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| Oidium | |
|---|---|
| Name | Oidium |
| Regnum | Fungi |
| Divisio | Ascomycota |
| Classis | Leotiomycetes |
| Ordo | Erysiphales |
| Familia | Erysiphaceae |
| Genus | Oidium (sensu lato) |
| Subdivision ranks | Species |
Oidium is a historical and morphological term applied to asexual, powdery superficial fungal stages described across multiple genera within the order Erysiphales. It has been used in plant pathology, mycology, and agricultural literature to denote conidial stages implicated in widespread foliar diseases, with nomenclatural revisions linking many occurrences to teleomorphic genera and to institutions of plant health and crop research. The concept has influenced diagnostic practice in extension services, quarantine agencies, and phytopathological research.
The name has roots in classical mycological works and in revisions by authors associated with Persoon, Elias Magnus Fries, and later monographers such as Anton de Bary and Joseph Lister-era mycologists. Historically treated as a form genus for anamorphs, the designation appeared in protologues published in journals tied to Royal Society-associated periodicals and in compilations maintained by botanical gardens like Kew Gardens and herbaria at Royal Botanic Gardens, Kew. Modern taxonomic practice governed by the International Code of Nomenclature for algae, fungi, and plants and molecular systematics research using loci such as ITS and LSU rDNA has reassigned many entities to teleomorph genera including Erysiphe, Sphaerotheca, Podosphaera, Phyllactinia, and Leveillula, a process reflected in monographs from institutions like USDA laboratories and university departments at University of California, Davis and Université Paris-Saclay.
Authors and collections cited in revisions include curators at Smithsonian Institution, members of the American Phytopathological Society, and taxonomists associated with the Royal Botanic Gardens, Kew database. The shift from dual nomenclature to one-name nomenclature influenced lists produced by entities such as the International Mycological Association and regional plant protection organizations like European and Mediterranean Plant Protection Organization.
Anamorphic stages described under the name are characterized by chains of conidia produced on superficial mycelium, often associated with asexual structures observed under light microscopes used in laboratories at Johns Hopkins University and ETH Zurich. Conidia morphology, germination behavior, and attachment involve interactions studied in labs affiliated with Max Planck Society and experiments performed at experimental stations such as those at Iowa State University and Wageningen University. Life cycles typically include obligate parasitism, formation of haustoria in host epidermal cells (documented in microscopy work from University of Cambridge), and seasonally produced sexual fruiting bodies in teleomorphic stages observed by researchers at Cornell University and Institut National de la Recherche Agronomique.
Molecular phylogenetic analyses by groups at University of Minnesota, Heinrich Heine University Düsseldorf, and University of Tokyo employ sequences deposited in databases curated by GenBank and computational pipelines implemented using tools from projects like EMBL-EBI and NCBI.
Anamorphic forms historically assigned to this name have been reported as pathogens on a vast array of hosts including economically important genera studied by Clemson University extension, such as Vitis vinifera (grapevine), Triticum aestivum (wheat), Malus domestica (apple), Cucumis sativus (cucumber), and ornamentals cultivated in institutions like Royal Horticultural Society gardens. Reports and surveys produced by national agencies including USDA APHIS, DEFRA, and regional research stations at CSIRO document occurrence on native and introduced plants, with host specificity ranging from narrow-host specialists to broad-host generalists documented in bulletins from FAO and monographs from International Rice Research Institute.
Cross-infection experiments reported by teams at Michigan State University and Ohio State University have evaluated host range on crops catalogued by Food and Agriculture Organization panels, while historical herbarium specimens at New York Botanical Garden and The Field Museum preserve records of early outbreaks.
Infected tissues typically show superficial white to gray powdery colonies on leaves, stems, flowers, or fruit surfaces—symptoms recorded in extension fact sheets from University of Florida and illustrated in guides from Royal Horticultural Society. Diagnosis integrates morphological microscopy protocols endorsed by American Phytopathological Society and molecular assays developed by laboratories at USDA ARS and universities such as Penn State University and University of Illinois Urbana-Champaign. Techniques include light microscopy of conidial chains, scanning electron microscopy from facilities at ETH Zurich, and PCR-based detection using primers validated in studies published in journals like Phytopathology and Mycologia.
Differential diagnosis with other foliar pathogens observed by plant clinics at University of Wisconsin–Madison and Kansas State University often involves ruling out Botrytis cinerea, Alternaria alternata, and abiotic disorders using protocols from diagnostic labs at North Carolina State University.
Epidemiological patterns have been characterized in crops and wild ecosystems monitored by agencies like USDA, FAO, and regional plant protection organizations including European and Mediterranean Plant Protection Organization. Dispersal typically occurs via wind-borne conidia, with microclimate factors studied by ecologists at University of British Columbia and Monash University influencing infection cycles. Climate change impacts on phenology and range shifts have been modeled by teams at IPCC-contributing institutions and in landscape-scale studies conducted by Wageningen University & Research and CSIRO.
Epidemics on monoculture plantations documented in reports from Cargill supply-chain audits and outbreaks affecting grapevines reported by International Organisation of Vine and Wine illustrate interactions among agronomy, cultivar susceptibility, and regional weather patterns tracked by services such as European Centre for Medium-Range Weather Forecasts.
Integrated management strategies recommended by extension services at University of California Cooperative Extension, Penn State Extension, and CABI include cultivar resistance screening conducted by breeding programs at Institut National de la Recherche Agronomique and chemical controls evaluated by researchers at University of Bologna and Aarhus University. Fungicide classes such as demethylation inhibitors and QoI compounds tested in trials at Rothamsted Research and North Carolina State University must be rotated to delay resistance emergence described in studies from Syngenta and regulatory assessments by European Food Safety Authority.
Cultural practices—training and pruning guides from Royal Horticultural Society—and biocontrol research by groups at Murdoch University and University of Sydney explore antagonists and induced resistance approaches. Quarantine measures and certification schemes administered by USDA APHIS and EPPO aim to limit spread through nursery trade and germplasm exchanges coordinated with institutions like International Potato Center.
Historic and contemporary outbreaks have caused yield and quality losses documented in economic analyses by World Bank, FAO, and national ministries of agriculture such as those in India and China. Costs include fungicide expenditures tracked in industry reports by Corteva Agriscience and market impacts reported by commodity organizations like International Grains Council and OIV (International Organisation of Vine and Wine). Research investments at universities including Iowa State University and University of California, Davis and policy responses by agencies such as USDA reflect the importance of accurate identification and integrated management to protect food security and horticultural industries.
Category:Fungal plant pathogens and diseases