Submitted to: International Rhizoctonia Symposium
Publication Type: Abstract Only
Publication Acceptance Date: April 20, 2013
Publication Date: August 22, 2013
Citation: Okubara, P.A., Kogel, K., Blechl, A.E., Hulbert, S.H. 2013. Host factors governing resistance to Rhizoctonia solani. International Rhizoctonia Symposium. Abstract #10, p.31. Technical Abstract: In the state of Washington, USA, annual losses of wheat attributed to soilborne necrotrophic fungal pathogens, such as Rhizoctonia solani, are estimated to be over US$100 million, and global estimates exceed US$1 billion. Host genetic resistance is a sustainable means of disease control that can be deployed in small- or large-scale food production systems. Quantitative natural genetic resistance to the R. solani has been identified in dicot crops, but has been more elusive in the small-grain monocots, including wheat and barley. Race-specific (gene-for-gene) resistance also has not been demonstrated in host-Rhizoctonia interactions. Our early research in engineered resistance showed that specific cell-wall degrading enzymes from Fusarium expressed in wheat partially suppress root loss caused by R. solani AG-8 and R. oryzae (teleomorph Waitea circinata var. circinata), causal agents of Rhizoctonia root rot in wheat and barley. We are currently exploring chromosome addition lines and synthetic wheat genotypes generated at CIMMYT as novel sources of resistance to Rhizoctonia species in the field. Additionally, plant innate immunity pathways have been implicated in resistance to necrotrophic pathogens by multiple independent laboratories. Plant innate immunity is a basal system of defense pathways and biochemical processes that provide partial protection against abiotic and biotic challenges. Innate immunity genes include those in oxidative stress metabolism, programmed cell death and jasmonic acid and ethylene signalling. Although these genes are expected to be difficult to induce or manipulate without non-target effects in the host, we are developing methods for testing candidate genes for their effects on suppression of root damage caused by R. solani AG-8 and R. oryzae. Significant progress and drawbacks in this and related areas will be summarized.