RESEARCHERS at The University of Western Australia (UWA) Institute of Agriculture have confirmed that wheat varieties tolerant to iron, manganese and aluminium perform better in acidic, waterlogged soils, while varieties intolerant to such ion toxicities grow poorly and yield considerably less.
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Lead researcher Dr Hossein Saberi explained that waterlogged soils were oxygen deprived, which increased iron and manganese concentrations to toxic levels, while acidic soils had increased concentrations of aluminium ions that were also toxic to plants.
"The worst possible combination is acidic soils that undergo transient waterlogging, because in these soils plants are exposed to multiple ion toxicities," Dr Saberi said.
Funded by an Australian Research Council (ARC) Linkage Project, with support from the Department of Agriculture and Food WA, Dr Saberi and Professor Zed Rengel developed and optimised screening techniques for assessing wheat tolerance to ion toxicities, followed by characterisation of a large number of Australian wheat genotypes.
"Our project has developed the tools to test if tolerance to iron or manganese and aluminium toxicity conferred improved performance in waterlogged, acidic soils," Dr Saberi said.
InterGrain senior wheat breeder, Robin Wilson said the UWA research underpinned development of wheat varieties for their ability to cope with iron, manganese and aluminium toxicities commonly encountered in the WA grainbelt.
"The lines tested are the up-to-date material from the breeding programs and will help shape material to be released and guide us regarding what lines to continue with.
"The flow-on effects, in terms of the enhanced ability to better cope with transient waterlogging, is a great bonus," Mr Wilson said.
Recent research at UWA revealed that tolerance to multiple ion toxicities improved wheat performance during the vegetative growth stage in waterlogged acid soils and increased grain yield.
"We're now validating this breakthrough finding, which potentially has significant implications also for barley and canola, the most important grain crops after wheat in WA," Dr Saberi said.
To quantify the effect of individual ions versus combined tolerance in the same genetic background, the UWA team is pyramiding ion toxicities and producing near-isogenic lines.
"This work and concurrent activities are improving understanding of genetic and molecular aspects of the constraints and will enhance breeding of wheat cultivars tolerant to ion toxicities, thereby minimising yield losses in high rainfall areas in WA and other states," Dr Saberi said.
Professor Wallace Cowling of the UWA Institute of Agriculture, who endorsed Dr Saberi's approach to the problem, considers that multiple ion toxicities in transient waterlogged soils could account for poor growth of canola in some soils.
"Ion toxicities in waterlogged, compacted layers could account for the underperformance of canola in many high rainfall areas of southern Australia," Professor Cowling said.
With more than 2.5 million hectares of acidic soils and 1.8 million hectares of periodically waterlogged soils in WA's grainbelt, ion toxicities are major constraints to wheat yield.
In Victoria more than four million hectares of mostly duplex soils suffer from an estimated yield loss from waterlogging of 20 to 80 per cent in wheat and 50pc to 85pc in barley.
According to Professor Rengel, these waterlogging-prone areas frequently coincide with acidic soils, with acidity and waterlogging increasing concentrations of soluble aluminium, iron and manganese to toxic levels, which, in turn, constrains the yield of intolerant genotypes.
In Australia, soil acidity affects 80 - 90 million hectares of agricultural land, of which more than one third, with calcium chloride pH < 4.8, requires immediate remedial action.
