A comparison of baiting techniques to recover Pythium from soil and assessment of soybean seed treatment with a laboratory seed plate assay.

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Date

2024-05

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The Ohio State University

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Abstract

Pythium is a soil-borne oomycete pathogen that causes soybean seedling damping-off and seed rot soon after planting resulting in significant yield losses. Soil baiting techniques are amongst the most common methods to isolate oomycetes from soil samples. The objective of this experiment was to compare baiting techniques and selective media for the purpose of plant pathogen diagnostics. Soybean leaf discs, soybean seedlings, and rhododendron leaf discs were floated in 1:2 soil-water mixture to bait Pythium at 24- and 72-hour time points post incubation (i.e., baiting). Subsequently, the baits were plated on selective media (PARP and PBNIC) and incubated in the dark at 20–25°C for 72 hours. Colonies that emerged from the baits were counted and observed under the microscope for typical oomycete characteristics, such as lack of septation in the hyphae and presence of oospores and zoospores. Morphological and molecular characterization of these oomycete isolates is ongoing. The 72-hour time treatment resulted in 14% more oomycete colonies. Similarly, PARP selective medium resulted in 22% more oomycete colonies compared to PBNIC. It was also determined that soybean leaves baited oomycete species better than rhododendron leaves and soybean seedlings. Pythium isolates from this collection will be used to evaluate the effect of fungicide seed treatments on Pythium seedling blight and root rot of soybean.

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2nd Place at 2023 CFAES Poster Competition
Travel Award at the 2023 American Phytopathological Society North Central Division Meeting

Keywords

Oomycetes, Pythium, Soybean

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