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Doctoral thesis, 2012

Secondary metabolites associated with plant disease, plant defense and biocontrol

Andersson, Pierre


Secondary metabolites of the fungal ash dieback pathogen Hymenoscyphus pseudoalbidus were investigated. Nine steroidal compounds were isolated from, or detected in, liquid cultures of the fungus. Three were the previously known compounds viridiol, viridin and demethoxyviridiol. Six were the previously unreported compounds 1-deoxyviridiol, 1-deoxy-2-demethylviridiol, 3-dihydrovirone, B-norviridin enol, Bnorviridiol lactone and 1β-hydroxy-2α-hydroasterogynin A. All of the compounds are structurally related to each other, although the three latter are B-norsteroids, which are rare in nature. Viridiol displayed phytotoxic activity to seedlings of the natural host Fraxinus excelsior. The amount of damage caused by viridiol was higher on ash seedlings of clones, classed as susceptible to H. pseudoalbidus. The metabolomes of resistant clones of F. excelsior were compared to those of susceptible clones. No differences were detected that were common to all clones within the groups. Metabolomes of ash seedlings treated with viridiol were compared to those of untreated ash seedlings. A number of significant changes in the concentrations of compounds were observed at the clone level. No change common to all resistant or susceptible clones was observed. Secondary metabolites from the bacterial biocontrol agent Pseudomonas brassicacearum MA250 were investigated. The known compounds piliferolide A and SB-253514, as well as, the previously unreported compound piliferoic acid A were isolated from the bacterium. The compounds displayed growth inhibition of the fungal pathogen Microdochium nivale at concentrations down to 180 μM, which indicates that they may contribute to the biocontrol effect of P. brassicacearum MA250 on M. nivale.


Chalara fraxinea; Hymenoscyphus pseudoalbidus; secondary metabolites; steroids; biocontrol; Microdochium nivale; Pseudomonas

Published in

Acta Universitatis Agriculturae Sueciae
2012, number: 2012:52
ISBN: 978-91-576-7699-3
Publisher: Institutionen för kemi, Sveriges lantbruksuniversitet

Authors' information

Andersson, Pierre
Swedish University of Agricultural Sciences, Department of Chemistry

UKÄ Subject classification

Analytical Chemistry
Organic Chemistry

URI (permanent link to this page)