The CSIRO, together with the Waite Research Institute, has successfully engineered a new salt-tolerant wheat. Angelo Risso reports.

Andrew Crowe, a commercial farmer from the Northern NSW town of Garah, faces challenges every day out in the paddocks, from weather volatility to pest control to simply making enough profit to get by.

When Dr. Rana Munns of the CSIRO Plant Industry and durum wheat breeder Dr. Ray Hare advertised their interest in conducting a groundbreaking agronomic trial on commercial property, Crowe didn’t blink before offering his services and his acres.

“We rang [Munns] and said that we’ve got some land where we know what the sub-soil constraints are,” says Crowe. “We’re happy to have other guys come in and experiment. If you want, we can do something for you here.”

The future - salt-tolerant durum wheat that could revolutionise the way crops are grown. Photo: Francois Schnell

The scientists arrived, and in the following years completed the last steps in testing their revolutionary discovery.

Using Crowe’s land, a multi-disciplinary team led jointly by the CSIRO Plant Industry and University of Adelaide’s Waite Research Institute has successfully grown the world’s first salt-tolerant durum wheat crop.

Crowe says the success of this trial, nearly 15 years in the making, has the potential to lay the foundations for a revolution in the way crops are grown worldwide.

The results were announced in the April edition of Nature Biotechnology.

“Salinity costs Australian farmers up to $1.3 billion in lost yields annually,” says Dr. Matthew Gilliham of the Waite Research Institute, and the paper’s senior author. “Estimates determine that about 70 per cent of the wheat belt in Australia is susceptible to salinity. Through the processes of climate change this susceptibility will only worsen.”

At the same time, many genes which used to provide tolerance to unsuitable physical and chemical environmental conditions were lost due to the selective breeding practices of wheat farming.

Gilliham says that modern commercial varieties of wheat have been bred to only produce good yields in good conditions, without external selective pressures.

“There is a genetic diversity lost in modern wheats that could’ve improved yields in poor conditions.”

The development of salt-tolerant wheat has been an ongoing process, with Hare and Munns working over those 15 years to screen durum wheat lines for the ability to exclude salt from the xylem – the pipe of the plant that transports nutrients to the leaves.

When salts accumulate in the leaves they become toxic to the processes of photosynthesis, and growth stagnates. If salt could be excluded from the xylem, it would be unable to damage the leaves of the crop, encouraging plant growth.

The discovery of a wild relative of modern durum wheat called triticum monococcum, a breed that is particularly adept at this salt exclusion, enabled Gilliham and his associates at the Waite Research Institute to begin researching the specific gene responsible for this quality.

The ancestral monococcum, despite its resilience to saline, produces a low yield and is unfit for commercial crop production. This made it necessary to seek an alternative solution.

“The part of the work we were involved with here at the University of Adelaide was the location and characterization of the gene in triticum monococcum that confers this salinity tolerance trait. So after a number of years, and many tests, we identified the gene involved, and at the same time crossed the gene into a modern commercial variety of durum wheat to be put into the field for tests,” says Gilliham.

“It’s the idea of taking a gene from this ancestor and adding it to the modern version, so that you get the best of both.”

The field trials were then conducted on Crowe’s Garah property by Munns, along with CSIRO colleague Dr. Richard James.

Munns and James assessed the growth and yield of lines containing the salt tolerance gene over a few seasons in 2008 and 2009.

At various locations around the farm, ranging from no salinity to very high salinity levels, crop growth was recorded, with stunning results.

“Results were positive,” says James. “Lines with the added genome yielded in order of around 25 per cent higher than those without the gene. Importantly, there was also no yield penalty in less salty soil.”

The salinity encountered on Crowe’s farm is known as transient salinity — the accumulation of salt in soils, independent of the influence of water table processes. It is important, says James, to distinguish between this naturally occurring salinity and salinity caused by irrigation, which is a worldwide agronomic issue.

“Irrigated water often has a high salt content … which is left behind in soil to concentrate over time, further reducing water quality, plant growth, and, importantly, crop yield,” says James.

With the results of the trial made public, agronomists and farmers from all over the world have been encouraged by the CSIRO to replicate the successful wheat breed and to assist in crop growth in the developing world.

Perhaps the most significant consequence of this encouragement is, therefore, the potential it has unearthed in working to alleviate food security issues in these areas.

“There will be another two billion people on Earth by 2050, and we need to produce 70 per cent more food to feed those people,” says Gilliham.

Salinity already affects over 20 per cent of the world’s agricultural soils, and current estimates dictate that the 70 per cent target will not be met in time.

“Incremental increases in the productivity of crop growth such as the one we have produced – 25 per cent being quite substantial for salty areas – is one such approach that can help start to meet these issues,” says Gilliham. “We really need to find all kinds of avenues to increase food production.”

The salt-tolerant durum variety not only relieves food security, but also offers farmers more options for how they use their land.

“Farmers now have additional opportunities for maximizing returns by growing a premium wheat in those more saline paddocks which they may typically avoid or reserve for less valuable crops,” says James.

On the ground in Garah, Crowe says that this discovery can alleviate the pressures he is currently facing.

“We’d have the potential to grow more per hectare – our yields would increase, and we could therefore get better profits.

“Using raw plant breeding skills, these findings are absolutely milestones they take massive amounts of work. The scientists that have pursued this and kept at it for the time they have … they’re legends, really.”

The team that was involved in this study is now working on other aspects of improving abiotic stress tolerance.

“Now that we’ve found the gene that is involved in this exclusion process, we can find homologous traits in other plant varieties that could be amplified to improve salt tolerance,” says Gilliham.

The  gene has also been transferred into bread wheat and trials are ongoing.

“We hope to make further advances to improve salinity tolerances, and that’s what we’re working towards now.”