Rapid Quantification of Soilborne Pathogen Communities in Wheat-Based Long-Term Field Experiments

Area of Science:

• Agronomy
• Plant Pathology
• Soil Science

Background:

• Long-term agronomic trials (up to 84 years) in semiarid Oregon provide a unique dataset.
• Previous studies visually assessed disease, but inoculum density remained unquantified.
• Understanding pathogen dynamics is crucial for sustainable dryland farming.

Purpose of the Study:

• To quantify natural inoculum densities of 17 fungal and nematode pathogens.
• To assess the impact of crop type, tillage, rotation, soil fertility, and year on pathogen populations.
• To identify pathogen associations and previously unrecognized pathogens in these trials.

Main Methods:

• Soil DNA extraction and quantitative analysis of 17 target pathogens.
• Experiments included diverse crop rotations, tillage practices, and fertility regimes.
• Data collected over two years across eight distinct trials.

Main Results:

• Crop type, tillage, rotation, fertility, and year significantly influenced pathogen densities.
• Specific pathogen dominances varied between spring crops and continuous winter wheat.
• Some pathogens showed restricted host associations (e.g., Bipolaris sorokiniana, Phoma pinodella).
• Pathogen prevalence differed between cultivated and non-cultivated soils, and between annual cropping and wheat-fallow rotations.
• Significant treatment effects were more common in annually cropped experiments.
• Associations among pathogens were primarily observed in the oldest annual cereals experiment.
• Drechslera tritici-repentis and P. pinodella were identified for the first time at this location.

Conclusions:

• Agronomic practices profoundly shape root-infecting pathogen communities in rainfed systems.
• Long-term experiments are invaluable for understanding pathogen ecology and developing management strategies.
• This research identified key factors influencing pathogen dynamics and highlighted novel pathogen presences.