Submitted to: WSU Dryland Field Day Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/20/2014
Publication Date: 6/20/2014
Citation: Okubara, P.A., Schroeder, K.L., Paulitz, T.C. 2014. Distribution of Rhizoctonia Bare Patch and Root Rot in Eastern Washington and Relation to Climatic Variables. WSU Dryland Field Day Abstracts. 14-1. Pg.63.
Technical Abstract: Rhizoctonia is a fungus that attacks the roots of wheat and barley, causing a root rot and bare patch in the dryland wheat cropping area of the inland Pacific Northwest. Over the last 7 years, we have been investigating the distribution of this pathogen, using molecular methods based on extracting and quantifying DNA from soil. We want to answer the questions- where and how much fungus is present? From 2006 to 2008, we sampled 11 grower fields and 60 WA variety testing plots. What have we discovered about the distribution of this pathogen and disease? With Rhizoctonia solani AG-8, we tend to find higher populations in the lower precipitation areas, especially those having sandier soils. Figure 1 shows a map of these sampling sites. The square and star symbols show sites with higher levels of DNA in the soil, compared to the triangles and circles. The populations tend to be lower in the Palouse of eastern Washington, where we typically do not see bare patch, but find uneven stands and root rot. When we look at the correlations between populations of R. solani AG-8 and precipitation, we find a negative relationship- the higher populations (greater DNA quantities) are seen in lower precipitation areas, and lower populations in higher precipitation areas (Figure 2). The DNA values are on a log scale, so the sites in the low (200 mm) precipitation areas may have 10 to 100 times more DNA than sites in the 600 mm zones. This distribution agrees with the observation that bare patch is more widespread in the Ritzville/ Connell and Walla Walla-Dayton area than in the higher precipitation zones.