Grain Biotech gets OK for trial of salt-tolerant wheat

The Office of the Gene Technology Regulator (OGTR) has approved an application by Western Australian wheat breeding company Grain Biotech Australia to field-trial two genetically modified salt-tolerant wheat lines.

Grain Biotech plans to field-test the two GM wheat lines under controlled conditions on a salinised 0.45 hectare site near Corrigin this winter, to evaluate their salt tolerance and agronomic performance. The test crop is being planted this month, and the trial will continue until next January.

Under glasshouse conditions, the Grain Biotech lines -- both hexaploid bread wheats -- thrive at a salt concentration of 150 millimoles, equivalent to 30 per cent seawater.

The GM wheats contain two transgenes -- the cah marker gene, which codes for an enzyme that confers resistance to the herbicide cyanamide, used to select transformed cells in tissue culture, and the ornithine aminotransferase (OAT) gene from Arabidopsis.

The OAT gene is expressed in Grain Biotech's GM wheats at around three times the normal concentration.

In the 1990s, Canadian researchers found that tomato lines over-expressing the OAT transgene could grow and fruit in salt concentrations equivalent to 40 per cent seawater.

The gene is a component of the metabolic pathway that synthesises the amino acid proline. Proline has osmoprotectant properties -- at high concentrations in plant cells, it inhibits the loss of water from the cells in opposition to the osmotic gradient created by high salt concentrations in the external environment.

The OAT gene also confers resistance to other forms of environmental stress, including drought and frost.

Large areas of Western Australia's wheat belt are affected by rising, saline water tables. On their glasshouse performance, the company has predicted that the new GM wheats should be able to grow at lower elevations around saline seeps and lakes than barley, the most salt-tolerant of the major cereal crops.

In addition to bringing moderately salinised farmland back into production, the new salt-tolerant wheats could also help stabilise rising water tables by increasing evapotranspiration during winter.

After reviewing the company's risk assessment and risk management plan, the OGTR concluded that the limited, single-season trial would not pose any significant risks to human health and safety, or to the environment, arising from the genetic modification.

The OGTR said the GM wheats were unlikely to prove more toxic or allergenic to humans or other organisms than conventional wheat -- around 5 per cent of the population is already allergic to the gluten proteins in bread wheat.

The regulator said the herbicide cyanamide is not used in Australia, so wheat plants carrying the cyanamide-resistance gene are unlikely to be at a selective advantage in the Australian environment.

In any case, cyanamide is rapidly broken down by microbial activity in the soil, it is likely that cah enzymes (and, by implication, bacteria or fungi carrying resistance genes) are already widespread in the environment.

Anti-GM activists have repeatedly claimed that GM crops, or GM crop hybrids, could become 'superweeds'. But the OGTR said the introduction of the two transgenes was unlikely to make the wheat lines weedy. In its assessment, it noted that "The domestication of Triticum aestivum into what we now know as bread wheat resulted in the loss of most of the characteristics that contribute to successful weediness, such as competitive ability and seed heads that shatter at maturity."

Under glasshouse conditions, the GM wheats grew slightly smaller than conventional wheat. But in all other respects, their growth habit and architecture was similar -- the OGTR said it was possible that overproduction of proline may have a metabolic cost in terms of the overall fitness of the plant.