid to expedite this process, Bayer has turned to genetic engineering. Speed is crucial as Bayer offers roughly 200 hybrid corn varieties tailored to various conditions, including climate and disease threats. Developing shorter versions of all these varieties through conventional breeding and producing enough hybrid seed for sale would be prohibitively time-consuming.

Bayer’s genetic engineers zeroed in on a plant growth hormone called gibberellin. Initially, the approach seemed unpromising. Decades ago, researchers disabled the genes governing early stages of gibberellin production, resulting in plants with distorted flowers and abnormal ears. However, scientists adapted an approach previously employed to create shorter versions of crops like tomato, apple, and banana. They figured out how to suppress corn genes that encode enzymes known as gibberellin 20 oxidases, responsible for the final biochemical steps in hormone production in specific parts of the plant. This way, gibberellin levels can be reduced in the stalks without compromising flower development, curbing plant growth without undermining productivity.

Initial efforts produced corn plants that were excessively short for commercial viability. After extensive tinkering, Gillespie and her colleagues, in collaboration with the company BASF, overcame the challenge. They introduced DNA encoding microRNAs—small molecules capable of suppressing genes. In this instance, the targets were two genes governing gibberellin production primarily in the leaves and stalk. This resulted in plants that were one-third