Suppression of Rhizoctonia solani anastomosis group 8 in Australia and its biological nature

Abstract

The nature of suppression in a field soil showing a decline in the Rhizoctonia barepatch disease of wheat (causal agent Rhizoctonia solani AG-8), in a minimum tillage system in southern Australia was investigated. The suppressive characteristics of the soil could be transferred to an autoclaved or pasteurized soil by adding 10% (w/w) of the unsterilised soil. This resulted in less disease following inoculation with R. solani AG-8. No transfer of suppression was observed when non-suppressive soil from an adjacent trial was added to the autoclaved or pasteurised soil. Gamma irradiation or pasteurisation at 60, 70 or 80 degrees C for 30 min eliminated both the ability of the soil to suppress disease and also differences in the soil microflora of suppressive soil and non-suppressive soil observed in untreated or 50 degrees C steam pasteurised soils. This is the first report of biologically-based suppression of this root rotting disease of wheat caused by R. solani AG-8.