Enhancing Sclerotinia stem rot research capacity and exploring new avenues of disease management through soybean canopy architecture traits
Sustainable Production
Crop protectionDiseaseField management
Lead Principal Investigator:
Megan McCaghey, University of Minnesota
Co-Principal Investigators:
Project Code:
Contributing Organization (Checkoff):
Institution Funded:
Brief Project Summary:
Minnesota researchers are working to reduce the severity of white mold in soybeans. By studying the aggressiveness levels of specific Sclerotinia sclerotiorum isolates, they can help breeders improve soybean resistance to white mold. They are also studying soybean plant shape, or plant architecture, and how quickly the soybeans reach canopy closure as a result, which factors into white mold development. Another aspect of this project includes developing apothecia for researchers to have reliable sclerotia to use inoculates for studies.
Key Beneficiaries:
#agronomists, #breeders, #farmers, #pathologists
Unique Keywords:
#canopy, #plant shape, #Sclerotinia sclerotiorum, #soybean diseases, #white mold
Information And Results
Project Summary

Sclerotinia stem rot (SSR), also known as white mold, is caused by the soilborne fungal pathogen Sclerotinia sclerotiorum and consistently ranks in the top ten diseases that reduce soybean yields in the United States (Bradley et al., 2021). Between the years of 2015 and 2019, yield losses from SSR amounted to 200,000,000 bushels of soybeans. In Minnesota, yield losses exceeded 37,000,000 bushels and approximately $334 million dollars were lost during these five years due to the disease (cropprotectionnetwork.com).

Managing SSR is complicated by a variety of factors. Crop rotation does not eradicate the pathogen since it can infect a wide range of crop plants. The hardened survival structures of the fungus, called sclerotia, can survive for many years in the soil and will initiate new infections when conditions are favorable. Chemical control can be effective, but there is a narrow range during which to apply fungicides (R1-R3 growth stages), and chemical control may not be economical if more tolerant varieties are planted (Dr. Damon Smith, badgercropdoc.com).

One of the most effective means to control any disease, including SSR, is the use of resistant cultivars. Scientific strides have been made in identifying genetic sources of SSR resistance through quantitative trait loci (QTL) mapping (Bastien et al. 2014; Vuong et al. 2008; Zhao et al. 2015). All resistance to SSR is partial (some degree of infection still occurs, even in tolerant cultivars), but disease severity can be significantly reduced when disease resistant cultivars are grown (McCaghey et al. 2017). Disease can also be reduced with wider row spacing and lower seeding rates, but these management strategies also result in lower yields (Webster et al. 2021).

Disease reduction with less canopy closure is likely due to a variety of factors including an altered micro-climate with less humidity and leaf moisture and a change in light quality and intensity. To cause disease in soybean, apothecia must first emerge. From the apothecia, infective ascospores are released. The formation of apothecia is very light dependent and requires exposure to wavelengths in the range of 276 and 319 nm (Thanning and Nilsson 2000). It is also likely that light dynamics in a closing canopy favor SSR development. The interaction of the soybean canopy with SSR development is an understudied area of research. If identified, plant architecture traits to reduce disease development may be useful for future resistance breeding efforts, especially when combined with physiological resistance.

To enhance disease resistance breeding in the in Minnesota, we propose foundational work to apply a panel of three Sclerotinia sclerotiorum isolates, collected throughout Minnesota, to comprehensively screen soybean line. We also propose developing and comparing field techniques for infesting research fields to conduct applied SSR research. Lastly, this project aims to define relationships between canopy architecture and S. sclerotiorum development, to provide another, underexplored consideration for disease resistance breeding to SSR.

Project Objectives

1. GOAL: Define relationship between canopy architecture and SSR development
Obj. 1) Characterize architectural traits and canopy closure of select lines in the field
Obj. 2) Define the genetic, SSR resistance of architecturally diverse lines
Obj. 3) Measure light penetration along with apothecia and SSR development

2. GOAL: Develop tools to improve the efficacy of resistance screening for SSR
Obj. 1) Develop a S. sclerotiorum isolate panel to screen for variety resistance
Obj. 2) Develop reliable S. sclerotiorum nurseries for future SSR field trials (continuing)

Project Deliverables

• Results will be presented at seminars and regional (Prairie Grains, Minnesota Ag Expo) and national meetings.
• Peer-reviewed research publications will be developed.
• A S. sclerotiorum screening panel will be developed for future SSR work.
• A research education and outreach opportunity will be available to students in my lab who are assisting with the project. The next generation of soybean researchers and will be trained in grower-driven research.
• New breeding opportunities will be explored through enhancing disease escape with plant architectural traits and candidate lines for breeding will be identified.
• Improved SSR resistance screening methods (through the characterization of S. sclerotiorum isolates and improved nursery methods), can lead to improved SSR research across University of Minnesota and the Sclerotinia community.
• Identification of lines with unique branching phenotypes can lead to candidates for quantitative trait loci (QTL) studies to identify genes related to branching phenotypes and disease resistance.
• Collaborations between researchers of various departments and universities will build bridges of expertise in soybean research to enhance each other’s work in soybean improvement.

Progress Of Work


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Updated February 29, 2024:

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Final Project Results

Benefit To Soybean Farmers

Disease management options for Sclerotinia stem rot are limited, and genetic resistance is one of the most effective lines of defense against any plant disease. This project will aim to improve resistance screening methods by developing a collection of S. sclerotiorum isolates that are typical of Minnesota, with a representative ability to cause disease symptoms in soybean. Additionally, uniform and reliable disease pressure developed in the field will allow me to share reliable data with growers due to consistent SSR disease pressure for variety and experimental trials. Finally, the development of SSR disease is very dependent on environmental conditions. Plant architecture may play an important role in creating conditions that are ideal for disease development. We will evaluate the importance of plant architectural traits for disease development. This work may lead to opportunities to further improve soybean resistance to SSR by breeding for architectural traits that discourage SSR development and improve yield. Ultimately, we aim to explore genetic/architectural management tools for growers to use in SSR-infested fields to avoid yield losses. Results will be provided to growers via outreach materials and at grower meetings.

A student will focus on the objectives described in this proposal for their master’s thesis. Through this project, students will learn more about research in soybeans and will develop as budding experts to assist with future production challenges through science.

Lastly, this project is collaborative and uses resources from researchers in different institutions and departments. These collaborative relationships will provide enhanced idea generation and pooled resources for future projects in Minnesota soybeans.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.