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ARS Home » Northeast Area » Frederick, Maryland » Foreign Disease-Weed Science Research » Research » Publications at this Location » Publication #425665
Research Project: Integrative Genomic and Biological Approaches to Detect and Manage Emerging Foreign Fungal and Oomycete Plant Pathogens

Location: Foreign Disease-Weed Science Research

Title: Behavior of rose downy mildew on leaves and flowers of a variety of plants in the Rosaceae

Author
item Shishkoff, Nina

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/13/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: N/a

Technical Abstract: The downy mildews on roses and brambles are sometimes considered the same species, Peronospora sparsa, and sometimes considered to be two species, P. sparsa on roses, and P. rubi on brambles. P. sparsa has also been reported from cherry laurel (Prunus laurocerasus). We have have performed host range tests on detached leaves and petals of Rosa multiflora, wild raspberry (Rubus strigosus), cherry laurel, spirea (Spiraea cantoniensis), quince (Cydonia oblonga), and shadblow (Amelanchier canadensis), among others, comparing susceptibility with leaves and petals of miniature roses inoculated with RDM at the same time. Sporangia collected from miniature rose petals were used as inoculum (a water suspension of approx. 15,000 spores/mL), then a micropipette was used to put one or two 20 uL drops of suspension on each leaf or petal, incubating in moist chambers consisting of Petri dishes lined with moist Whatman Filter paper. After 8-10 days, the number of infected leaves or petals were counted. Miniature roses were most susceptible, and for other hosts, infection was generally greater on flower petals or exclusively on petals compared to leaves. Haustoria and oogonia were often observed in infected petals cleared in ethanol. Results suggest that while P. sparsa can weakly infect various weakly infect the leaves of plants in the Rosaceae, there was less host specificity observed in flower infections. It has not escaped our notice that our results immediately suggest a possible mechanism for adaptation to new hosts.