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ARS Home » Northeast Area » Frederick, Maryland » Foreign Disease-Weed Science Research » Research » Publications at this Location » Publication #412212
Research Project: Diagnostics and Biological Approaches for Management of Emerging Oomycete Plant Pathogens

Location: Foreign Disease-Weed Science Research

Title: First global report of Hyaloperonospora brassicae in commercial broccoli and cabbage microgreens

Author
item Pfeufer, Emily
item SURESH, LOHINI,P - Oak Ridge Institute For Science And Education (ORISE)
item GROBEN, GLEN - Oak Ridge Institute For Science And Education (ORISE)

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2024
Publication Date: 5/22/2024
Citation: Pfeufer, E., Suresh, L., Groben, G. 2024. First global report of Hyaloperonospora brassicae in commercial broccoli and cabbage microgreens. Plant Disease. 108:7. https://doi.org/10.1094/PDIS-01-24-0266-PDN.
DOI: https://doi.org/10.1094/PDIS-01-24-0266-PDN

Interpretive Summary: Brassica microgreens are a nutrition-enhancing component of modern culinary dishes, that are expanding in commercial production. Kale, broccoli, and cabbage microgreens were observed with chlorotic and necrotic symptoms on cotyledons, accompanied by sporulation consistent with downy mildew disease. Based on morphology and host identity, a Hyaloperonospora species was suggested. Experiments were conducted to confirm transmissibility to lab-grown plants as well as genetically confirm the species causing the symptoms. Two experiments confirmed that the causal agent was transmissible to lab-grown kale, broccoli, cabbage, and cauliflower seedlings, causing symptoms similar to those observed on the originally affected plants. Sporulation of the pathogen was apparent on lab-grown plants one week after inoculation. Genetic analysis of the cox1 mitochondrial gene, a frequently-used region for speciating oomycete plant pathogens, indicated 99.5% similarity to the reference genome of Hyaloperonospora brassicae. This is the first report of H. brassicae causing downy mildew on commercial brassica microgreens, which are a nutrition-enhancing addition to modern culinary dishes.

Technical Abstract: Brassica microgreens are used to enhance the color, texture, and nutritional value of many modern culinary dishes. A destructive disease was found affecting kale, broccoli, and cabbage microgreen crops from Michigan, at a high rate. Seed leaves were yellow, gray, and dying, and the disease agent was found on undersides of leaves in very humid conditions. Based on its appearance, a downy mildew was suspected as the disease agent. Two tests showed that the disease could be transferred from the original material to lab-grown plants. Genetic analysis of the disease agent confirmed the identification as a downy mildew caused by the water mold Hyaloperonospora brassicae. These findings are important to microgreen growers, who may experience yield and economic losses, as well as consumers who utilize microgreens in their dishes.