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‘Aquaporin’ genes hold key to sprouting-resistant cereal crops

Pre-harvest sprouting costs millions annually in grain quality losses, particularly in susceptible crops such as Canada Prairie Spring (CPS) wheat and malting barley.

Now a new study at the University of Saskatchewan has identified the genetic key to help prevent this problem. The answer lies in a unique set of genes, called ‘aquaporin’ genes, which control water uptake in cereals.

“Our study is the first to show that germination of seeds is strongly correlated with the uptake of water into the embryo, which is regulated by the aquaporin genes,” says Dr. Lawrence Gusta, a plant molecular biologist who led the two-year study, supported in part by Western Grains Research Foundation’s Endowment Fund.

This finding opens the door for researchers to develop varieties with aquaporin profiles that reduce the risk of pre-harvest sprouting and other moisture-related problems.

The study shows that the uptake of water into seed embryos can trigger the germination process, says Gusta. “Based on these results, the key to preventing pre-harvest sprouting is to select lines that do not produce aquaporins quickly when seeds are exposed to wet conditions. In other words, you want the plant to develop a specific degree of dormancy.”

The trick is to develop the right level of dormancy, without delaying germination, says Gusta. This is particularly important in malting barley, which requires good germination for the malting and brewing process. “Ideally, we would want a line that does not readily produce aquaporins prior to harvest, but does so several weeks after harvest.”

Researchers can immediately use the study findings to develop markers for lines that are susceptible to sprouting, says Gusta. For example, the study established a close correlation between sprouting-susceptible CPS wheat and the presence of four specific aquaporin genes.

Another important next step is to find out what factors regulate the production of aquaporins by the plant, he says. This will open more possibilities for directly regulating water uptake.

The findings may also lead to genetic solutions for a problem in stored barley called “anoxia,” he says. Anoxia is essentially a “drowning” of seeds caused by a combination of high temperatures and humidity.

“Seeds require more than 30 percent seed moisture content to successfully germinate,” explains Gusta. “When seeds are stored at temperatures warmer than 30 degrees with 85 percent relative humidity, they absorb water. However, the quantity is not sufficient to allow germination to progress and the seeds essentially drown.”

The study found that stored seeds die faster if they are exposed to pre-harvest wet conditions. As seeds start to die, they lose the ability to produce aquaporins.

Western Grains Research Foundation’s Endowment Fund has contributed over $17 million to nearly 200 crop research projects in Western Canada since its inception in 1983.

WGRF information at www.westerngrains.com

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