Soil nematode community structure and Rhizoctonia solani population dynamics across land-use intensities

Soil biological communities are increasingly studied in relation to soilborne pathogen populations and disease incidence in agricultural systems. This study examined how land-use intensity and soil biological structure influence Rhizoctonia solani DNA detected in field soils across Prince Edward Island, Canada. Field soils ( n = 59) representing high (2–3 years rotation), medium (4 years rotation), and low (undisturbed) land-use intensities were analyzed for R. solani DNA, soil chemical properties and nematode community composition. Across field soils, R. solani DNA concentrations were negatively associated with total C and N but positively related to particulate organic C and autoclaved citrate extractable protein, indicating relationships with both the quantity and quality of soil organic matter (SOM). A soybean microcosm experiment using a subset of 12 soils differing in land-use history and nematode community structure further assessed R. solani DNA and disease severity under controlled conditions. Soils with lower nematode structural indices and a history of disturbance exhibited higher R. solani DNA concentrations and greater disease severity, whereas undisturbed soils generally had lower values. Inoculation with R. solani AG2-2 LP resulted in reduced nematode structure indices. At the family level, Pratylenchidae and Aphelenchidae were positively correlated with disease severity, while Aporcelaimidae and Tylencholaimidae were negatively associated. Overall, R. solani DNA levels and disease severity were associated with SOM characteristics and food-web structure, highlighting links between soil properties, biological communities, and R. solani dynamics across land-use intensities.