Ancient history yields answers for today

Harvesting the salt secrets of the ancient world: Rana Munns with (R) the ancient wheat race crossed with Wollaroi (in front) to make the F1 generation cross plants that exclude salt from their roots (L)

Wheat races developed in the ancient world hold the promise of tougher wheats and possibly salt-tolerant pulse crops for Australia.

Surviving on the sodic soils in what was ancient Persia, some of these ancient wheats have the ability to exclude salt from their root systems. CSIRO scientist Rana Munns and NSW Agriculture national durum wheat breeder Ray Hare have successfully transferred this ability to modern durum varieties and to breeding lines due for future release.

Growers through the GRDC are now supporting research to track down the gene or genes responsible for this trait. If that is successful, modern transgenic technology may be able to transfer salt tolerance to other crops such as the pulses, greatly improving their ability to thrive in difficult soil conditions.

Durum: no salt, thanks

Durum has always been a discriminating crop. While some bread wheat varieties, notably Janz, perform happily in soils with a high sodium content, none of our current durum varieties thrive under the same circumstances. The difference shows up in the genetic blueprint of the two crops.

Bread wheat has one more genome than durum, and this genome carries its ability to exclude salt. While all the textbooks suggested that there was no observable variation in salt tolerance in durum varieties, and so no possibility of selecting a salt-tolerant durum line, the two researchers believed otherwise. They set out to track the ancestors of modern durum back to ancient Persia.

Working with 60 ancient types, some more than 2 m tall, the two researchers identified three which showed the ability to exclude salt from their root systems. Using standard crossing techniques they transferred the trait to existing durum varieties.

Field trials and gene trails

They don't yet claim that they have salt-tolerant varieties of durum. They can't be certain of that until they can get the new crosses into production trials, but Dr Hare admits that he's confident. "I'm surprised by the progress we've made in the last 18 months," he said. "Generally you can expect something to go wrong in a breeding program, but we're still waiting."

Success of current tests will open up thousands of hectares of new country to durum production, and that could just be the start.

"We still haven't identified the gene or the genes that are responsible for the plant's ability to exclude salt," says Dr Munns. "Plants survive in sodic soils either by preventing the salt from entering their system or by isolating the salt inside the vacuoles of its cells. Our parent plants use the same technique as bread wheat varieties — they prevent the salt from entering their systems.

"Our task now is to isolate the gene responsible for the trait. The search is on for the molecular marker that will pinpoint the gene."

Dr Munns says that if this can be done then there is no reason why the gene can't be transferred into other crop plants, "particularly some of the pulse crops whose inability to deal with sodic soils is a problem".

Program 1.6.2

Contact: Dr Ray Hare 02 6763 1100 or Dr Rana Munns 02 6246 5280