title: Enhancing resistance to Sclerotinia minor in peanut by expressing a barley oxalate oxidase gene.
abstract: Sclerotinia minor Jagger is the causal agent of Sclerotinia blight, a highly destructive disease of peanut (Arachis hypogaea). Based on evidence that oxalic acid is involved in the pathogenicity of many Sclerotinia species, our objectives were to recover transgenic peanut plants expressing an oxalic acid-degrading oxalate oxidase and to evaluate them for increased resistance to S. minor. Transformed plants were regenerated from embryogenic cultures of three Virginia peanut cultivars (Wilson, Perry, and NC-7). A colorimetric enzyme assay was used to screen for oxalate oxidase activity in leaf tissue. Candidate plants with a range of expression levels were chosen for further analysis. Integration of the transgene was confirmed by Southern-blot analysis, and gene expression was demonstrated in transformants by northern-blot analysis. A sensitive fluorescent enzyme assay was used to quantify expression levels for comparison to the colorimetric protocol. A detached leaflet assay tested whether transgene expression could limit lesion size resulting from direct application of oxalic acid. Lesion size was significantly reduced in transgenic plants compared to nontransformed controls (65%-89% reduction at high oxalic acid concentrations). A second bioassay examined lesion size after inoculation of leaflets with S. minor mycelia. Lesion size was reduced by 75% to 97% in transformed plants, providing evidence that oxalate oxidase can confer enhanced resistance to Sclerotinia blight in peanut.
authors.affiliation: Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA.
authors.forename: D Malcolm
authors.initials: DM
authors.lastname: Livingstone
authors.forename: Jaime L
authors.initials: JL
authors.lastname: Hampton
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Phipps
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Grabau
mesh_terms: D010367:Arachis / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000382:microbiology*; D001203:Ascomycota / Q000472:pathogenicity*; D001483:Base Sequence; D018744:DNA, Plant / Q000235:genetics; D005298:Fertility; D015870:Gene Expression; D017343:Genes, Plant; D001467:Hordeum / Q000201:enzymology* / Q000235:genetics*; D019815:Oxalic Acid / Q000494:pharmacology; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D030821:Plants, Genetically Modified; D014170:Transformation, Genetic
chemical_list: D018744:DNA, Plant; D019815:Oxalic Acid; D010088:Oxidoreductases; C020598:oxalate oxidase