Genetic resistance to Hymenoscyphus pseudoalbidus limits fungal growth and symptom occurrence in Fraxinus excelsior

Abstract Ash dieback, a forest epidemic caused by the invasive fungus Hymenoscyphus fraxineus, threatens ash trees throughout Europe. Within Fraxinus excelsior populations, a small proportion of genotypes show a low susceptibility to the pathogen. We compared the metabolomes from a cohort of low-susceptibility ash genotypes with a cohort of high-susceptibility ash genotypes. This revealed two significantly different chemotypes. A total of 64 candidate metabolites associated with reduced or increased susceptibility in the chemical families secoiridoids, coumarins, flavonoids, phenylethanoids, and lignans. Increased levels of two coumarins, fraxetin and esculetin, were strongly associated with reduced susceptibility to ash dieback. Both coumarins inhibited the growth of H. fraxineus in vitro when supplied at physiological concentrations, thereby validating their role as markers for low susceptibility to ash dieback. Similarly, fungal growth inhibition was observed when the methanolic bark extract of low-susceptibility ash genotypes was supplied. Our findings indicate the presence of constitutive chemical defense barriers against ash dieback in ash.

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Susceptibility of autochthonous German Fraxinus excelsior clones to Hymenoscyphus pseudoalbidus is genetically determined

Annals of Forest Science ◽

10.1007/s13595-014-0413-1 ◽

2014 ◽

Vol 72 (2) ◽

pp. 183-193 ◽

Cited By ~ 19

Author(s):

Rasmus Enderle ◽

Aikaterini Nakou ◽

Kristina Thomas ◽

Berthold Metzler

Keyword(s):

Fraxinus Excelsior ◽

Hymenoscyphus Pseudoalbidus ◽

Genetically Determined

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First Report of the Ash Dieback Pathogen Hymenoscyphus pseudoalbidus (Anamorph Chalara fraxinea) on Fraxinus excelsior in Belgium

Plant Disease ◽

10.1094/pdis-07-10-0540 ◽

2011 ◽

Vol 95 (2) ◽

pp. 220-220 ◽

Cited By ~ 11

Author(s):

A. Chandelier ◽

N. Delhaye ◽

M. Helson

Keyword(s):

Fraxinus Excelsior ◽

Malt Extract ◽

Internal Transcribed Spacer Region ◽

Ash Dieback ◽

Fungal Isolation ◽

First Report ◽

Chalara Fraxinea ◽

Fungal Biology ◽

Hymenoscyphus Pseudoalbidus ◽

Branch Dieback

Since the early 1990s, European ash (Fraxinus excelsior L.) has been affected by a lethal disease caused by the ascomycete fungus, Hymenoscyphus pseudoalbidus, originally known under the name of its anamorph, Chalara fraxinea (2,4). Pathogenicity of H. pseudoalbidus was demonstrated by inoculations on young trees (3). This emerging pathogen induces necrosis of leaf rachises, leaf wilting and shedding, bark necrosis, and wood discoloration as well as shoot, twig, and branch dieback. First observed in Poland, ash dieback now occurs in many parts of Europe. Since 2009, a survey of ash dieback caused by H. pseudoalbidus has been conducted in Wallonia (southern Belgium). Sampling units were selected to take the occurrence of ash stands and the potential points of entry of the pathogen into the country (nurseries, sawmills, rivers, and roads) into account. While the disease was not detected in 2009, young, naturally regenerated trees displaying typical symptoms of ash dieback were found in June 2010 in Silly, a village in the province of Hainaut. Symptomatic trees were located along a road in front of a large ash stand. Examination of shoots with bark necrosis from three symptomatic trees yielded positive results on the basis of a real time PCR test developed in our laboratory for the detection of H. pseudoalbidus (1). To confirm the molecular identification, fungal isolation from discolored wood onto malt extract agar supplemented with 100 mg liter–1 of streptomycin sulfate was attempted. After 18 days at 20 to 22°C in the dark, slow-growing, dull white colonies with gray patches, resembling those of C. fraxinea, had formed. The nuclear ribosomal internal transcribed spacer region (ITS) was amplified with primers ITS1 and ITS4 (4) and partly sequenced (GenBank Accession No. FR667687). A BLASTn search in GenBank revealed that the sequence of the Belgian isolate (452 bp) displayed 100% identity with sequences of a H. pseudoalbidus isolate from Switzerland (GenBank Accession No GU586932). In contrast, the sequence showed some mismatches with that of the closely related and probably strictly saprotrophic fungus, Hymenoscyphus albidus (GenBank Accession No GU586891.1). The strain was deposited as reference material in the Fungal Biology collection (CBS 128012). To our knowledge, this is the first report of ash dieback caused by H. pseudoalbidus in Belgium. The discovery of this aggressive tree pathogen in Wallonia documents its further westward spread in Europe. In the future, we expect that H. pseudoalbidus will continue its range expansion into areas that have so far not been affected by ash dieback. References: (1) A. Chandelier et al. For. Pathol. 40:87, 2010. (2) T. Kowalski. For. Pathol. 36:264, 2006. (3) T. Kowalski and O. Holdenrieder. For. Pathol. 39:1, 2009. (4) V. Queloz et al. For. Pathol. Online publication. doi:10.1111/j.1439-0329.2010.00645.x, 2010.

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The occurrence of Hymenoscyphus pseudoalbidus apothecia in the leaf litter of Fraxinus excelsior stands with ash dieback symptoms in southern Poland

Acta Mycologica ◽

10.5586/am.2013.031 ◽

2013 ◽

Vol 48 (2) ◽

pp. 135-146 ◽

Cited By ~ 8

Author(s):

Tadeusz Kowalski ◽

Maciej Białobrzeski ◽

Agnieszka Ostafińska

Keyword(s):

Leaf Litter ◽

Disease Process ◽

Fraxinus Excelsior ◽

Ash Dieback ◽

Disease Symptoms ◽

Southern Poland ◽

Chalara Fraxinea ◽

Hymenoscyphus Pseudoalbidus

The paper presents the results of a study performed in 28 ash stands located in Myśleniece and Dynów Forest Districts in southern Poland. The intensity of Fraxinus excelsior disease process was estimated based on the disease symptoms analysis of 1400 trees. The amount of infectious material of Hymenoscyphus pseudoalbidus (anamorph Chalara fraxinea) was estimated by the leaf litter examination on 166 square (0.5 × 0.5 m) plots. The total number of ash leaf rachises and apothecia were counted. The analysis shows that the estimated number of H. pseudoalbidus apothecia may reach from 370 thousand to over 13 million per hectare at a time.

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Seasonal Pattern of Lesion Development in Diseased Fraxinus excelsior Infected by Hymenoscyphus pseudoalbidus

PLoS ONE ◽

10.1371/journal.pone.0076429 ◽

2014 ◽

Vol 9 (4) ◽

pp. e76429 ◽

Cited By ~ 16

Author(s):

Stina Barbro Katrin Bengtsson ◽

Pia Barklund ◽

Claudia von Brömssen ◽

Jan Stenlid

Keyword(s):

Seasonal Pattern ◽

Fraxinus Excelsior ◽

Lesion Development ◽

Hymenoscyphus Pseudoalbidus

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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

Phytochemistry ◽

10.1016/j.phytochem.2014.03.005 ◽

2014 ◽

Vol 102 ◽

pp. 115-125 ◽

Cited By ~ 15

Author(s):

M.R. Cleary ◽

P.F. Andersson ◽

A. Broberg ◽

M. Elfstrand ◽

G. Daniel ◽

...

Keyword(s):

Microscopic Study ◽

Fraxinus Excelsior ◽

Ash Dieback ◽

Hymenoscyphus Pseudoalbidus

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Hymenoscyphus pseudoalbidus. [Distribution map].

Distribution Maps of Plant Diseases ◽

10.1079/dmpd/20133421493 ◽

2013 ◽

Author(s):

Keyword(s):

Czech Republic ◽

Northern Ireland ◽

Geographical Distribution ◽

Fraxinus Excelsior ◽

Distribution Map ◽

Central Russia ◽

Hymenoscyphus Pseudoalbidus ◽

Fraxinus Angustifolia ◽

New Distribution ◽

Distribution In Europe

Abstract A new distribution map is provided for Hymenoscyphus pseudoalbidus Queloz et al. Ascomycota: Leotiomycetes: Helotiales. Hosts: common ash (Fraxinus excelsior), narrow-leaved ash (Fraxinus angustifolia). Information is given on the geographical distribution in Europe (Austria, Belgium, Croatia, Czech Republic, Denmark, Estonia, Finland, Aland Islands, Mainland Finland, France, Germany, Hungary, Ireland, Italy, Latvia, Lithuania, Netherlands, Norway, Poland, Romania, Russia, Central Russia, Slovakia, Slovenia, Sweden, Switzerland, UK, Channel Islands, England and Wales, Northern Ireland, Scotland), Asia (Japan).

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