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Purdue researcher’s short corn has far-reaching potential for growers, industry and the environment

Gurmukh (Guri) Johal is a scientist, not a teller of fairy tales. But the Purdue professor of botany and plant pathology likens his recently patented genetic mutation in corn to “Goldilocks and the Three Bears.” Like the girl’s three tries to find the perfect porridge, chair and bed, Johal tried two other mutations on his 35-year path to high-yield dwarf corn before discovering the one he says is “just right.”

“I found the Goldilocks mutation in 2020 when Covid started,” Johal says. “So we could not do research in the lab and that year could not hire anybody to work in the field. I was doing everything on my own. Then I found this mutant in the field — I’d never seen anything like it before. That was my aha moment.”

This short corn variant, D16, generates a hybrid plant optimal in both height and vigor, he says.

Johal’s focus on the mechanism of dwarfing in corn dates to 1988, when he was a postdoctoral researcher with Pioneer Hi Bred Seed Company (now Corteva). “That’s where we cloned the first gene for disease resistance ever in plants, which happened to be in corn,” he says. That particular gene was closely linked to the brachytic2 (br2) mutation, which the researchers used as a genetic marker to clone the gene for disease resistance. 

“Brachysm” refers to dwarfing in plants in which only the internode — the plant stem between two nodes from which leaves emerge — are shortened. The work sparked Johal’s interest in plant height regulation and architecture. “Definitely disease resistance is very important, but height is important as well,” he says.

A short corn variant could benefit farmers, industry and the environment. Based on its financial potential, D16 has attracted interest from several large agribusinesses, for obvious reasons: U.S. farmers plant 90 million acres of corn annually. The trait is non-GMO so can be planted worldwide and, when permitted, can be easily introduced into any elite line by gene editing.

“This trait has the potential to impact the entire crop of corn in the U.S. and beyond,” Johal says.

In working toward D16, his research increased understanding of two other corn-dwarfing mutations. In 1995 he began working with anther ear 1 (an1), a gene in the same pathway that rice and wheat breeders, including Norman Borlaug, used to make dwarf varieties in the 1960s. These were key to the Green Revolution of the late 1960s, heading off famine on the Indian subcontinent and in Southeast Asia.

But corn isn’t like rice and wheat, Johal explains. “In the 1960s when people were working on rice and wheat and were very successful there, people did try it on corn. But they did not find anything that was just right, so they kind of gave up on it.”

Johal’s own research with an1 resulted in dwarf corn, but of variable height. He showed that the mechanism that worked in wheat and rice — a limitation in the pathway that leads to the production of the plant hormone gibberellic acid — didn’t work in corn because it impacted the differentiation of male and female sexes of flowers.

Johal next focused on the brachytic2 (br2) mutation of maize. Although br2 was first identified in 1951, scientists did not understand its underlying genetic mechanism until Johal and his research team published their results in the journal Science in 2003. “We showed why plants that had the brachytic2 mutation were short,” he says.

Johal’s team cloned and patented the br2 gene in 2002 in collaboration with Pioneer. Once the patent expired, other companies began applying the brachytic2 mutation to reduce the height and generate what they called smart, or short, corn.

But plant breeders didn’t get it just right, either. “Corn, unlike all other plant species, has two aspects of plant height,” Johal explains. “One is the overall height. The second is the height of the ear.” These seemed to conflict with each other, he adds: Shortening the overall plant height lowers the ear too far; bringing the ear up mitigates against the short stature of the plant.

“Working with these mutations, it became clear to me that the only way we can generate short corn plants that would be commercially viable and very beneficial, would be if the mutation were dominant, so it has to be in only one of the two inbred lines used to make hybrid plants,” Johal says. “And secondly, it has to make a plant not too tall and not too short. But that window  of height range is very narrow.”

His D16 mutant reduces corn from 9-10 feet in height to 6.5-7 feet, which keeps the ear at a height that can be harvested mechanically with a standard U.S. combine.

Since the 1960s, corn breeders have increased yield by developing germplasm that allows plants to be grown closer together. “Some people think there’s still potential to increase density,” Johal says. “But to be able to realize that potential, we first must bring the height of the plant down. Tall and dense plants become vulnerable to wind damage. This domino effect basically causes the entire crop to fall down.”

Short corn’s durability in wind is especially important as climate change increases the frequency of high-speed Midwest storms called derechos. In 2020, a derecho flattened 2 million acres of corn in Iowa alone, causing $8 billion in damage. Growers lost not just their crops; costly inputs like fertilizer, fungicide and water all went to waste.

Financial impact and environmental impact “go hand in hand,” Johal says. He cites fertilizer as an example. Normal hybrids get so tall so quickly that farmers have to provide fertilizer at the time of planting, he notes. “But plants use very little of it early on; they need it later.” In the meantime, much of the fertilizer runs off or degrades. “If farmers can provide this crop fertilizer at later stages, we would need less fertilizer,” he says.

The D16 mutation offers this possibility, he says. And because dwarf corn allows for more plants per acre, Johal believes it may allow growers to use less land, which means less energy, fertilizer, water and other expenses.

He cites a hypothetical situation: “If you have 1,000 acres of land — but only 300 acres of that land is really the best for planting — only use that much. Put your best genetics in there and give it the utmost attention and treatment, then you probably can get more from those 300 acres than the entire 1,000 acres. So then 700 acres can be left to nature.”

When Johal drives through current cornfields he envisions that balance of agricultural crops and nature — fields interspersed with forested land, especially in low-lying areas, and all the benefits of more trees, including wildlife habitat and carbon dioxide capture.

And when you come to a rural intersection in Indiana, he notes, you’ll be able to see around the short corn.

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