ARS | Publication request: Controlling Soilborne Pathogens in Wheat Production Systems

Submitted to: Washington State University College of Agriculture and Home Economics
Publication Type: Abstract Only
Publication Acceptance Date: August 20, 2008
Publication Date: August 20, 2008
Citation: Okubara, P.A., Schroeder, K.L., Paulitz, T.C., Steber, C.M., Kidwell, K. 2008. Controlling Soilborne Pathogens in Wheat Production Systems. Washington State University College of Agriculture and Home Economics. Page 37.

Technical Abstract: Pacific Northwest (PNW) wheat, barley, legume and canola varieties are susceptible to broad host-range soilborne pathogens that cause Rhizoctonia root rot and Pythium root rot. Controlling Rhizoctonia and Pythium will likely require multiple strategies. My laboratory focuses on three research areas: 1) identifying the Rhizoctonia and Pythium that occur in PNW cereal production systems, 2) identifying and characterizing resistance genes, and 3) utilizing plant genes that enhance biocontrol agents. We have used advanced DNA-based (real-time PCR) assays to show that R. solani AG-8 and R. oryzae grp III are associated with root rot of wheat, whereas R. solani AG-2-1 and AG-10 are pathogenic to legumes and canola. The Rhizoctonia occur primarily in low to moderate rainfall zones, in contrast to Pythium species, which favor high rainfall or irrigated regions. The BarocyclerTM has proven to be an important innovation for the detection of Rhizoctonia in soil samples, because high pressure is needed to extract its DNA. Until the generation of the Rhizoctonia resistant wheat genotype Scarlet-Rz1 by mutagenesis, non-GMO resistance to root diseases has been elusive. The resistance in Scarlet-Rz1 is readily deployable by wheat breeders, making it unique. Field trials are in progress to evaluate the performance of this promising new wheat. The mutagenesis approach can be used to generate Rhizoctonia resistant canola. Finally, soil bacteria of the genus Pseudomonas exert biological control of Rhizoctonia and Pythium. We have found that PNW wheat cultivars vary in their ability to support high populations of biocontrol bacteria and to accumulate disease-suppressive compounds on their roots. Current research is showing that biocontrol strains of Pseudomonas induce defense gene expression in wheat roots, possibly bolstering pathogen defenses.