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Bundoora, Victoria, Australia
April 11, 2007
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. |
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