With global climate models projecting a temperature rise of one to four degrees by mid-century, evaporation rates will rise, and rainfall is likely to decline by a further 20 per cent across Australia's drought-ridden south-east.

These climatic trends will intersect and ramp up salt concentrations in wheatbelt soils that, in many regions, already have a toxic layer of ancient leached salt just below the root zone. Moisture and nutrients below this layer are inaccessible to the crop.

For the fortunate few blessed with low-salinity soils, high-protein durum wheat may require a little extra nitrogen to achieve the high protein levels prized by pasta manufacturers, but profits usually match or exceed those from bread wheat.

But durum varieties, which are all tetraploids, are less tolerant of salt than hexaploid bread wheats, or barley, and the sodium ions in sodium chloride cause yield depression, eroding any price advantage over bread wheat.

At CSIRO Plant Industry in Canberra, Dr Rana Munns' plant physiology research group has discovered a sodium-tolerance gene that promises to provide durum growers with genetic insurance against salinity, and which could see durum wheat plantings expand into mildly salinised regions of southern NSW, Victoria, SA and WA.

The CSIRO team owes its original discovery to veteran NSW Primary Industries durum wheat expert Dr Ray Hare, at Tamworth, home of the Australian National Durum Wheat Improvement Program.

Rana Munns and Ray Hare have been friends since they were teenagers growing up in the same suburb in Sydney.

In 1998, Munns and Hare were discussing the problem of durum's lack of salt tolerance. Hare envisaged a day when durum wheats with improved salt tolerance would be grown in moderately salinised soils across southern Australia.

Munns asked Hare to provide her with selections from the durum wheat seed bank in Tamworth. Hare took 64 of them to Canberra for screening for salt tolerance, with no foreknowledge that they would find any significant variation.

They were surprised when their tests identified several lines that actively excluded sodium ions from their roots. They had very low sodium levels in their leaf tissues.

In the early 1970s, Hare and Dante The undertook their PhD research projects at the Plant Breeding Institute at the University of Sydney. Dante The was attempting to improve the resistance to stem rust of hexaploid wheats by transferring a resistance gene from a land race of the primitive diploid wheat, einkorn (Triticum monococcum).This gene transfer was achieved via a series of crosses, firstly monococcum to tetraploid durum wheat. Then the resistant durum progeny were crossed to bread wheat.

The intermediary resistant durum lines inadvertently carried the sodium exclusion genes from the monococcum and it is these lines that have been used by CSIRO.

Einkorn wheat

Archaeologists have found 9000-year old carbonised grains of einkorn wheat in the Karacadag Mountains of Anatolia, in Turkey, confirming that Neolithic farmers domesticated einkorn wheat from a large-seeded wild grass, Triticum boeoticum, not long after the last glacial period.

Dante The successfully crossed the einkorn wheat with two rust-susceptible durum varieties, Marrocos and Glossy Hugenot.

He lodged some of his project seed lines with the durum seed bank in Tamworth, where, more than three decades later, Hare remembered them and included several among the 64 varieties to be screened by Munns' group.

Einkorn was known to be resistant to stem rust, because it was one of a dozen wheat types that pioneering US plant pathologist Professor E. C. Stakman selected for his celebrated "macroarray" of standard, rust-resistant wheat lines 75 years ago.

Stakman's "Holy 12" carry unique combinations of resistance genes. By dusting them with rust spores, breeders can assess the virulence of emergent rust strains, and whether their breeding lines will possess resistance. Einkorn was one of three primitive, diploid progenitors of today's hexaploid bread wheats.

An improbable genetic collision in a Neolithic farmer's field somewhere in the Fertile Crescent at least 6000 years ago combined the entire genomes of jointed goat grass (Triticum tauschii), a diploid, and a tetraploid spelt-like wheat (probably Triticum dicoccum), itself the product of an earlier merger between einkorn wheat and an as-yet unidentified diploid wild grass.

While the A, B and D genomes share a nucleus, and collaborate functionally, they retain their separate chromosomal identities.

When a tetraploid durum wheat is used as the female parent, and its inflorescence is dusted with pollen from diploid einkorn, their chromosome counts mismatch, leaving half of the durum chromosomes unpaired. Yet the hybrids produce viable seed - this was how The developed his einkorn/durum hybrids.