The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (USDA APHIS) has granted an exemption from the biotechnology regulations placed on genetically modified products for a new genetically engineered potato developed by David Douches, a potato breeder at Michigan State University.

The MSU potato variety Kalkaska is the ancestor of the Kal91.3 potato. Long durations of cold storage are possible for the newly created potato without sucrose, which is the molecule that sugar usually stores in potatoes and converts to reducing sugars like fructose and glucose. The Kal91.3 potato has less off-color browning and caramelization than other varieties, which can result in healthier and better-quality goods, including potato chips.

Additionally, the Kal91.3 potato can lessen the growing process’s negative environmental effects by requiring fewer pesticides and fertilizers to keep the potato healthy throughout storage.

“Sucrose is broken down in potatoes by vacuolar acid invertase, an enzyme reactive to the external environment of plants – such as temperature,” according to a recent MSU press release.

Jiming Jiang, an MSU Foundation Professor in the Horticulture and Plant Biology departments, released research about ten years ago on how to quiet, or suppress, the gene in potatoes that makes vacuolar acid invertase. Douches, a professor in the Department of Plant Soil and Microbial Sciences and the director of the MSU Potato Breeding and Genetics Program, became interested in this discovery and set out to find a solution to address the sugar imbalance that occasionally arises in some commercial chipped potatoes in Michigan.

“I’ve always felt as the potato breeder at MSU that using biotechnology as a tool to improve potatoes would be worthwhile. 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 need 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,” Douches said.

Douches created an RNA interference (RNAi) construct that inhibited vacuolar acid invertase in Kalkaska potatoes following several trials conducted in 2014–2015. Douches evaluated the Kal91.3 potato’s agronomic traits from 2016 to 2023 and discovered that it had good size, shape, and specific gravity – the measurement of starch content compared to water in the potato.

Historically, many farmers have stored chipping potatoes at or around 50 F 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 40 F while maintaining its sugar balance.

“There’s a double value to it. The first is that we stabilize the sugars. The invertase silencing slows down the conversion of sucrose into fructose and glucose, so it stabilizes the potato’s sugar while in storage. It’s settling the potato down from a metabolism point of view. The second is that we benefit from being able to store the potato for longer periods at cooler temperatures,” Douches added.

Douches obtained notice from USDA APHIS in January 2024 that the Kal91.3 potato did not pose a greater plant pest risk when compared to its conventionally cultivated cousin, therefore exempting it from the biotech requirements imposed by USDA APHIS on other genetically modified items. This news led USDA APHIS investigators to decide that the Kal91.3 potato may have been generated using traditional breeding methods.