Boosting cold tolerance in fruit crops

MSU scientist Guo-Qing Song is working to uncover the molecular basis for cold tolerance in a multitude of agriculturally relevant fruit crops.

Guo-Qing Song, an associate professor in the MSU Department of Horticulture, is working to breed fruit crops such as blueberries to better tolerate cold temperatures.
Guo-Qing Song, an associate professor in the MSU Department of Horticulture, is working to breed fruit crops such as blueberries to better tolerate cold temperatures.

Guo Qing SongFor deciduous fruit plants in Michigan, such as apples, berries, cherries, peaches and others that drop their leaves during winter, freezing tolerance is a critical feature. Winter injury and spring frosts are two of the state’s particularly concerning obstacles.

Guo-Qing Song, an associate professor in the Michigan State University Department of Horticulture, is working to uncover the molecular basis for cold tolerance in a multitude of agriculturally relevant fruit crops. His focus is on genes that regulate what’s known as the chilling requirement — the minimum duration of cold weather before plants will bloom.

“In the last couple of decades, we’ve seen more unstable temperature patterns all over the world,” Song said. “This is leading to out-of-season flowering for fruit trees especially, which if followed by a rapid temperature decline can be disastrous.”

That’s what happened in 2012, one of Michigan’s worst fruit growing seasons in history. The state’s fruit industry was devastated by fluctuating temperatures, primarily a spring heat wave followed shortly thereafter by a deep freeze. The unseasonably warm temperatures prompted early flowering, which was then decimated by the freeze.

More than 90% of tart cherries were lost (from 158 million pounds in 2011 to 12 million in 2012) and 85% of apples (from 980 million pounds in 2011 to 115 million in 2012).

Although early frosts have always been on the minds of growers, climate change has exacerbated the problem. Song said that in temperate European climates, the growing season has started 2.3 days earlier each decade of the past 40 years.

While cold-tolerance genes have been widely studied in model plants such as Arabidopsis, they are not well understood in many agricultural crops. Given the prominence of the blueberry industry in Michigan, which is the nation’s largest with more than 100 million pounds produced each year, Song has strived to identify varieties that show greater ability to withstand the cold. The goal is to isolate those beneficial genes for use in less-tolerant, high-yielding cultivars.

For a project published in the International Journal of Molecular Sciences, Song and a team of researchers sought to enhance the cold tolerance of a widely grown blueberry called Legacy. Using genetic engineering techniques, Song introduced a gene from a separate tolerant variety and developed new Legacy strains that are better able to withstand low temperatures.

But he noticed something else. One of the lines yielded smaller fruit and showed a lower chilling requirement.

“This is desirable for those growers in a milder climate, so this research had multiple benefits,” Song said. “We demonstrated the ability to add a gene to an important variety to make it more cold hardy, and we discovered a molecular pathway of dwarfism and lowering the chilling requirement.”

Song, who also serves as the associate director of the MSU Plant Biotechnology Resource and Outreach Center (PBROC), said sharing his research is one of the crucial aspects of his work. In addition to creating new genetic engineering strategies for specialty crops through the PBROC, Song is providing seminars to colleagues worldwide on genetic engineering and the application of biotechnology for plant breeding.

“Developing food crops that can flourish in a changing climate is vital to feeding a growing world population,” Song said. “It’s important that the global scientific community do this in a safe and sustainable way.”

This article was published in Futures, a magazine produced twice per year by Michigan State University AgBioResearch. To view past issues of Futures, visit www.futuresmagazine.msu.edu. For more information, email Holly Whetstone, editor, at whetst11@msu.edu or call 517-355-0123.

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