Hybrid wheat is worth its salt on irrigated land

Hybrid wheat could resist the salty consequences of irrigation. For the first time, a team has created a salt-tolerant strain of wheat that raises yields on salt-damaged fields under real growing conditions. Previous attempts have failed to pass the hurdle of field trials.

The gene responsible for the new strain's salt tolerance, taken from an ancient ancestor of modern wheat, may help other crops.

Salt is a growing problem on the irrigated land that is a substrate to 30 per cent of the world's food. That's because irrigation water can deposit additional salt directly in soil, and leach it up from deep deposits. Grain crops fail to thrive because sodium in soil water is carried from roots to leaves, inhibiting the photosynthesis needed to make grain.

As a result, major growers in semi-arid countries around the world that use irrigation, such as Australia, are losing an estimated $12 billion a year.

Researchers have tried for years to produce salt-tolerant grain varieties, but while some have shown promise in the lab they have failed to deliver under real farm conditions.

Ancient wheat

Matthew Gilliham at the University of Adelaide, Australia, and his colleagues discovered that when the einkorn wheat ? an ancestor of modern wheat ? is grown in salty water, less sodium makes it to its leaves than in other strains.

They tracked this to a gene for a cellular pump that pulls sodium out of water headed for the leaves and sequesters it in root cells, where, according to Gilliham, it does much less damage.

The team crossed Einkorn with modern durum wheat ? the kind used to make pasta ? to introduce the pump gene without genetic engineering. The offspring did not lose yield compared with durum wheat on normal soils. This is important as most salt-affected fields have less-affected areas. On salty soils the hybrid wheat performed better than ordinary durum: it had lower leaf sodium and produced 24 per cent more grain.

Bread wheat is naturally more salt-tolerant, but early evidence indicates that adding the einkorn pump helps it, too. Having isolated the gene, says Gilliham, they can now try putting it in other crop plants as well, using genetic engineering.

"It took 15 years to develop this wheat without using genetic engineering," he says. Growing demand for food means global food production must roughly double by 2050, he says. "We can't wait another 15 years for every improvement," he says.

Journal reference: Nature Biotechnology, DOI: 10.1038/nbt.2120

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