Potato breeder MSU is developing a new genetically modified potato

The Kal91.3 potato can be stored at low temperatures for a long time and produces healthier, higher quality chips.

EAST LANSING, Mich. — A new genetically engineered potato, developed by Michigan State University potato breeder Dave Douches, has been granted an exemption from biotechnology regulations for genetically modified products by the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (USDA APHIS).

The Kal91.3 potato is bred from an MSU potato variety called Kalkaska. The newly developed potato can be stored at low temperatures for a long time without sucrose, the compound in which sugar is usually stored in potatoes and converted into reducing sugars such as fructose and glucose. Without as many reducing sugars, abnormal browning and caramelization in the Kal91.3 potato can be minimized, leading to healthier and better quality products, including chips.

The Kal91.3 potato can also reduce the environmental impact of the growing process without as many fertilizers and pesticides needed to maintain the potato during storage.

Dave Douches, professor in the Department of Plant, Soil and Microbial Sciences and director of the MSU Potato Breeding and Genetics Program.

Sucrose is broken down in potatoes by vacuolar acid invertase, an enzyme that is reactive to the external environment of plants, such as temperature. About a decade ago, Jiming Jiang, MSU Foundation professor in the Departments of Horticulture and Plant Biology, published findings on how to silence or suppress the gene that produces vacuolic acid invertase in potatoes.

This discovery sparked interest in Douches, a professor in the Department of Plant Soil and Microbial Sciences and director of the MSU Potato Breeding and Genetics Program, to find a way to correct the sugar imbalance that can occur in some of the commercial chip potatoes in Michigan.

“As a potato breeder at MSU, I have always felt that using biotechnology as a tool to improve potatoes would be worthwhile,” Douches said. “We have chip potatoes that work well and do their job, but I wanted to take this gene and find out if it could improve a potato that had a problem with its sugars.

“Breeding potatoes is quite a challenge because we need so many important traits, but in this case we only needed one trait to solve the problem. Using this biotech strategy, we have managed to convert a potato that was causing us problems into a potato that is now commercially valuable.”

After multiple experiments conducted between 2014 and 2015, Douches developed an RNA interference (RNAi) construct that silenced vacuolic acid invertase in Kalkaska potatoes.

From 2016-2023, Douches tested the agronomic characteristics of the Kal91.3 potato and found that it had good shape, size and specific gravity – the measurement of starch content compared to the water in the potato.

Historically, many farmers have stored shredded potatoes at or around 50 F to prevent vacuolar acid invertase from reacting to lower temperatures and converting sucrose to reducing sugars, but doing so has made potatoes more susceptible to storage rot and moisture loss. However, the Kal91.3 potato has shown the ability to be stored at 40 F while maintaining sugar balance.

“It has a double value,” Douches said. “The first is that we stabilize the sugars. The invertase shutdown slows the conversion of sucrose to fructose and glucose, stabilizing the potato’s sugar during storage. From a metabolism point of view, it calms the potato. Secondly, we benefit from being able to store the potato for longer at lower temperatures.”

In January, Douches received notification from USDA APHIS that the Kal91.3 potato was found to pose no increased risk of plant pests compared to its conventionally grown counterpart, thereby exempting it from the biotech regulations that USDA APHIS imposes on other genetically modified products. This news meant that regulators at USDA APHIS concluded that the Kal91.3 potato could have been developed differently using traditional breeding techniques.

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Research published earlier this year by Jiang and Douches details ways to edit the gene discovered to be responsible for cold-induced sweetening, the build-up of fructose and glucose in potatoes during cold storage. The technology used in that study and in the Kal91.3 potato achieve the same goal of reducing the buildup of reducing sugars, but they work differently, Douches said.

“In the Kal91.3 potato, we place the gene in a specific orientation in the DNA that tells the potato that the gene will no longer work as well as it used to – this is called silencing,” says Douches. “In Dr. Jiang, he found a way to disable part of the promoter, a part of the gene that contains information about how the gene itself should work. This leads to the same result as silence.

“His new approach is more of a gene editing approach, while my current approach is more of a genetic engineering approach.”

The Kal91.3 potato is not the first genetically engineered invertase-silencing potato to be exempt from regulation by USDA APHIS. However, according to the USDA APHIS website, it is the first genetically engineered vegetable developed by a land-grant university to be exempt from regulation.

Douches and his team are now working with Michigan potato industry leaders to evaluate the Kal91.3 potato’s potential impact on the state’s industry, particularly in the area of ​​chipping.

Michigan is the eighth largest producer of potatoes in the US, with 70% used for French fries.

Kelly Turner, executive director of the Michigan Potato Industry Commission, said the storage capacity of the Kal91.3 potato has an opportunity to further stabilize Michigan’s potato industry with a steady supply of potatoes year-round, even when fresh harvests are available. She also said that the decrease in fructose and glucose in the potato can lead to crispier, healthier and tastier chips.

In addition to the benefits it can bring to producers and consumers, the Kal91.3 potato – and others like it – can also benefit the environment and help the industry become more sustainable amid changing climate patterns, Turner said.

“Not only does the Kal91.3 potato have a high nutrient content, but it could also be grown using fewer fertilizers and pesticides, reducing the environmental risk and footprint of the potato growing process,” said Turner. “Potatoes such as Kal91.3 also offer opportunities to address changes in climate and weather patterns, allowing potatoes to be more tolerant during periods of drought and other abiotic stresses. This helps stabilize yields and ensure food security, while maintaining environmental stewardship under changing climatic conditions.”

Turner said the industry’s collaboration with MSU to advance research in areas like the Kal91.3 potato is critical to staying ahead of new developments and providing growers with the new resources needed to move forward.

“Collaborative projects between MSU and the potato industry focus on solving practical problems, such as increasing disease resistance, controlling pests and improving crop yields through genetic modifications,” said Turner. “These joint initiatives ensure that research efforts are aligned with industry needs, leading to solutions that are directly applicable to the challenges faced by potato growers and processors on the ground.”

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