Crown rot yields to bacterium

Dr Yong Huang with barley that has been attacked by crown rot (right) versus barley protected from the fungus by the bacterium.

Crown rot losses in cereals have been significantly cut by a bacterium applied at seeding in NSW field trials.

Sydney University researchers say that, in the trials at Cowra, 92 per cent of non-treated plants carried crown rot, but where the bacteria was applied, crown rot symptoms fell to 31 per cent. This follows similar control successes in laboratory and glasshouse experiments and points to the bacteria's real potential as a practical biocontrol agent.

The research, supported by growers through the GRDC, also showed that this bacterium, Pseudomonas cepacia, has potential to control other yield-sapping fungal diseases including take-all, Rhizoctonia and Pythium.

These four diseases, estimated to cost Australian wheatgrowers alone $204 million a year in lost production, are difficult to control. No resistant cereal varieties are available and minimisation of crop damage centres on cultural practices such as rotations, tillage and removal of host material.

Dr Yong Huang said that in the trials over the past two years the bacterium was applied both as a seed coating and in water as a drench. It proved most effective as a soil drench.

"As a drench in the Cowra field trials it greatly decreased crown rot and increased grain yields" he said. "It was particularly effective in a silty loam trial and less so in a red brown earth. Its action was unaffected by the presence of the fungicide benomyl on seed."

Crown rot is a major concern in the northern and southern Australian cereal belts, whereas take-all, Rhizoctonia and Pythium cause most damage in the south and west.

The researchers, with further GRDC support, will apply the bacterium in more extensive crown rot control trials at Moree this year.

"We don't know for sure, but the bacterium probably has an antibiotic effect on the plant pathogens," Sydney University Professor of Plant Pathology, Brian Deverall said.

"Quite a few beneficial microbes, including Pseudomonas species, have been registered for control of plant diseases, in particular root diseases. Development of biocontrol techniques for plant diseases is highly favoured because of the increasing public concern of damage to the environment due to extensive application of agrochemicals," Dr Huang said.

Subprogram 2.6.2 Contact; Dr Yong Huang 02 9351 7807