Database Research Summaries
2018 Determination of phytophthora sojae populations and assessment of management strategies

calendar_today Year of Research: 2018
update Posted On: 12/04/2019
group Martin Chilvers (Principal Investigator, Michigan State University)
bookmark Michigan Soybean Promotion Committee

Research Focus

The focus of this project is to survey pathotypes and examine management practices (seed treatments and resistance packages) that will enable up-to-date information be delivered to Michigan soybean farmers.


  • Collect soil and bait Phytophthora sojae and P. sansomeana isolates across Michigan.
  • Determine P. sojae pathotypes using soybean differentials (varieties with different Rps genes).
  • Determine in-vitro fungicide sensitivity of Phytophthora isolates to determine if fungicide chemistries are effective, and to monitor for shits in fungicide sensitivity.
  • Determine in-field management of P. sojae and P. sansomeana with varieties and seed treatments, including new seed treatments and varieties.
  • Train an MSc graduate student.


  1. Determining effective resistance genes to P. sojae allows for informed management recommendations to farmers as well as informing soybean breeders on a shift in the populations pathotype for coordinated breeding of new lines. 1K and 1C genes are the most readily available for Phytophthora resistance and also two of the most susceptible identified in our study. Likewise, two genes, 3B and 4, were identified as potentially useful, but are not currently available in any commercial soybean lines.
  2. Phytophthora sansomeana appears to have a wide host range, showing an ability to cause disease on a variety of commonly planted field crops in Michigan. This could become problematic if the pathogen spreads as all hosts tested appear to be able to act as hosts and soybean appears to be the most susceptible and important host.
  3. Fortunately, P. sansomeana was only identified in two fields in Michigan in this survey, but is likely present in more fields that were not sampled.
  4. Field trial data suggests that in high oomycete pressured fields a seed treatment containing a fungicide active against oomycetes would significantly increase stand. However, yield data suggests that there is little significant increase in yield when using a seed treatment.
  5. Economic benefits of seed treatments have not yet been evaluated for this study.


  • This will improve Phytopthora root and stem rot management through variety selection and seed treatments.

For more information about this research project, please visit the National Soybean Checkoff Research Database.

Funded in part by the soybean checkoff.