Genotypes of Fraxinus excelsior with different susceptibility to the ash dieback pathogen Hymenoscyphus pseudoalbidus and their response to the phytotoxin viridiol - a metabolomic and microscopic study.
Eight European ash (Fraxinus excelsior) genotypes with different known susceptibility to Hymenoscyphus pseudoalbidus were tested against the phytotoxin viridiol and their response described at the microscopic and metabolomic level. All ash genotypes were sensitive to the toxin and necrosis was detectable after 24h. Among the three viridiol concentrations used in the experiment, the lowest concentration (14.7μM) yielded markedly lower mean damage scores compared to those resulting from seedlings tested at higher dosages. The highest damage scores were associated with the susceptible ash clones S-101, S-106 and S-125, but also with resistant clone R-104. Three resistant clones (R-131, R-121, and R-118) had lower mean damage scores compared to susceptible clones. Wilting of leaves was more common 48h after treatment and more pronounced on seedlings with high damage scores. The resulting lesions generally lacked browning of tissue and displayed only surface disruption of cells in direct contact with the toxin. A delay in symptom development was evident on all five resistant clones tested with the two higher concentrations of viridiol. LC-HRMS and MS/MS analyses of ash seedling extracts suggest several secoiridoid compounds as well as compounds related to abscisic acid (ABA) to be produced in response to viridiol. ABA-cysteine and xanthoxin were found at significantly higher concentrations in susceptible clones compared to resistant clones after treatment with viridiol, suggesting a primary role of ABA in response to stress. The results observed in this study suggest that genetic resistance to H. pseudoalbidus among ash genotypes may be explained, in part, by the varied response to phytotoxins produced by the fungus.
Department of Forest Mycology and Plant Pathology, Uppsala BioCenter, Swedish University of Agricultural Sciences, Almas allé 5, PO Box 7026, SE-750 07 Uppsala, Sweden. Electronic address: Michelle.Cleary@slu.se.
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Cleary
Department of Chemistry and Biotechnology, Uppsala BioCenter, Swedish University of Agricultural Sciences, Almas allé 5, PO Box 7015, SE-750 07 Uppsala, Sweden.
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Andersson
Department of Chemistry and Biotechnology, Uppsala BioCenter, Swedish University of Agricultural Sciences, Almas allé 5, PO Box 7015, SE-750 07 Uppsala, Sweden.
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Broberg
Department of Forest Mycology and Plant Pathology, Uppsala BioCenter, Swedish University of Agricultural Sciences, Almas allé 5, PO Box 7026, SE-750 07 Uppsala, Sweden.
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Elfstrand
Department of Forest Products, Swedish University of Agricultural Sciences, Vallvägen 9C, PO Box 7008, 750-07 Uppsala, Sweden.
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Daniel
Department of Forest Mycology and Plant Pathology, Uppsala BioCenter, Swedish University of Agricultural Sciences, Almas allé 5, PO Box 7026, SE-750 07 Uppsala, Sweden.
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Stenlid
D000734:Androstenediols / Q000494:pharmacology*; D001203:Ascomycota / Q000472:pathogenicity / Q000502:physiology*; D031661:Fraxinus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D014644:Genetic Variation / Q000187:drug effects; D005838:Genotype; D055432:Metabolomics; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D053719:Tandem Mass Spectrometry
D000734:Androstenediols; C055608:viridiol
Fraxinus excelsior; Hymenoscyphus pseudoalbidus; Metabolome; Phytotoxin; Viridiol