Analysis of Downy Mildew Seed Transmission in Spinach

Authors: Clark, Kelley; Kandel, Shyam; CORRELL, JAMES - University Of Arkansas; Klosterman, Steven

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2022
Publication Date: N/A
Citation: N/A

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 disease resistance. Spread of the pathogen via airborne sporangia is well established, however, the roles of other potential inoculum sources, including oospores from seed and infected crop debris, has remained uncertain. From previous efforts, we’ve found oospores to be present in around 17% of evaluated spinach seed lots, yet direct ties to their involvement the disease cycle have been lacking and the obligate nature of the pathogen has made examining this challenging. We used controlled isolator chambers to grow out oospore-infested spinach seeds, and seeds mixed with oospore-infested crop debris to evaluate seedborne downy mildew transmission. Downy mildew diseased spinach plants were found 37 days after planting in isolator chambers that contained one of the two oospore-infested seed lots, and the seeds coated in oospore-infested leaves. Spinach plants in isolator chambers initiated from seeds without oospores did not show downy mildew symptoms. These findings present evidence of oospore-borne seed transmission of downy mildew to spinach plants though the experiment requires replication with the same seed samples and oospores.