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Lumen Winter 2007 Issue
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Research worth its salt

Soil salinity is costing Australian farmers $70 million every year in lost grain production and there are estimates that salt-affected areas could triple by 2050 to 17 million hectares, with much of that in the wheatbelt. University of Adelaide researchers at the Australian Centre for Plant Functional Genomics are working on solutions-with some promising results.

Rice plants growing in a glasshouse at the University of Adelaide's Waite Campus may hold one of the answers to Australian agriculture's growing salinity problem.

Some of this rice contains a gene which significantly reduces salt movement from the roots into the plant's leaves-where salt does most damage to a plant and affects grain yields.

One of the most exciting and novel aspects of this new salt-tolerant rice is that the gene responsible has been activated only in specific cell-types (xylem parenchyma) found in the middle of the root alongside the plants' water-carrying vessels, rather than throughout the plant.

Researcher Darren Plett explains: "I'm using cutting-edge molecular genetic techniques to express genes that we know are involved in transporting salt in plants only in specific cell types within the rice root.

"Traditionally when genes-of-interest are introduced into a plant genome, they are being switched on in every cell of that plant. We are introducing these genes so they are activated only in specific cells.

"I have found that expressing this salt transporter gene in this focused manner significantly reduces the amount of salt transported to the leaves in rice, producing lower levels of salt in the leaves than in plants with the gene expressed in all cells."

Rice, while also an important food crop worldwide, is used as a model for genetic research in cereals because of its much simpler genome and its relationship to the important commercial cereal crops, wheat and barley.

With success in producing salt-tolerant rice, the next step for the research team will be working with these genes in wheat and barley.

Mr Plett is a PhD student working with a team of University of Adelaide researchers at the Australian Centre for Plant Functional Genomics (ACPFG) where researchers are working to improve the resistance of wheat and barley to hostile environmental conditions such as drought, salinity and frost, using functional genomics technologies.

Overseen by Professor Mark Tester, Australian Research Council Federation Fellow and Mr Plett's supervisor, the 'Salt Focus Group' is taking three main approaches to developing varieties more tolerant to salt.

Under the 'forward genetic' approach using conventional breeding techniques, varieties of wild and cultivated cereal plants growing in salty conditions around the world are crossed with commercial crop plants to produce salt-tolerant, high-yielding varieties. The genes producing the salt tolerance can be identified using this technique.

The 'reverse genetic' approach involves genetic modification of crop plants to express genes thought to contribute to salt tolerance.

Under the 'molecular genetic' approach, which includes Mr Plett's research, candidate genes are inserted into a plant in such a way that they are only turned on in one tissue or under certain conditions.

Professor Tester said: "This work by Darren is central to the group moving this research from laboratory plants to commercial crops. Darren's research has tested these intellectual concepts on a crop plant-rice. It will help us make important strategic decisions about the transfer of this technology into wheat and barley."

Mr Plett grew up on a farm near Winnipeg, Canada, completing a BSc (Agriculture) and Master of Science at the University of Manitoba.

He won an Endeavour International Postgraduate Research Scholarship and started his PhD with Professor Tester in 2004, the first six months based in Montpellier, France, where the group has a collaboration. He finishes his PhD in August and will then take up a postdoctoral position at the ACPFG.■

STORY ROBYN MILLS

Darren Plett
PHOTO CHRIS TONKIN

Darren Plett
PHOTO CHRIS TONKIN

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