Abstract
Differences in early plant-pathogen interactions are mainly characterized by using destructive methods. Optical sensors are advanced techniques for phenotyping host-pathogen interactions on different scales and for detecting subtle plant resistance responses against pathogens. A microscope with a hyperspectral camera was used to study interactions between Blumeria graminis f. sp. hordei and barley (Hordeum vulgare) genotypes with high susceptibility or resistance due to hypersensitive response (HR) and papilla formation. Qualitative and quantitative assessment of pathogen development was used to explain changes in hyperspectral signatures. Within 48 h after inoculation, genotype-specific changes in the green and red range (500 to 690 nm) and a blue shift of the red-edge inflection point were observed. Manual analysis indicated resistance-specific reflectance patterns from 1 to 3 days after inoculation. These changes could be linked to host plant modifications depending on individual host-pathogen interactions. Retrospective analysis of hyperspectral images revealed spectral characteristics of HR against B. graminis f. sp. hordei. For early HR detection, an advanced data mining approach localized HR spots before they became visible on the RGB images derived from hyperspectral imaging. The link among processes during pathogenesis and host resistance to changes in hyperspectral signatures provide evidence that sensor-based phenotyping is suitable to advance time-consuming and cost-expensive visual rating of plant disease resistances.
Highlights
Blumeria graminis f. sp. hordei and barley (Hordeum vulgare) genotypes with high susceptibility or resistance due to hypersensitive response (HR)
For early HR detection, an advanced data mining approach localized HR spots before they became visible on the RGB images derived from hyperspectral imaging
Dysfunction of the H. vulgare mildew locus o gene triggers the formation of effective cell wall appositions at sites of B. graminis f. sp. hordei penetration sites during the first approximately 40 h after inoculation and inhibit penetration (Jørgensen 1992; Röpenack et al 1998)
Summary
Blumeria graminis f. sp. hordei and barley (Hordeum vulgare) genotypes with high susceptibility or resistance due to hypersensitive response (HR). Manual analysis indicated resistance-specific reflectance patterns from 1 to 3 days after inoculation These changes could be linked to host plant modifications depending on individual host–pathogen interactions. Dysfunction of the H. vulgare mildew locus o (mlo) gene triggers the formation of effective cell wall appositions (papillae) at sites of B. graminis f. Hordei penetration sites during the first approximately 40 h after inoculation (hai) and inhibit penetration (Jørgensen 1992; Röpenack et al 1998) This papilla formation is based on fast and high local accumulations of callose, arabinoxylan, polysaccharides, ferulic acid, and cellulose (Chowdhury et al 2014). H. vulgare lines and cultivars with a B. graminis f. sp. hordei racespecific resistance mildew locus a (Mla) gene are characterized by a fast, single-cell hypersensitive response (HR) to B. graminis f. sp
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