Sclerotinia sclerotiorum is a hemibiotrophic, filamentous, ascomycete that poses a formidable threat to a broad range of agronomically important crops, including soybean. During infection in the infected field, S. sclerotiorum mycelia has a cottony (moldy growth) appearance, also called white mold (Fig 1). White mold is a recurring and significant problem for Minnesota soybean growers. Cultural management of white mold, such as crop rotation and row spacing modification, has limited economic success. In the Minnesota soybean breeding program, several varieties of soybeans have been bred. Cultural management of white mold, such as crop rotation and row spacing modification, has limited success; hence, white mold management largely depends on fungicide treatment. S. sclerotiorum forms a black survival structure called sclerotia at the end of the disease cycle. These sclerotia can survive up to 7 years in the soil, contributing to a long-term presence in the field and making it difficult to manage with traditional management strategies. Planting a susceptible variety of soybean can increase the soil's sclerotia load, making it economically unviable to grow the same variety in the following years. One of the most sustainable

and economical ways to control crop diseases is to identify and generate resistant varieties of plants. Unfortunately, no soybean lines are known to have complete resistance against white mold.

Objective 1. Continuing white mold disease screening on the soybean varieties produced through the UMN soybean breeding program and commercial varieties in the naturally infested field and controlled environment, greenhouse/growth chamber.

Goal 1. The study aims to identify white mold resistant lines/cultivars for growers and use the best lines as parental lines for future breeding programs for sustained breeding efforts towards white mold-resistant cultivars production. The study results will be published through the MN Ag Experiment Station publications.

Goal 2. Provide an unbiased source of information to growers on the level of white mold resistance in commercially available varieties and their performance at S. sclerotiorum infested sites.

Objective 2. Continue to evaluate the yield impact of white mold in treated and non-treated soybean varieties and quantify their yield potential under standard farm management practices.

Goals 1. Provide a yield potential of soybean lines under S. sclerotiorum disease pressure.

Results from the proposed research will be presented at Minnesota Soybean Research and Promotion Council events such as Ag-Expo, the MN Soybean tent at Farmfest, and/or the MN Soybean Booth at Big Iron. Short videos (< 2 minutes each), for use on social media, introducing students (graduate and undergraduate), post-docs and other staff associated with the project are also requested. We are about to complete our first year of study but would like to continue for
next two year to have a comprehensive result. The study will lead to the identification of new genetic resources for breeding new soybean varieties for better yield and white mold resistance. The research will also be published in extension or Minnesota Soybean Minneline articles.

Update:

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The proposed research addresses three areas targeted by the Production Action Team's mission statement: (1) Pest management; (2) Plant breeding and functional genomics; (3) White mold (Sclerotinia stem rot). The benefit of this research is three-pronged and will positively impact MN soybean farmers. These are –

1. The study will identify resistant lines out of 48 soybean lines, including some commercial varieties. This will help Soybean growers to make an informed decision about planting white mold resistant varieties.

2. The identified white mold resistant and higher yield cultivars can become important genetic resources for future breeding program decisions and local growers' use.