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Dont pass the salt

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					    Don’t pass the salt



                   CSIRO researchers, with collaborators around Australia, are taking multiple
                   approaches to improving the salt tolerance of wheat.




Salinity is a significant problem for Australian
farmers, requiring a range of approaches and
solutions.

One useful tool is salt tolerant crops, which give
farmers trying to remediate salt affected land a
source of income as well as helping to stabilise
soil from wind and water erosion.

A research team from CSIRO Plant Industry,
led by Dr Rana Munns, is looking closely at the
mechanisms of salt tolerance in wheat, with the
aim of breeding wheats tolerant of highly saline
soils.

The premium pasta wheat
Durum wheat, which attracts a premium price
for its excellent pasta qualities, is much less salt
tolerant than bread wheat.

In 2002 the project team bred the world’s first
salt-tolerant durum wheat line. The team has
now isolated two new salt tolerance genes for
use in breeding.

The two genes, Nax1 and Nax2, were derived                 Dr Rana Munns with the ancient wheat ancestor.
from an ancient wheat ancestor, Triticum               Adelaide in South Australia, showed there was
monococcum. The two genes both work by                 a yield penalty associated with genes brought
excluding salt, but from different parts of the        into the wheat from the wild relative.
plant. The first gene works by excluding salt
from the plant roots while the second excludes         Plant breeders at the CSIRO have managed to
it from the leaves.                                    overcome this problem and the latest wheats
                                                       are performing well in terms of both yield and
By using molecular markers to select for the           salt tolerance.
two salt exclusion genes, the team was able to
breed durum wheat as tolerant of salt as bread         The project team has now transferred the two
wheats. Three patents for the work are now in          new genes into bread wheat to further improve
place.                                                 its salt tolerance.

Initial field trials, conducted with the assistance    Plant breeding is a long and complex process
of Ray Hare, NSW Department of Primary                 however and commercial varieties of both salt-
Industries in northern NSW and Tony Rathjen,           tolerant durum and bread wheats are at least
from the Waite Campus at the University of             three years away.
Tackling high salinity                                A combined approach
While bread wheat and the new durum lines will        The salt-tolerant wheat project is a good
tolerate moderately saline soils, the long term       example of the different innovative ways by
aim for CSIRO is to develop wheats as salt            which plant breeders can approach a desirable
tolerant as barley.                                   outcome such as salt tolerance.

Barley can cope with highly saline soils, but         It also shows the importance of collaboration in
uses a different mechanism to the salt tolerance      such projects, as the skills and capabilities of a
genes Dr Munns and her team have identified.          wide range of researchers and organisations
                                                      across Australia are vital to the project’s wide-
Rather than excluding salt, barley segregates it      ranging success.
within the plant. The plant uses the segregated
salt to balance the pressure from the salt in the     The research is a collaborative project between
soil.                                                 the CSIRO, the New South Wales Department
                                                      of Primary Industries, the University of
Unfortunately simple molecular approaches to          Adelaide, the University of Western Australia
breeding the mechanism into wheat are unlikely        and the Australian Centre for Plant Functional
to be useful as there are many genes involved.        Genomics, with support from the Grains
It is possible, however, to select for wheats that    Research and Development Corporation
are better at this type of salt tolerance, enabling   (GRDC) and the CRC for Plant-based
CSIRO plant breeders to use classical selection       Management of Dryland Salinity.
techniques and plant breeding.
                                                      References
Hybrids for salt tolerance




                                                                                                               CSIRO Plant Industry 2008
                                                      James, R.A., Davenport, R.J. and Munns, R. (2006)
                                                                                                         +
                                                      Physiological characterization of two genes for Na
A third plan of attack is the result of pioneering    exclusion in durum wheat, Nax1 and Nax2
work by Tim Colmer from the University of             Plant Physiology 142: 1537-154
Western Australia and meticulous                      Huang, S., Spielmeyer, W., Lagudah, E.S., James, R.J.
hybridisations made by Dr Rafiq Islam from the        Platten, J.D., Dennis, E.S. and Munns, R. (2006)
University of Adelaide. By using advanced             A sodium transporter (HKT7) Is a candidate for Nax1, a
genetic techniques and a great deal of                gene for salt tolerance in durum wheat
                                                      Plant Physiology 142: 1718-1727
patience, Rafiq has managed to cross
Australian wheat cultivars with the halophyte         Byrt, C.S., Platten, J.D., Spielmeyer, W., James, R.J.
sea barley grass, creating a new hybrid plant.        Lagudah, E.S., Dennis, E.S., Tester, M. and Munns, R.
                                                                                                          +
                                                      (2007) KT1;5- like cation transporters linked to Na
After further selection, the plants should be able    exclusion loci in wheat, Nax2 and Kna1
                                                      Plant Physiology 143: 1918-1928
to withstand very high levels of salt, while the
quality of the grain should be very suitable for
stock feed.

				
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