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Ontario Grain Farmer Magazine

Survey and management of soybean diseases

Principal Investigator: Owen Wally

Research Institution: Agriculture and Agri-Food Canada (AAFC)

Timeline: June 2016 – March 2019

Objectives:

  • Conduct an up-to-date disease survey in Ontario soybean fields for pathogen distribution and levels.
  • Optimize existing molecular biology methods for quantification of soil pathogen load.
  • Determine thresholds for root diseases for soybeans and field risk for disease outbreak (2017-2018).

 Impacts:

  • The reduction in the cost and time involved in determining the presence and quantity of pathogens in field soil over time using molecular methods will enable growers, industry stakeholders and fellow researchers to identify and determine incidence levels and damage thresholds within soybean fields and allow better management of pests.
  • The improved understanding of key risk factors for soybean pathogen development will allow growers to use integrated pest management strategies including:
    • Planting resistant soybean varieties.
    • Using appropriate crop rotations.
    • Accurate choice of chemical control and timing of application.

Scientific Summary:

Losses due to disease continue to be among the major limitations on soybean yield in Ontario. Surveys of fields were conducted during the 2016, 2017 and 2018 growing seasons, with most of the sampling focused on soil due to higher stability than plant samples. A total of 337 fields were sampled from Essex county to the Ottawa Valley. From these fields over 500 unique organisms were recovered and identified by morphology and DNA barcoding. These included 186 isolates of Phytophthora sojae, of which 90 were “pathotyped” (race determination); the remainder are in the process of being “pathotyped” to determine if there are effective resistance genes available. Over 170 unique isolates of Pythium were recovered representing over 30 different species. Though their virulence was not assessed, these included three Pythium species that have not previously been reported as pathogenic on soybean. Fusarium virguliforme was isolated from 28 fields, with the isolates transferred to the Canadian Culture collection.

Molecular protocols were optimized for F. virguliforme and soybean cyst nematode (SCN) in Ontario fields, with detection thresholds lower than previously reported using updated technologies.

Disease thresholds were partially determined for F. virguliforme; however, the disease is not linear with dose, and field conditions, rotations and microbiome play a major role in disease establishment. The thresholds that we discovered were generally lower than reported previously in the literature, especially in soil with coarser textures.

This project was an initial investigation by researchers at the AAFC Harrow Research and Development Center along with OMAFRA to build initial capacity and a framework for understanding the prevalence and quantity of soybean diseases. This information will be used to identify patterns of risk factors associated with development of disease outbreaks, and to eventually develop methods to mitigate risk factors associated with disease.

External Funding Partners:

None

Project Related Publications:

King, C. 2018. Scoping out soybean disease in Ontario. Top Crop Manager. March Issue.

Moyer, J. 2017. A regional approach: Research to understand Ontario soybean diseases. Ontario Grain Farmer. 8(5).