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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #401786

Research Project: Disease Management and Improved Detection Systems for Control of Pathogens of Vegetables and Strawberries

Location: Crop Improvement and Protection Research

Title: Seed transmission of spinach downy mildew

item Clark, Kelley
item Kandel, Shyam
item Mou, Beiquan
item CORRELL, JAMES - University Of Arkansas
item Klosterman, Steven

Submitted to: International Congress of Plant Pathology Abstracts and Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 8/24/2023
Publication Date: 8/24/2023
Citation: Clark, K.J., Kandel, S.L., Mou, B., Correll, J.C., Klosterman, S.J. 2023. Seed transmission of spinach downy mildew. International Congress of Plant Pathology, August 20-25, 2023, Lyon, France.

Interpretive Summary:

Technical Abstract: Spinach downy mildew, caused by the oomycete pathogen Peronospora effusa, remains a constraint on spinach production. New races of P. effusa continue to appear and can overcome cultivar resistance. Spread of the pathogen via airborne sporangia is well established. However, the role of oospores from seed and infected crop debris has been long debated and remained uncertain. We have found oospores to be present in around 19% of evaluated spinach seed lots. To evaluate seedborne downy mildew transmission, we used isolated glass chambers to grow out oospore-infested spinach seeds, and seeds mixed with oospore-infested crop debris in two independent trials. Downy mildew diseased spinach plants were found 37 days after planting in the first trial, and 34 days after planting in the second trial, in glass chambers that contained one of two oospore-infested seed lots or seeds coated with oospore-infested leaves. Spinach plants in glass chambers initiated from seeds without oospores did not show downy mildew symptoms. These findings provide evidence of seed transmission of downy mildew to spinach plants via oospores and suggest management practices such as seed treatments to reduce the primary inoculum of the pathogen are needed.