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Understanding soil suppressiveness towards the Sudden Death Syndrome / Soybean Cyst Nematode disease complex

Principal Investigator: Owen Wally and Lori Phillips

Research Institution: Agriculture and Agri-Food Canada

Timeline: April 2021 – July 2024  


  • Determine the biological component(s) that lead to soil being suppressive against SDS establishment and SCN proliferation.
  • Develop an understanding of timing required for initiation and establishment of suppressive soils.
  • Survey fields with SDS/SCN history and determine the level of inhibition within these fields.
  • Downstream potential for discovery of biocontrol agents and cultural practices for suppression of SDS and SCN.



  • Understanding of the impacts of the SDS/SCN suppressive soil microbiome can lead to environmentally and economically sustainable methods of maintaining high yielding soybeans in at-risk fields through beneficial agronomic practices.
  • Development of protocols for encouraging the establishment of suppressive soils.
  • Potential development of biocontrol agents will allow soybean producers to help control SDS and SCN in a prophylactic manner. There are currently very few options for control of these diseases in terms of biological or chemical treatment and those that are available have relatively limited potential in areas of high disease pressure. 


Scientific Summary:

Sudden Death Syndrome (SDS) and Soybean Cyst Nematodes (SCN) are among the most devastating diseases that infect soybeans in Southern Ontario. A field that had a history of severe SDS and SCN symptoms has been used as a disease nursery for screening disease tolerance for the past 15 years. However, disease symptoms have decreased recently despite favourable environmental conditions. Growth room bioassays indicated these soils have high endemic levels of SDS; however, no SDS symptoms develop even after inoculation. Interestingly, when the soil was sterilized prior to inoculation the plants exhibited extreme SDS symptoms, indicating a biotic influence underpinning disease suppression. In contrast, fields with more recent SDS infestations undergoing traditional rotations have little to no biotic suppression from the same assays. These same SDS suppressive fields also appear to mitigate the damage caused by SCN, indicating a robust suppression against the SDS/SCN disease complex.

Understanding the microbiological components within the soil that lead to this suppression and how this suppressiveness can be promoted in non-suppressive fields can lead to continual sustainable soybean production in Ontario. We are now able to apply advances in microbiological ‘omics methods and computational biology to identify the biological organisms, consortia, or interactions that facilitate this biotic suppression. Understanding these biotic contributions will lead to new methods to control highly destructive soybean diseases in a sustainable manner. Including the modification of existing rotational recommendations, use of organic amendments or potential direct applications of beneficial microbes.


External Funding Partners:

Agriculture & Agri-Food Canada