Cucurbit Downy Mildew

Downy mildew is an important disease of cucurbits (e.g., cucumbers, melons, etc.) caused by the obligate pathogen Pseudoperonospora cubensis.  Historically, cucumber (Cucumis sativus) in the United States has been resistant to downy mildew, but introduction of a potential new pathotype of P. cubensishas been causing devastating losses in recent years.  Understanding the molecular genetic mechanisms between host and pathogen during the infection process will enable us to elucidate the mechanisms behind infection and disease progression and allow us to identify potential strategies for breeding downy midlew resistant cultivars.Current projects in the Day lab focus on building genomic resources of Ps. cubensis, including sequencing and annotation of the genome, developing tools to characterize the Ps. cubensis-cucumber interaction, and understanding mechanisms of Ps. cubensis virulence through the study of effector proteins. In addition, with the lab of Mary Hausbeck, we are working to develop collaborations that will bring the research developed in our labs to the field, and to growers.
pcub-figure-1The cucumber-Pseudoperonospora cubensis interaction.
A) Downy mildew disease phenotype on cucumber ‘Vlaspik.’ B) Close-up of typical yellow angular lesions. C) Underside of infected cucumber leaf, note sporangia. D) Purified sporangia of Ps. cubensis. E) DIC image of infected cucumber leaf. H, haustorium; IH, intercellular hyphae; S, stomata. F) Brightfield image of aniline blue stained leaf section described in “E.”

Recent publications related to this work can be found:

Savory EA, Adhikari BN, Hamilton JP, Vaillancourt B, Buell CR, et al. (2012) mRNA-Seq Analysis of the Pseudoperonospora cubensis Transcriptome During Cucumber (Cucumis sativus L.) Infection. PLoS ONE 7(4): e35796. doi:10.1371/journal.pone.0035796

Adhikari BN, Savory EA, Vaillancourt B, Childs KL, Hamilton JP, et al. (2012) Expression Profiling of Cucumis sativus in Response to Infection by Pseudoperonospora cubensis. PLoS ONE 7(4): e34954. doi:10.1371/journal.pone.0034954

Savory, E.A., Zou , C, Adhikari, B.N., Hamilton, J.P., Buell, C.R., Shiu, S.-H., and Day, B. (2012) Alternative Splicing of a Multi-Drug Transporter from Pseudoperonospora cubensis Generates an RXLR Effector Protein That Elicits a Rapid Cell Death.  PLoS ONE 7(4): e34701. doi:10.1371/journal.pone.0034701.

Runge F., Telle S., Ploch S., Savory, E., Day B., Sharma R., and Thines, Marco. 2011. The inclusion of downy mildews in a multi-locus-dataset and its reanalysis reveals a high degree of paraphyly in Phytophthora. IMA Fungus 2: 163-171.

Additional Downy Mildew Resources:

Downy Mildew Information for Growers (Hausbeck lab, MSU)

Managing Downy Mildew in Cucurbits (Vegetable MD Online, Cornell University)

Cucurbit Downy Mildew Forecasting (North American Plant Disease Forecast Center)