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ARS Home » Northeast Area » Frederick, Maryland » Foreign Disease-Weed Science Research » Research » Publications at this Location » Publication #403081

Research Project: Diagnostics and Biological Approaches for Management of Emerging Oomycete Plant Pathogens

Location: Foreign Disease-Weed Science Research

Title: Germination of a spinach seedling infected with Peronospora effusa from seeds infested with oospores

item Shishkoff, Nina
item MCGRATH, MARGARET TUTTLE - Cornell University

Submitted to: American Phytopathological Society Potomac Division Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/22/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Several occurrences of downy mildew in commercial plantings of spinach in winter tunnels in the Northeast since 2014 were the impetus for research undertaken to determine if contaminated seed could be the source of such outbreaks. In January 2023, seed was obtained of two varieties that had been associated with outbreaks. Seeds were examined microscopically to determine what percent were infested with downy mildew oospores. A slice of the outer seed coat was taken from each infested seed to determine oospore viability by plasmolysis in a 4 M NaCl solution and then, the seeds were placed on moist filter paper in plastic Petri dishes that were kept in a greenhouse at 18 C until they germinated. Infestation rates were 0-3%, but in one variety, an abundance of oospores were observed on each infested seed. Many of the oospores appeared viable. One of 62 seedlings germinating from infested seed became systemically infected. DNA sequencing confirmed the presence of Peronospora effusa. These results yield additional confirmation that the spinach downy mildew pathogen is seed-borne.