Impact of compatible and incompatible barley—Blumeria graminis f.sp. hordei interactions on chlorophyll fluorescence parameters
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Interactions between different barley genotypes and the fungal pathogen Blumeria graminis f.sp. hordei (Bgh) have a specific impact on the crop physiology. Within the context of plant resistance phenotyping, it is relevant to investigate early host–pathogen interactions to avoid the crop infestation. Analyzing different parameters of the photosynthesis apparatus gives in-depth information of the plant’s health status and can be used for a spatial and temporal assessment of interaction types during plant–pathogen infestation. In the present study, experiments were performed with a near-isogenic line of barley cv. Ingrid WT (susceptible), mlo3 (papilla-based resistance) as well as a near-isogenic line of cv. Pallas, containing the Mla1 (hypersensitive response-based resistance) gene. After inoculation with Bgh isolate K1, the leaves were measured daily using chlorophyll fluorescence imaging. Inoculated, susceptible wild-type leaves showed a reduced effective quantum yield of the photosystem II (ΦPSII) already 1 day after inoculation. In accordance with the quantum yield reduction, the non-photochemical quenching (NPQ) increased, indicating thermal dissipation of excess energy. The changes of ΦPSII and NPQ represent modifications of the leaf metabolism to aid the fungal nutrition uptake, which is influenced by Bgh. By analyzing these parameters, it was also possible to indicate resistance reactions of mlo3 and Mla1 barley genotypes against Bgh. During papilla formation in mlo3 leaves, ΦPSII revealed the lowest values. In contrast, inoculated Mla1 leaves showed the lowest NPQ. The present study proofs that chlorophyll fluorescence imaging is a valuable tool for investigating early plant–pathogen interaction noninvasively. Furthermore, this phytopathology study uses chlorophyll fluorescence imaging, chlorophyll extraction and microscopic observations to characterize the interaction response of different genotypes to an Bgh infection.
KeywordsChlorophyll fluorescence imaging Host–pathogen interaction Phenotyping Hordeum vulgare Blumeria graminis f.sp. hordei
This work could be carried out due to the financial support of the German Federal Ministry of Education and Research (BMBF) within the scope of the competitive grants program “Networks of excellence in agricultural and nutrition research—CROP. SENSe.net” (Funding Code: 0315529), junior research group “Hyperspectral phenotyping of resistance reactions of barley” and by funds of the Federal Ministry of Food and Agriculture (BMEL) (Grant No. 2818204615) based on a decision of the Parliament of the Federal Republic of Germany via the Federal Office for Agriculture and Food (BLE) under the innovation support program.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Human and animal rights
This manuscript does not contain any studies with human participants or animals performed by any of the authors.
Informed consent was obtained from all individual participants included in the study.
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