title: Presymptomatic detection of powdery mildew infection in winter wheat cultivars by laser-induced fluorescence.
abstract: The sensor-based monitoring of diseases under controlled conditions establishes an objective tool that allows a better understanding of the pathogen-plant interactions in different situations. The purpose of our work was to implement the presymptomatic detection of powdery mildew  on wheat leaves shortly after fungus inoculation by spectral and time-resolved laser-induced fluorescence spectroscopy. In the general scope of plant phenotyping, we hypothesized that it is possible to discriminate between wheat genotypes that are either resistant or susceptible to powdery  mildew. According to our results, the presymptomatic detection of powdery mildew on wheat leaves was accomplished, irrespective of genotype, as early as one day after inoculation using the fluorescence amplitude ratio F451:F522. Similarly, the ratios F451:F522, F522:F687, and F522:F736 of  the half-bandwidth are also appropriate parameters. Furthermore, in the spectral range between 410 nm and 620 nm, the mean lifetime was significantly longer in inoculated leaves than it was in control leaves. Finally, the short-term (10-12 hour) increase of the fluorescence mean lifetime  at 530 nm and 560 nm following the inoculation suggests that the speed of the plant reaction might be associated to its resistance to the pathogen. Based on this information, we conclude that determinations of ultraviolet, laser-induced fluorescence intensity and lifetime are suitable approaches  to presymptomatically detect powdery mildew on wheat leaves one day after inoculation.
authors.affiliation: University of Bonn, Institute of Crop Science and Resource Conservation-Horticultural Science, Auf dem Huegel 6, D-53121 Bonn, Germany.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Bürling
authors.forename: Mauricio
authors.initials: M
authors.lastname: Hunsche
authors.forename: Georg
authors.initials: G
authors.lastname: Noga
mesh_terms: D000704:Analysis of Variance; D001203:Ascomycota / Q000737:chemistry* / Q000302:isolation & purification; D010641:Phenotype; D010935:Plant Diseases / Q000382:microbiology*; D013050:Spectrometry, Fluorescence / Q000379:methods*; D014908:Triticum / Q000737:chemistry / Q000382:microbiology*