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

A new genetically engineered potato developed by Michigan State University potato breeder Dave Douches has been granted exemption from the biotechnology regulations placed on genetically modified products by the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service.

The Kal91.3 potato is bred from an MSU potato variety named Kalkaska. The newly developed potato can be stored in cool temperatures for long periods of time without sucrose, the compound that sugar is typically stored in potatoes as, converting into reducing sugars such as fructose and glucose. Without as many reducing sugars, off-color browning and caramelization can be minimized in the Kal91.3 potato, leading to healthier and higher-quality products, including potato 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.

Sucrose is broken down in potatoes by vacuolar acid invertase, an enzyme reactive to the external environment of plants — such as temperature. Roughly 10 years ago, Jiming Jiang, an MSU Foundation Professor in the departments of Horticulture and Plant Biology, published findings on how to silence, or suppress, the gene that produces vacuolar acid invertase 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, Douches 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.

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,” Douches said. “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 of time at cooler temperatures.”

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, thus making it exempt from the biotech regulations USDA APHIS imposes on other genetically modified products. This news meant regulators from USDA APHIS concluded that the Kal91.3 potato could’ve otherwise been developed using traditional breeding techniques.

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