The researchers inserted a gene to remove salt — in the form of sodium ions — from water taken up by the plant before it reaches the leaves, where it does most damage.
The research was published in The Plant Cell this month (7 July).
High salinity reduces crop yields on irrigated land, where one-third of the world's food is produced, and in semi-arid regions such as the Middle East.
Mark Tester, a fellow at the Australian Centre for Plant Functional Genomics, and colleagues developed a GM salt-tolerant Arabidopsis thaliana plant by introducing a gene into its root that diverts sodium ions into the roots rather than the shoots.
Plants minimise this salt accumulation naturally — but the gene decreased salt levels in the shoots by up to two-thirds.
'We've used genetic modification to amplify the process, helping plants to do what they already do — but to do it much better,' says Tester.
The main challenge is applying the technique to crop plants. He says the Arabidopsis gene has already performed well in rice, and the researchers are currently analysing rice, barley and wheat plants containing their own versions of the gene.
Tester says the freely-available technology can also alter the accumulation of other chemicals, with implications for human nutrition, plant growth and phytoremediation — using plants to soak up pollutants from soil — all of which are important for developing countries.
Rowan Sage, professor of physiological plant ecology at the University of Toronto, Canada, cautiously welcomes the news, saying: 'This is a promising approach to mildly improving salinity tolerance in crops.'
'However, I am sceptical it will produce true [salt-tolerant] crops. Sodium exclusion is but one salinity tolerance mechanism. If a plant has a very strong sodium exclusion mechanism … there are costs in terms of reduced growth potential,' he says.
'One might be able to grow rice on a salty soil, but the yield may not be worth it. The big advantage will be on mildly salty soils where the yield is repressed in non-tolerant crops.'
Link to abstract in The Plant Cell.com.