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Protecting world food supplies with salt-tolerant crops

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July 16, 2009

Ordinary plants struggle to grow in saline conditions while the modified plants thrive in ...

Ordinary plants struggle to grow in saline conditions while the modified plants thrive in the same conditions.

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Salt might be great with popcorn and peanuts, but it’s not so good with soil. The U.N. estimates that the world loses at least three hectares of arable land every minute because of soil salinity. Most crops simply can’t cope with too much salt. Which is why a discovery by a team at the University of Adelaide in Australia could have a profound effect on the food supplies of our future: they’ve found a way to genetically modify plants to become more salt tolerant.

Unfortunately, irrigation techniques are slowly killing plants. According to the U.N.’s Food & Agriculture Organization, of 230 million hectares of irrigated land in the world (which produce about a third of the world’s food), nearly 20% is salt affected.

In Australia where this research is taking place, over 70% of the annual wheat crop is affected by soil salinity, costing about AUD$200 million (USD$159 million). It’s a global issue, with every continent affected.

The problem starts in the use of groundwater, which is naturally higher in salts than rainwater. It’s compounded by the fact that much agriculture involves clearing of deep-rooted natives and replacing them with shallow-rooting crops, causing the water table to rise and bring more salts with it. And then drainage is often inadequate, causing a further build-up. Once inside a plant, sodium (Na+) can quickly reach toxic levels in older leaves, killing them. This then reduces photosynthesis, growth and crop yield.

Obviously, the issues causing soil salinity need to be addressed first and foremost, but the approach adopted by Professor Mark Tester’s team doesn't rely on when and if that might happen. Rather than trying to get rid of the salt, they’re training plants to cope with it better.

Using a model plant species, the researchers modified genes specifically around the plant’s water conducting pipes (xylem) so that salt is removed from the transpiration stream before it gets to the shoot. It’s basically a genetic enhancement of a natural ability plants already have.

The team is now working on transferring the process to crops like rice, wheat and barley, and claim to already have promising results with rice. The bad news is that Professor Tester believes it will be a decade before the technology is available commercially. But do we have that much time?

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