Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: May 15, 2009
Publication Date: June 2, 2009
Citation: Schroeder, K.L., Paulitz, T.C., Okubara, P.A. 2009. Incidence and spatial distribution of Rhizoctonia and Pythium species determined with real-time PCR. Phytopathology 99: S115. Technical Abstract: Populations of Rhizoctonia and Pythium are diverse in eastern Washington, with multiple species/anastomosis groups present throughout the region and within individual fields. Recent evidence suggests that species composition may be influenced by crop rotation. The Cook Agronomy Farm near Pullman, WA was established in 1999 to test direct-seed cropping systems on a field scale, with 369 GPS sampling locations spaced every 30 m. A three-year rotation was established to include winter wheat-alternate crop-spring wheat, with each rotation occurring every year. The alternate crops consisted of a winter and/or spring variety of pea, lentil, barley or canola. Soil samples were collected from about 115 sites from the spring wheat portion of the field following the alternate crop. DNA was extracted from each soil sample using a Barocycler™ and Mo-Bio Soil DNA kit, and quantified with species specific primers and real-time PCR. Rhizoctonia solani AG-2-1 occurred more frequently in fields with a history of canola, with a higher frequency following spring canola (48% of sites) compared to winter canola (28%). Rhizoctonia oryzae was detected more often following winter alternate crops (39–44%) than spring crops (24–37%). Of four Pythium species examined, P. irregulare group IV and P. rostratifingens had the highest incidence of occurrence (66% and 67% respectively). These species of Pythium were also higher following winter canola and pea versus spring canola and pea.