Project Details:

Determination of Phytophthora sojae populations and assessment of management strategies

Parent Project: Determination of Phytophthora sojae populations and assessment of management strategies
Checkoff Organization:Michigan Soybean Promotion Committee
Categories:Soybean diseases, Breeding & genetics, Climate change
Organization Project Code:2013
Project Year:2020
Lead Principal Investigator:Martin Chilvers (Michigan State University)
Co-Principal Investigators:

Contributing Organizations

Funding Institutions

Information and Results

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Project Summary

Phytophthora sojae and P. sansomeana have the potential to rob yield from Michigan soybean producers. It has been 20 years (1993-1997) since a detailed survey has been conducted for the Phytophthora sojae pathotypes (races) present in Michigan. We often receive questions from growers and seed dealers regarding which Rps resistance genes, trait packages and seed treatments should be used for Phytophthora stem and root rot management. This survey of pathotypes and examination of management practices (seed treatments and resistance packages) will enable us to provide up-to-date information to Michigan soybean farmers.

Phytophthora sansomeana is a newly described species that can cause disease on soybean, corn and other plant species. Not much is known about P. sansomeana and the damage that it may be causing. It is also not known how widespread P. sansomeana is in Michigan. Unlike Phytophthora sojae, there are currently no known resistance genes to P. sansomeana, therefore current management relies on the use of effective seed treatments to mitigate stand and yield losses. Understanding the effect of seed treatments on soil borne pathogens like Phytophthora is critical for continued effective control.

Project Objectives

1. Collect soil and bait Phytophthora sojae and P. sansomeana isolates from across Michigan [COMPLETED]
2. Determine P. sojae pathotypes using soybean differentials (varieties with different Rps genes) [COMPLETED]
3. Determine host range and aggressiveness of Phytophthora sansomeana [COMPLETED]
4. Determine in-vitro fungicide sensitivity of Phytophthora isolates to determine if fungicide chemistries are effective, and to monitor for shifts in fungicide sensitivity.
5. Determine in-field management of P. sojae and P. sansomeana with varieties and seed treatments, including new seed treatments and varieties. [P. sojae trial COMPLETED; P. sansomeana trials starting 2020]
6. Train a PhD graduate student

Project Deliverables

Performance of the graduate student and project progress will be evaluated monthly through lab meetings. Resources developed such as isolate collections will be made available to soybean breeders for the screening of germplasm resistance.

Progress of Work

Updated September 23, 2020:
Management of Phytophthora sansomeana with variety resistance x seed treatment trial
Objective: field trial to determine yield loss due to P. sansomeana and the benefit of variety resistance and seed treatment and their interaction for the management of P. sansomeana.
The trial is demonstrating the importance of seed treatment and variety selection for the management of P. sansomeana and yield data will be available at the end of the 2020 season.

Management of Phytophthora sansomeana with plant resistance
Objective: field trial to confirm a novel source of soybean resistance to P. sansomeana.
The trial is being conducted in conjunction with Feng Wang from Dechun Wang’s lab, and has demonstrated that a novel resistance gene has been identified for P. sansomeana management. To aid in confirming the type of resistance we are also sequencing the genome of P. sansomeana

Determination of Rps genes for the management of Phytophthora sojae
Objective: Identify Rps genes that confer resistance to P. sojae pathotypes in Michigan.
Phytophthora sojae isolates can be classified into pathotypes based on their ability to overcome soybean (Rps) resistance genes. These Rps genes confer absolute resistance to P. sojae at all plant growth stages, however these resistance genes can be overcome by P. sojae, hence it is important to regularly check on how these genes are performing. In contrast field tolerance or partial resistance does not confer complete resistance to P. sojae, but is less likely to “break down”. Table 1 demonstrates that 1c and 1k are ineffective against many isolates of P. sojae in Michigan, however 3a, 3c and 4 control most isolates.
Partial resistance is another option for management or it can be paired with Rps genes, however partial resistance takes time to initiate in the plant, and should be paired with a seed treatment to provide initial protection of the young plant as the partial resistance develops.

Fungicide sensitivity data for P. sojae and P. sansomeana
Objective: screen fungicides available for Phytophthora management
New fungicides including ethaboxam, oxathiapiprolin have become available recently for the management of Phytophthora and or Pythium species. It is important to understand the efficacy of these fungicides and to determine a baseline sensitivity for fungicide resistance monitoring. In this study we have examined these new fungicides, as well as older chemistries including mefenoxam (metalaxyl) and pyraclostrobin.

Pythium real-time qPCR assay and database
Objective: develop a molecular database so to enable the development of rapid disease identification tools
In this project molecular sequences are being compiled for the many Pythium species that we encounter in soybean and field crops. This database will facilitate the development or rapid diagnostic tools to help farmers in identifying the cause of seedling disease and root rot.

Final Project Results

Benefit to Soybean Farmers

Research results will be distributed through field days and extension meetings. A multi-state extension bulletin will be produced and made available through the Crop Protection Network ( and articles will be created for Michigan Soybean News and MSUE News for Ag. YouTube videos will also be created to report results, and social media, such as Twitter and Facebook, will be used to relay take home messages to the Michigan agricultural community.

Performance Metrics

Project Years