From bioassays to field trials: screening and selection of microbes for control of Rhizoctonia root rot on wheat

Abstract: Rhizoctonia root rot is the major fungal root disease of cereals in low to medium rainfall areas with limited chemical and agronomic control options. Disease is influenced by soil microbes and this project successfully developed and used new screening methods to allow rapid initial evaluation of microorganisms in bioassays and in the field to identify strains which are candidates for development as commercial inoculants. From 2310 strains initially assessed in a high throughput plant-pathogen-soil tube bioassay, 43 strains (1.9%) reduced disease. Of these, 21 strains had > 20% survival on seeds over 7 days and were then assessed in hand planted microplots to provide initial evidence of efficacy in the field. The eleven strains which reduced disease were then assessed in 20 m field plots. From this screening methodology, one strain was identified that increased grain yield in Rhizoctonia infested fields between 3.8 to 4.2% and performed better than current chemical controls.