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.