A MURDOCH University research team will use carefully-applied genetic engineering to construct acid-tolerant Brazilian bugs suitable for inoculating lucerne in WA pastures.

This would significantly reduce the levels of dryland salinity on acid soils in rural southern Australia.

“By transferring the symbiotic properties of lucerne inoculants into the acid-tolerant Brazilian rhizobia, our team expects to significantly minimise the impact of ‘recharge’ - one of the major causes of salinity,” said Dr Graham O’Hara of the Centre for Rhizobium Studies in Murdoch’s Department of Biological Sciences.

This ground-breaking research is funded by an ARC (Australian Research Council) Large Grant of $231,000 over three years.

“Recharge occurs when excess water moves below the root zone of plants and into the groundwater, causing a rise in the water table,” said Dr O’Hara.

“This eventually brings salt stored in the soil to the surface, causing salinity.”

He said the main cause of recharge, however, was the replacement of perennial, deep-rooted native vegetation with the shallow-rooted annual crops and pastures used in modern agriculture.

“Lucerne originated on sandy saline soils around the Caspian Sea and thus grows better on alkaline soils,” said Dr O’Hara.

“It is the only perennial pasture legume with the capacity to overcome dryland salinity in southern Australia. One of its key properties is that it can fix nitrogen in the soil through bacteria - or rhizobia - in its root nodules.”

However WA has a unique combination of challenges.

“In many rural regions where salinity is an increasing problem, the soils are too acidic for growing lucerne because the rhizobia do not survive,” said Dr O’Hara.

“This is a serious drawback, compromising the most immediate practical solution to dryland salinity. Hence our continued research into acid-tolerant inoculants for pasture legumes.”

Dr O’Hara has been working with researchers from Agriculture WA and the Centre for Rhizobium Studies, including Associate Professor John Howieson and Dr Ravi Prakash Tiwari, to try and overcome the problem.