Sweet Success: Helping Stevia Plants Brave the Cold

Mar 19, 2021

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By Eric Hamilton

It’s a fact - humans love sugar. For those of us who also like to watch our calories, sugar substitutes can help.

Some zero-calorie or low-calorie sweeteners have attracted bad reputations for containing unnatural ingredients. But there are also natural sweeteners derived from plants, like stevia.
Stevia growing in the greenhouse
Stevia growing in the greenhouse at North Carolina State University. 
Stevia is hundreds of times sweeter than sugar, and it has no calories. The global stevia market is now worth hundreds of millions of dollars.
The sweetener is derived from the leaves of the plant Stevia rebaudiana, a native of Paraguay and Brazil. The leaves make chemicals similar enough to sugar to trick the tongue. But our body doesn’t burn these chemicals as fuel.
Todd Wehner is a plant breeder who aims to develop stronger varieties of stevia. These better varieties can help farmers and consumers alike.
His research was published in Agrosystems, Geosciences & Environment, a journal of the American Society of Agronomy and Crop Science Society of America.
“The market is growing rapidly as companies and consumers move away from sugar in their diet,” says Wehner.
Although this tropical plant is grown around the world, it faces hurdles growing in cold climates. Freezing temperatures can dramatically injure or even kill stevia plants in short order. That makes it harder for farmers in countries like the U.S. to grow the sweet crop.
Stevia growing in the greenhouse
A chilling chamber at the North Carolina State University Phytotron used to study cold tolerance of stevia plants. 
So, plant breeders like Wehner are interested in finding the hardiest stevia plants out there to help crops brave the cold.
“As we continue to select varieties that are cold tolerant in our area, new releases will have adaptation to a wider production region,” says Wehner.
With his teammates, Wehner recently shared findings about the cold tolerance of different stevia varieties. Their results can help scientists breed cold-hardy stevia plants better adapted to the U.S. and other temperate climates.
To find the strongest plants, the research team subjected 14 varieties of stevia to different cold stress tests. The tests ranged from just below to just above freezing. Plants were exposed to cold for anywhere from 2 to 10 days. After the stress tests, the scientists assessed how much damage the plants sustained.
A couple varieties were clear standouts in their ability to resist the cold. These varieties might be useful for breeders who want to make cold tolerant stevia crops.
The plants grew normally after being moved to warmer conditions. This allowed researchers to harvest seeds for the next generation.


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