Michigan State University (MSU) has developed a genetically engineered potato that can be stored for longer periods of time without browning. It has been granted an exemption from the biotechnology regulations placed on genetically modified products by the US Department of Agriculture’s Animal and Plant Health Inspection Service (USDA APHIS).
Developed by MSU potato breeder, Dave Douches, the Kal91.3 potato is bred from an existing MSU potato variety named Kalkasa.
Potatoes typically store sugar in sucrose, which converts into reducing sugars such as fructose and glucose through reaction with the temperature sensitive enzyme, vacuolar acid invertase. The Kal91.3 potato has suppressed the gene that produces vacuolar acid invertase in potatoes, minimising off-colour browning and caramelisation, and leading to healthier and higher-quality products.
It can also reduce the environmental impact of the growing process, without as many fertilisers and pesticides needed to maintain the potato during storage.
Development process
This development was based on ten year old research by MSU Horticulture and Plant Biology Professor Jiming Jiang, who published findings on suppression of the vacuolar acid invertase production gene in potatoes.
This discovery sparked interest from 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 Michigan’s commercial chipping potatoes.
“I’ve always felt as the potato breeder at MSU that using biotechnology as a tool to improve potatoes would be worthwhile,” Douches said.
“We have chipping potatoes that work well and do their job, but I wanted to take this gene and find out whether it could improve a potato that was having a problem with its sugars.
“Breeding potatoes is quite challenging because we need so many important traits to line up, but in this case, we just needed one trait to correct the problem. Using this biotech strategy, we succeeded in making a potato that was giving us problems into one that’s now commercially valuable.”
After multiple experiments carried out from 2014-2015, Douches developed an RNA interference construct that silenced vacuolar acid invertase in Kalkaska potatoes. From 2016-2023, he tested the agronomic characteristics of the Kal91.3 potato and found it had a good shape, size and specific gravity — the measurement of starch content compared to water in the potato.
Industry opportunities
Douches and his team are now working with Michigan potato industry leaders to evaluate the potential impact the Kal91.3 potato might have on the state’s industry, specifically with chipping. Michigan is the eighth largest producer of potatoes in the United States, with 70 per cent used for chips.
Historically, many farmers have stored chipping potatoes at or around 50F to avoid vacuolar acid invertase from responding to cooler temperatures and converting sucrose into reducing sugars, but doing so has left potatoes more susceptible to storage rots and moisture loss. The Kal91.3 potato, however, has shown the ability to be stored at 40F while maintaining its sugar balance.
“There’s a double value to it,” Douches said. “The first is that we stabilise the sugars. The invertase silencing slows down the conversion of sucrose into fructose and glucose, so it stabilises the potato’s sugar while in storage.
“The second is that we benefit from being able to store the potato for longer periods of time at cooler temperatures.”
Research published earlier this year from Jiang and Douches detailed ways of editing the gene discovered to be responsible for cold-induced sweetening, the buildup of fructose and glucose in potatoes while in cold storage. The technology used in that research and in the Kal91.3 potato achieve the same goal of decreasing the accumulation of reducing sugars, but they operate differently, according to Douches.
“In the Kal91.3 potato, we’re putting the gene in a specific orientation in the DNA that tells the potato the gene won’t work as well as it used to — this is what’s called silencing,” Douches said.
“In Dr. Jiang’s approach, he found a way to knock out a segment of the promoter, part of the gene that has information on how the gene itself should work. This leads to the same result as silencing.
“His new approach is more of a gene-editing approach, while my current approach is more of a genetic-engineering approach.”
In January, Douches received notice from USDA APHIS that the Kal91.3 potato proved not to pose an increased plant pest risk relative to its conventionally bred counterpart, exempting it from the biotech regulations USDA APHIS imposes on other genetically modified products.
Regulators from USDA APHIS concluded that the Kal91.3 potato could have otherwise been developed using traditional breeding techniques.
It isn’t the first genetically engineered potato with invertase silencing to be exempt from regulation by USDA APHIS. However, it’s the first genetically engineered vegetable developed by a land-grant university to be exempt from regulation.
Industry perspectives
Kelly Turner, executive director of the Michigan Potato Industry Commission, said the storage capacity of the Kal91.3 potato has a chance to further stabilise Michigan’s potato industry with a steady supply of potatoes throughout the year, even when fresh harvests aren’t available. She also said the decrease in fructose and glucose found in the potato can lead to a crispier, healthier, and tastier chip.
“Potatoes like Kal91.3 also present opportunities to address climate and weather pattern changes, helping potatoes be more tolerant during periods of drought and other abiotic stresses.
“This helps to stabilise yields and ensure food security while maintaining environmental diligence under changing climatic conditions,” said Turner.
Turner said the industry’s partnership with MSU to advance research in areas like the Kal91.3 potato is critical for staying ahead of new developments and providing growers with the novel resources needed to move forward.
“Collaborative research projects between MSU and the potato industry focus on solving practical problems, such as enhancing disease resistance, combatting pests and improving crop yields through genetic modifications,” Turner said.
“These joint initiatives ensure that research efforts are aligned with the industry's needs, leading to solutions that are directly applicable to real-world challenges faced by potato growers and processors.”
