Skip to main content
ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Disease and Pest Management Research Unit » Research » Publications at this Location » Publication #419034
Research Project: Knowledge Based Tools for Exotic and Emerging Diseases of Small Fruit and Nursery Crops

Location: Horticultural Crops Disease and Pest Management Research Unit

Title: Molecular characterization of Botrytis isolates from blueberries and red raspberries in the Pacific Northwest with resistance to SDHI fungicides

Author
item BARAL, ROSHANI - Washington State University
item Delong, Jeffery
item McGhee, Gayle
item Stockwell, Virginia
item MATTUPALLI, CHAKRADHAR - Washington State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2025
Publication Date: 5/16/2025
Citation: Baral, R., Delong, J.A., Mcghee, G., Stockwell, V.O., Mattupalli, C. 2025. Molecular characterization of Botrytis isolates from blueberries and red raspberries in the Pacific Northwest with resistance to SDHI fungicides. Plant Disease. https://doi.org/10.1094/PDIS-12-24-2576-SC.
DOI: https://doi.org/10.1094/PDIS-12-24-2576-SC

Interpretive Summary: Washington and Oregon lead the nation in production of blueberries and raspberries with a total crop value of $482 million. This production is threatened by occurrence 'gray mold' caused by the fungus Botrytis. This threat results in growers making numerous fungicide applications from bloom to berry harvest, thus increasing the potential for resistance to fungicides such as succinate dehydrogenase inhibitor (SDHI). We found Botrytis isolates resistant to several of the SDHI fungicides currently used for disease management. We also detected genetic mutations in these isolates that confer SDHI resistance. This information will aid growers in making informed decisions on fungicide selection and rotation for resistance management and effective gray mold management.

Technical Abstract: Botrytis cinerea, a high-risk pathogen for fungicide resistance development, poses a significant threat to yield and fruit quality of blueberries and red raspberries in the Pacific Northwest. Succinate dehydrogenase inhibitor (SDHI) fungicides are effective botryticides but are considered medium to high resistance risk for Botrytis. Analysis of sdhB sequences from Botrytis isolates (n = 279) exhibiting in vitro resistance to any of four SDHIs (boscalid, fluxapyroxad, fluopyram, and isofetamid) revealed six previously characterized mutations: N230I, P225F, H272R, H272V, H272Y, and I274V, at frequencies of 40, 23, 22, 9, 5, and 1%, respectively. Different mutations in the sdhB gene resulted in twelve phenotypic profiles exhibiting resistance among the four SDHIs. In contrast, sdhC and sdhD sequences revealed no consistent mutations linked to a particular fungicide resistance phenotypic profile. High frequencies (72%) of P225F, H272V, and N230I mutations in sdhB, which confer cross-resistance to multiple SDHI fungicides, emphasizes the need for balanced use and rotation of fungicides to effectively manage Botrytis in blueberry and red raspberry fields in the Pacific Northwest.