EXTRACT: 'The results from these trials could be a major step forward towards salt-tolerant wheat.' - Dr Yusuf Genc, a Molecular Plant Breeding researcher based at the University of Adelaide and South Australian Research and Development Institute.

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SCIENTISTS DISCOVER HOW WHEAT CAN STICK-IT-OUT IN THE SALT
Media Release: April 11 2007 http://www.molecularplantbreeding.com/news/releases/070411.asp

It may not be quite as salt-loving as a mangrove, but scientists have discovered that wheat has more in common with the coastal dweller than anyone realised.

The Molecular Plant Breeding CRC's Dr Yusuf Genc has found that different varieties of wheat have different ways of dealing with salinity.

The research has implications for cereal breeders, who have long sought to breed varieties that are resistant to salinity.

When most people think of salinity they imagine vast and desolate tracts of land, too salty for even the hardiest crop to grow. But the conspicuous 'dryland' salinity is only part of Australia's salinity problem. Transient salinity, the seasonal movement of salt in and out of the soil profile, is not as severe, but is responsible for losses of up to $1.3 billion per year for the Australian farming economy.

Some 67% of the dryland cropping area in Australia has potential for transient salinity; and when it hits, the toxicity and resulting decrease in growth makes for meagre yields.

While no small effort has gone into the development of new salt-tolerant varieties, researchers have so far had limited success.

But with new insight into the mechanisms that wheat uses to cope with salt, breeders may soon be able to select for salt tolerance.

'People have been working on this for 50 years and guess what? There are very few varieties that have been released from breeding programs with any kind of salinity tolerance,' says Dr Genc.

According to Dr Genc, keeping the salt out is not the only coping mechanism. Rather, much like a mangrove tree, it seems that some wheat varieties take the salt up into their roots, but are less affected by it than other varieties.

"The majority of people working in this field are trying to improve the ability of the plant to exclude the salt."

"Our research has shown that keeping the salt out is not the only coping mechanism. Rather, some wheat varieties take the salt up into the plant and tolerate it."

The mechanism, known as "tissue tolerance", could result in dramatic yield increases for salinity-affected growers if it could be bred into other wheat varieties.

Genc and his team grew two wheat varieties, Berkut and Krichauff, at varying salt concentrations, and evaluated their salt uptake and grain yields.

While both are known to be good salt tolerators, they found that Berkut does not prevent the salt from entering the plant as well as Krichauff. Instead, it takes the salt in but still yields as much as Krichauff if not more.

"This was at first puzzling, because traditionally researchers thought high salt concentration meant poor ability to withstand the salt," says Genc.

"It was then that we realised there were two mechanisms at work in these wheat varieties."

Some varieties had the exclusion ability whereas other varieties had the tissue tolerance ability. Genc says that this could be the reason breeders have had such difficulty selecting for salt tolerance.

"When you test such varieties together, the relationship between salt content in the plant and salinity tolerance tends to disappear because you have different varieties with different abilities."

"Our research has shown that salt exclusion is definitely not the only mechanism at work for all varieties," he said.

Now, with a better understanding of the physiology of salt tolerance, Genc is looking to identify DNA markers, a kind of genetic 'fingerprinting', which will allow breeders to screen for salt tolerance.

With field trials planned for later this year, Genc hopes to find the same effect in the field.

'We've picked two sites. Both are saline affected sites. I really can't wait to plant this population,' he says. 'The results from these trials could be a major step forward towards salt-tolerant wheat.'

Dr Genc is a Molecular Plant Breeding CRC researcher based at the University of Adelaide and South Australian Research and Development Institute.