Effect of Crop Rotation on the Soil Pathogen Population Dynamics and Canola Seedling Establishment

Impact of long-term crop rotations on populations of soilborne pathogens in the genera Fusarium, Pythium and Rhizoctonia and on canola seedling establishment and development was evaluated under controlled conditions. Soil samples were collected from two crop rotation experiments conducted at two sites in Saskatchewan, Canada. A part of the 2006-soil sample of each rotation was sterilized to compare canola seedling growth with and without soilborne pathogens. With 2007-soil, the sterilization treatment was replaced with a fungicide seed treatment (Apron Maxx) to assess the potential to reduce seedling diseases. Populations of Fusarium, Pythium and Rhizoctonia sp. were estimated in the soil of each rotation using dilution plating onto selective media for each fungus. Higher seedling emergence and increased growth of canola were obtained in the sterilized soil or due to seed treatment. Fusarium was the predominant genus followed by Pythium and Rhizoctonia sp. in the soil of both sites. This study suggests that diverse crop in the rotation may reduce the populations of Fusarium, Pythium and Rhizoctonia in the soil and may contribute to improve the overall growth of canola.