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Detection, identification, and quantification of fungal diseases of sugar beet leaves using imaging and non-imaging hyperspectral techniques Inaugural-Dissertation zur

Detection, identification, and quantification of fungal diseases of sugar beet leaves using imaging and non-imaging hyperspectral techniques Inaugural-Dissertation zur

Detection of biotic stress (Venturia inaequalis) in apple trees using hyperspectral data: Non-parametric statistical approaches and physiological implications

Hyperspectral indices to diagnose leaf biotic stress of apple plants, considering leaf phenology

Hyperspectral imaging for small-scale analysis of symptoms caused by different sugar beet diseases Anne-Katrin Mahlein * , Ulrike Steiner, Christian Hillnhütter, Heinz-Wilhelm Dehne and Erich-Christian Oerke Hyperspectral imaging (HSI) offers high potential as a non-invasive diagnostic tool for disease detection. In this paper leaf characteristics and spectral reflectance of sugar beet leaves diseased with Cercospora leaf spot, powdery mildew and leaf rust at different development stages were connected. Light microscopy was used to describe the morphological changes in the host tissue due to pathogen colonisation. Under controlled conditions a hyperspectral imaging line scanning spectrometer (ImSpector V10E) with a spectral resolution of 2.8 nm from 400 to 1000 nm and a spatial resolution of 0.19 mm was used for continuous screening and monitoring of disease symptoms during pathogenesis. A pixel-wise mapping of spectral reflectance in the visible and near-infrared range enabled the detection and detailed description of diseased tissue on the leaf level. Leaf structure was linked to leaf spectral reflectance patterns. Depending on the interaction with the host tissue, the pathogens caused diseasespecific spectral signatures. The influence of the pathogens on leaf reflectance was a function of the developmental stage of the disease and of the subarea of the symptoms. Spectral reflectance in combination with Spectral Angle Mapper classification allowed for the differentiation of mature symptoms into zones displaying all ontogenetic stages from young to mature symptoms. Due to a pixel-wise extraction of pure spectral signatures a better understanding of changes in leaf reflectance caused by plant diseases was achieved using HSI. This technology considerably improves the sensitivity and specificity of hyperspectrometry in proximal sensing of plant diseases.

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the sense that, in the former new vector variables that define the axes of greatest variability in the data are created, while in the latter the original variables that best describe differences between given groups are identified. Strachan et al. (2002) taking reflectance measurements nine times during crop growth found that though individual reflectance-based indices demonstrated the relative differences between application rates and identified both nitrogen and water stresses at various times in the growing season, no single index was able to describe the status of the corn crop throughout the season.. It is essential to find the most optimum narrowbands and hyperspectral indices to discriminate between different levels of stresses. In this we have considered the nutrient stress, water stress and disease stress. We also included the discrimination between varieties, considering it as a genetic stress.