Title: Real-time detection and quantification of Rhizoctonia and Pythium species on the Cook Agronomy Farm. Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 20, 2009
Publication Date: June 20, 2009
Citation: Schroeder, K.L., Paulitz, T.C., Okubara, P.A. 2009. Real-time detection and quantification of Rhizoctonia and Pythium species on the Cook Agronomy Farm. Meeting Abstract. 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. The process of identifying the pathogen present in a sample is laborious and the high diversity increases the difficulty in accurately identifying and quantifying the important species present in a field. Recently, real-time PCR assays were developed for both of these organisms to provide a new tool for more accurate measurements of pathogen populations. With this new tool, the biology and disease management strategies for these organisms can be better evaluated. Evidence from recent surveys for the presence of these pathogens suggests that various environmental and soil factors may influence the species composition and populations of these pathogens. This composition may also be influenced by crop rotation. To further evaluate the impact of crop rotation and spatial distribution of these pathogens, soil samples were collected from the Cook Agronomy Farm near Pullman, WA. This research farm was established in 1999 to test direct-seed cropping systems on a field scale and includes 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 BarocyclerTM and Mo-Bio Soil DNA kit, and PAGE 32 2009 FIELD DAY ABSTRACTS: HIGHLIGHTS OF RESEARCH PROGRESS 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. Pythium ultimum and P. irregulare group I, two of the more virulent species of Pythium, were seldom observed on this farm.