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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Sunflower Improvement Research » Research » Publications at this Location » Publication #408006
Research Project: Improvement of Sclerotinia Disease Resistance and Management

Location: Sunflower Improvement Research

Title: Fungicide sensitivity of sclerotinia sclerotiorum from U.S. soybean and dry bean, compared to different regions and climates

Author
item NIETO-LOPEZ, EDGAR - University Of Nebraska
item JUSTO MIORINI, THOMAS - University Of Nebraska
item WULKOP-GIL, CRISTIAN - University Of Nebraska
item CHILVERS, MARTIN - Michigan State University
item GIESLER, LOREN - University Of Nebraska
item JACKSON-ZIEMS, TAMRA - University Of Nebraska
item KABBAGE, MEHDI - University Of Wisconsin
item MUELLER, DAREN - Iowa State University
item SMITH, DAMON - University Of Wisconsin
item TOVAR-PEDRAZA, JUAN - Center For Research In Food And Development (CIAD)
item WILLBUR, JAIME - University Of Wisconsin
item EVERHART, SYDNEY - University Of Nebraska

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2023
Publication Date: 8/18/2023
Citation: Nieto-Lopez, E.H., Justo Miorini, T.J., Wulkop-Gil, C.A., Chilvers, M.I., Giesler, L.J., Jackson-Ziems, T.A., Kabbage, M., Mueller, D.S., Smith, D.L., Tovar-Pedraza, J.M., Willbur, J.F., Everhart, S.E. 2023. Fungicide sensitivity of sclerotinia sclerotiorum from U.S. soybean and dry bean, compared to different regions and climates. Plant Disease. 107(8):2395-2406. https://doi.org/10.1094/PDIS-07-22-1707-RE.
DOI: https://doi.org/10.1094/PDIS-07-22-1707-RE

Interpretive Summary: Continued use of fungicides is needed on dry bean and soybean to deal with fungal diseases; however, there is increasing concern that this may lead to fungicide resistance or reduced sensitivity to the most commonly used fungicides. Therefore, the goals of this research were to provide a current look at fungicide sensitivity and comparison of the U.S. fungal isolates of the white mold pathogen. Fungal samples were collected from dry bean versus soybean fields; fields with different levels of fungicide application; and isolates that had received fungicide applications of a single active ingredient from the United States versus tropical and subtropical regions in Brazil and Mexico. We also looked at genetic mutations occurring within these isolates that might confer reduced sensitivity or resistance to specific fungicides. This study established specific fungicide concentrations that can be used for further resistance monitoring and baseline sensitivity of the white mold pathogen to two common fungicides. This information will be used to improve short- and long-term fungicide management recommendations for white mold diseases on soybean and dry bean to reduce the risk of fungicide failures in commercial fields.

Technical Abstract: Fungicide use is integral to reduce yield loss from Sclerotinia sclerotiorum on dry bean and soybean. Increasing fungicide use against this fungus may lead to resistance to the most common fungicides. Resistance has been reported in Brazil (Glycine max) and China (Brassica napus subsp. napus), however, few studies have investigated fungicide sensitivity of S. sclerotiorum in the United States. This work was conducted to determine if there was a difference in fungicide sensitivity of S. sclerotiorum isolates in the United States from: (i) dry bean versus soybean and (ii) fields with different frequencies of fungicide application. We further hypothesized that isolates with fungicide applications of a single active ingredient from tropical Brazil and subtropical Mexico were less sensitive than temperate U.S. isolates due to different management practices and climates. The EC50(D) fungicide sensitivity of 512 S. sclerotiorum isolates from the United States (443), Brazil (36), and Mexico (33) was determined using a discriminatory concentration (DC) previously identified for tetraconazole (2.0 ppm; EC50(D) range of 0.197 to 2.27 ppm), boscalid (0.2; 0.042 to 0.222), picoxystrobin (0.01; 0.006 to 0.027), and thiophanate-methyl, which had a qualitative DC of 10 ppm. Among the 10 least sensitive isolates to boscalid and picoxystrobin, 2 presented mutations known to confer resistance in the SdhB (qualitative) and SdhC (quantitative) genes; however, no strong resistance was found. This study established novel DCs that can be used for further resistance monitoring and baseline sensitivity of S. sclerotiorum to tetraconazole worldwide plus baseline sensitivity to boscalid in the United States.