By Austin McCoy
Statewide soil sampling survey will help growers make decisions on what soybean cultivar to plant in fields with Phytophthora stem and root rot.
Phytophthora root and stem rot of soybean, caused by the oomycete Phytophthora sojae, is primarily controlled through planting resistant cultivars that contain race-specific Rps genes (Resistance to Phytophthora sojae) or partial resistance. These Rps genes provide race-specific resistance to multiple races of P. sojae.
However, as more Rps genes are deployed, we are seeing an increase in race, or pathotype, complexity in areas that regularly plant soybeans. This increase in complexity can lead to Rps genes becoming ineffective in a field where they have previously been used effectively. Partial resistance is also an effective means of managing Phytophthora, however this form of resistance is not expressed until plants have developed first true leaves.
Determining what pathotypes are found within Michigan will help soybean breeders identify what Rps genes should be incorporated into cultivars to control our P. sojae populations.
Michigan State University is currently conducting a statewide sampling survey to identify what pathotypes, or races, of Phytophthora sojae are currently found within Michigan. This study will allow farmers to make an informed decision on what soybean cultivars to plant in fields that have a history of Phytophthora stem and root rot.
Our goal is to produce an accurate depiction of the pathotype distribution within Michigan to help farmers and breeders determine what Rps genes will work best in the area. We would like support from farmers, crop inspectors and MSU Extension educators to help us sample as many counties in Michigan as possible.
If you would like to submit a soil sample, please include:
- One gallon of soil sampled from at least 10 different parts of a field known to have a history of Phytophthora root and stem rot.
- GPS coordinates of the field so we can map where each sample came from, or the nearest road intersection. (We recommend using Google maps to obtain GPS points in the field.)
- The date you collected the soil.
- Any information you can give us on field practices used, i.e., tillage practices, irrigation, previous crop planted, etc.