Description

Phytophthora root and stem rot (PRSR), caused by the soil-borne fungus Phytophthora sojae, is a common disease found throughout the United States.  PRSR has been ranked as a leading destructive soybean disease reportedly causing an annual loss of over 44 million bu from 1996-2009 (Koenning and Wrather, 2010; Wrather and Koenning, 2009).  A race is defined as a specific form of the pathogen that is characterized by the resistance genes it can defeat e.g., Race 1, Race 2, Race 3, etc. Currently there are over fifty identified races of P. sojae (Grau et al., 2004).

It is very important to select cultivars with resistance genes that are effective against the Phytophthora races present in the fields.  To select relevant crop lines with resistance genes, it is paramount that the Phytophthora race population status stay current.  By conducting periodic soil sampling, pathogen isolation and resistance gene characterization assays, researchers and producers can determine which resistance genes will provide the most effective control over the pathogen in that region.  To that end, it is important for the producers to be aware of the resistance genes that are present within their soybean varieties before purchasing.  Identification of resistance genes found within soybean varieties allows the producer to plant specific Phytophthora-resistant varieties tailored to their individual fields.  It also allows for an effective resistance gene-rotation system to minimize pathogen evolution.

NAGC has developed a test that allows for the identification of the Phytophthora sojae pathogen, allowing ND soybean producers to quickly identify the Phytophthora pathogen. An accurate course for remediation can then be determined. It can also be an indicator of what soybean producers might expect in a particular field the following year.

This project was funded in part by the North Dakota Soybean Council.

References

Grau, C. R., Dorrance, A. E., Bond, J. & Russin, J. S. 2004. Fungal Diseases. Soybeans: Improvement, Production, and Uses, 679-763-8.

Koenning, S. R. & Wrather, J. A. 2010. Suppression of Soybean Yield Potential in the Continental United States by Plant Diseases from 2006 to 2009. Plant Health Progress, 11, 5.

Wrather, A. & Koenning, S. 2009. Effects of Diseases on Soybean Yields in the United States 1996 to 2007. Plant Health Progress, 10, 24.