Cucurbit Downy Mildew (Pseudoperonospora cubensis): Cucumber Resistance

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dc.contributor.authorCooper, Jessica G.en
dc.contributor.committeechairRideout, Steven L.en
dc.contributor.committeememberDonofrio, Nicole M.en
dc.contributor.committeememberBaudoin, Antonius B.en
dc.contributor.departmentPlant Pathology, Physiology, and Weed Scienceen
dc.date.accessioned2014-07-18T17:32:32Zen
dc.date.available2014-07-18T17:32:32Zen
dc.date.issued2013-01-23en
dc.description.abstractPseudoperonospora cubensis (Bert. et Curt) Rost. is the causal agent of cucurbit downy mildew (CDM). It is the most damaging cucumber pathogen on the Eastern Shore of Virginia and eastern parts of the United States. Pseudoperonospora cubensis is an obligate oomycete pathogen, infecting crops within the Cucurbitaceae family. The disease is characterized by angular chlorotic lesions and a downy or felt-like appearance on the abaxial side of the leaf. Control of this pathogen includes use of resistant cucumber cultivars and costly fungicide programs. Continuous use has led to resistance to commonly used fungicides. This has become a major concern and in response, seed companies have developed cucumber cultivars which claim downy mildew resistance.  This study evaluates different cucumber cultivars and assesses their level of resistance to CDM. The results indicate that an integrated management approach of reduced fungicide application and the use of resistant cultivars can suppress levels of CDM and yield a cucumber crop. Additionally, a molecular study was conducted, comparing the relative expression of genes encoding a basic PR-1 protein, a cytosolic ascorbate peroxidase protein and three resistance (R) gene proteins, in nineteen cultivars. All of the selected genes were analyzed using real-time PCR. The relative expression levels of the R-genes varied between cultivars. The basic PR-1 protein decreased expression in the majority of the cultivars, suggesting no involvement in the first twenty-four hours. Cytosolic ascorbate peroxidase relative expression levels suggest an increase in susceptible cultivars and a decrease in tolerant cultivars.en
dc.description.degreeMaster of Scienceen
dc.format.mediumETDen
dc.identifier.othervt_gsexam:114en
dc.identifier.urihttp://hdl.handle.net/10919/49606en
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectcucurbit downy mildewen
dc.subjectcucumberen
dc.subjectCSA 06724en
dc.subjectcyazofamiden
dc.subjectfluopicolideen
dc.subjectPR-1en
dc.subjectcytosolic ascorbate peroxidaseen
dc.subjectCSA06758en
dc.subjectCSA06757en
dc.titleCucurbit Downy Mildew (Pseudoperonospora cubensis): Cucumber Resistanceen
dc.typeThesisen
thesis.degree.disciplinePlant Pathology, Physiology, and Weed Scienceen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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