scholarly journals Estimating mortality rates of European ash ( Fraxinus excelsior ) under the ash dieback ( Hymenoscyphus fraxineus ) epidemic

2018 ◽  
Vol 1 (1) ◽  
pp. 48-58 ◽  
Author(s):  
Tim L. R. Coker ◽  
Jiří Rozsypálek ◽  
Anne Edwards ◽  
Tony P. Harwood ◽  
Louise Butfoy ◽  
...  
Keyword(s):  
Mortality Rates ◽  
Fraxinus Excelsior ◽  
Ash Dieback ◽  
Hymenoscyphus Fraxineus ◽  
European Ash

scholarly journals Amplifying feedback loop between growth and wood anatomical characteristics of Fraxinus excelsior explains size-related susceptibility to ash dieback

2020 ◽  
Author(s):  
Stefan Klesse ◽  
Georg von Arx ◽  
Martin M Gossner ◽  
Christian Hug ◽  
Andreas Rigling ◽  
...  
Keyword(s):  
Landscape Heterogeneity ◽  
Turgor Pressure ◽  
Ring Width ◽  
Mortality Rates ◽  
Data Availability ◽  
Fraxinus Excelsior ◽  
Ash Dieback ◽  
Vessel Size ◽  
Hymenoscyphus Fraxineus ◽  
Crown Dieback

Abstract Since the 1990s the invasive fungus Hymenoscyphus fraxineus has caused severe crown dieback and high mortality rates in Fraxinus excelsior in Europe. In addition to a strong genetic control of tolerance to the fungus, previous studies have found landscape heterogeneity to be an additional driver of variability in the severity of dieback symptoms. However, apart from climatic conditions related to heat and humidity influencing fungal infection success, the mechanistic understanding of why smaller or slower-growing trees are more susceptible to dieback remains less well understood. Here, we analyzed three stands in Switzerland with a unique setting of 8 years of data availability of intra-annual diameter growth and annual crown health assessments. We complemented this by ring width and quantitative wood anatomical measurements extending back before the monitoring started to investigate if wood anatomical adjustments can help better explain the size-related dieback phenomenon. We found that slower-growing trees or trees with smaller crowns already before the arrival of the fungus were more susceptible to dieback and mortality. Defoliation directly reduced growth as well as maximum earlywood vessel size, and the positive relationship between vessel size and growth rate caused a positive feedback amplifying and accelerating crown dieback. Measured non-structural carbohydrate (NSC) concentrations in the outermost five rings did not significantly vary between healthy and weakened trees, which translate into large differences in absolute available amount of NSCs. Thus, we hypothesize that a lack of NSCs (mainly sugars) leads to lower turgor pressure and smaller earlywood vessels in the following year. This might impede efficient water transport and photosynthesis, and be responsible for stronger symptoms of dieback and higher mortality rates in smaller and slower-growing trees.

scholarly journals Decline of Fraxinus excelsior L. in parks of Saint Petersburg: Who is to blame – Hymenoscyphus fraxineus or Diplodia spp.?

2020 ◽  
Vol 73 (1) ◽  
pp. 43-51
Author(s):  
Dmitrii A. Shabunin ◽  
Andrey V. Selikhovkin ◽  
Elena Yu. Varentsova ◽  
Dmitry L. Musolin
Keyword(s):  
Light Microscopy ◽  
Fraxinus Excelsior ◽  
Ash Dieback ◽  
Saint Petersburg ◽  
Hymenoscyphus Fraxineus ◽  
Ash Trees ◽  
Fallen Leaves ◽  
European Ash

Abstract The weakening and decline of European ash Fraxinus excelsior L. and other ash species have been recorded at different locations in the suburbs of Saint Petersburg, Russia. During the summer of 2019 and spring of 2020, samples from leaves, petioles, and shoots were collected from the weakened and declining ash trees in three parks in Pushkin and Gatchina and maintained in humid chambers to induce the fructification of fungi. In total, 30 taxa of micromycetes belonging to 23 genera were identified using methods of light microscopy. Hymenoscyphus fraxineus, a putative agent of ash dieback, was not recorded in the samples collected in the crowns of trees, but only on the petioles of the fallen leaves in spring. Out of all the micromycetes recorded, only coelomycetes from the genus Diplodia Fr. (in particular, D. mutila) can damage the branches of ash trees and, thus, be considered pathogenic. It is likely that H. fraxineus opens “the entry of infection” and Diplodia spp. cause the major weakening and decline of branches. The data obtained can significantly change our understanding of the causes of ash dieback and possible methods of ash stand preservation. The reason for the low pathogenicity and activity of H. fraxineus, as well as the possible role of ascomycetes Diplodia spp. in the dieback of ash stands requires further research.

scholarly journals Transformation of European Ash (Fraxinus excelsior L.) Callus as a Starting Point for Understanding the Molecular Basis of Ash Dieback

Plants ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2524
Author(s):  
Anna Hebda ◽  
Aleksandra Liszka ◽  
Piotr Zgłobicki ◽  
Katarzyna Nawrot-Chorabik ◽  
Jan J. Lyczakowski
Keyword(s):  
Molecular Basis ◽  
Selection Process ◽  
Pathogenic Fungus ◽  
Fraxinus Excelsior ◽  
Reporter System ◽  
Ash Dieback ◽  
Gus Reporter ◽  
Hymenoscyphus Fraxineus ◽  
Starting Point ◽  
European Ash

The population of European ash (Fraxinus excelsior L.) is currently facing the risk of collapse, mainly due to ash dieback, a disease caused by a pathogenic fungus, Hymenoscyphus fraxineus. To facilitate studies into the molecular basis of ash dieback and design breeding strategies for a generation of resistant trees, it is necessary to develop tools enabling the study of gene function in F. excelsior. Despite this, a method for the genetic engineering of F. excelsior is still missing. Here, we report the first successful genetic transformation of F. excelsior callus and a selection process enabling the formation of stable transgenic callus lines. The protocol relies on the use of Agrobacterium tumefaciens to transform callus tissue derived from embryos of F. excelsior. In our experiments, we used the β-glucuronidase (GUS) reporter system to demonstrate the transformation of callus cells and performed RT-PCR experiments to confirm the stable expression of the transgene. Since ash dieback threatens the long-term stability of many native F. excelsior populations, we hope that the transformation techniques described in this manuscript will facilitate rapid progress in uncovering the molecular basis of the disease and the validation of gene targets previously proposed to be linked to the resistance of trees to H. fraxineus pathogenicity.

scholarly journals Mycobiome of Fraxinus excelsior With Different Phenotypic Susceptibility to Ash Dieback

2021 ◽  
Vol 4 ◽  
Author(s):  
Marta Agostinelli ◽  
Diem Nguyen ◽  
Johanna Witzell ◽  
Michelle Cleary
Keyword(s):  
Large Scale ◽  
Population Decline ◽  
Keystone Species ◽  
Fungal Species ◽  
Fraxinus Excelsior ◽  
Fungal Communities ◽  
Ash Dieback ◽  
Hymenoscyphus Fraxineus ◽  
Ash Trees ◽  
European Ash

For the last two decades, large-scale population decline of European ash (Fraxinus excelsior) has occurred in Europe because of the introduction of the alien fungal pathogen, Hymenoscyphus fraxineus, from East Asia. Since European ash is a keystone species having critical importance for biodiversity, and only a small percentage of the ash population appears to show some tolerance against the pathogen, the loss of ash trees means that other associated organisms, especially those with high or obligate associations to ash, are at risk of further species declines. In this study, we used high throughput DNA sequencing and multivariate analysis to characterize: (i) the mycobiome in aerial tissues (i.e., leaf, bark, and xylem) of ash trees showing different phenotypic response to ash dieback, (ii) the temporal variation in fungal communities across the growing season, and (iii) the similarity in fungal community structure between ash and other common trees species that may serve as an ecological niche substitute for ash microfungi. Results showed that fungal communities differed among the three tissue types, susceptibility classes, in time and between sites. Trophic analysis of functional groups using the FUNGuild tool indicated a higher presence of pathotrophic fungi in leaves than in bark and xylem. The share of pathotrophic fungi increased along a gradient of low to high disease susceptibility in both bark and xylem tissue, while the proportion of symbiotrophic fungi correspondingly decreased in both tissue types. Neighboring, alternative host trees did not share all the fungal species found in ash, however, most microfungi uniquely associated to ash in this study are generalists and not strictly host specific. The progressive disappearance of ash trees on the landscape imposes a high risk for extinction of Red-listed macrofungal species, and breeding for resistance against ash dieback should help sustain important biodiversity associated to ash. Microfungal diversity though may be less prone to such demise since most ash-associated endophytes appear to occur on a broad range of host species.

scholarly journals Situation and perspectives of European ash (Fraxinus spp.) in Ukraine: focus on eastern border

2019 ◽  
Vol 25 (2) ◽  
pp. 193-202
Author(s):  
Kateryna V Davydenko ◽  
Valentyna Borysova ◽  
Olena Shcherbak ◽  
Yevhen Kryshtop ◽  
Valentyna Meshkova
Keyword(s):  
Pathogenic Fungus ◽  
Total Mortality ◽  
Fraxinus Excelsior ◽  
Bacterial Disease ◽  
Eastern Region ◽  
Ash Dieback ◽  
Epicormic Shoots ◽  
Hymenoscyphus Fraxineus ◽  
Ash Trees ◽  
European Ash

The health condition of European ash (Fraxinus excelsior) stands in Ukraine has become worse since 2006. Firstly, in 2011 an alien invasive pathogenic fungus Hymenoscyphus fraxineus was identified in the eastern part of the country and, subsequently, its presence was confirmed in the western and central parts. The aims of our research were to evaluate the health of ash trees and identify the main causes of ash decline in different regions of Ukraine with emphasis on ash dieback and its association with collar rots.    Results showed that since 2013 the number of trees with ash dieback symptoms has been gradually increasing, reaching up to 92 % in 2018. Total mortality due to ash dieback was up to 9 % in 2018. Disease intensity remains high in northern and central Ukraine comparing with the east. Branch dieback, collar rots, epicormic shoots and bacterial disease of ash occurred more often in the eastern region, some symptoms were observed simultaneously. Ash bark beetle galleries, as well as foliage browsing insects, were found mostly in weakened and/or dying trees.    It was indicated that collar rots significantly increase the mortality of ash trees. Armillaria spp. fungi were found to be frequently associated with ash dieback on living stems and fallen trees in 2017, causing high rates of mortality in the northern and central regions. For further ash conservation and breeding programmes, resistant trees in severely damaged regions should be selected to preserve genetic diversity in ash populations.                                                       Keywords: Fraxinus excelsior, ash dieback, collar rot, bacterial disease, epicormic shoots, Hymenoscyphus fraxineus, Armillaria spp.

scholarly journals Ash dieback and contributing factors of forest weakening in provenance tests in the Sumy region

2021 ◽  
Vol 67 (2) ◽  
pp. 113-121
Author(s):  
Valentyna Meshkova ◽  
Viacheslav Samoday ◽  
Kateryna Davydenko
Keyword(s):  
Condition Index ◽  
Health Condition ◽  
Fraxinus Excelsior ◽  
Forest Steppe ◽  
Special Focus ◽  
Contributing Factors ◽  
Ash Dieback ◽  
Collar Rot ◽  
Hymenoscyphus Fraxineus ◽  
European Ash

Abstract The aim of this study was to evaluate the health condition of Fraxinus excelsior L. in provenance tests, with special focus on ash dieback (ADB), but taking into account also other causes of its decline. The research was carried out in the provenance tests of F. excelsior in the forest-steppe part of the Sumy region. ADB symptoms were revealed in all provenance tests. For 2012–2019 the health condition index, ADB incidence and severity increased for all provenances except the Steppe. Collar rot was present in all ash provenances. Fungi species were isolated from the stem parts of ash at all provenances. Hymenoscyphus fraxineus induced longest necrotic lesions following wound inoculation of stems of 7–10-years-old plants of European ash in the forest while inoculation with both Cytospora sp. and Diplodia sp. resulted in smaller necroses. The conclusion from other regions about the coincidence the damage of European ash by ADB and collar rots as well as the coincidence the damage of European ash by collar rot and tree colonization by Hylesinus crenatus (Fabricius, 1787) is supported.

scholarly journals Rising out of the ashes: additive genetic variation for susceptibility to Hymenoscyphus fraxineus in Fraxinus excelsior

2015 ◽  
Author(s):  
F. Muñoz ◽  
B. Marçais ◽  
J. Dufour ◽  
A. Dowkiw
Keyword(s):  
Genetic Variation ◽  
Fraxinus Excelsior ◽  
Narrow Sense ◽  
Narrow Sense Heritability ◽  
Ash Dieback ◽  
Family Effects ◽  
Hymenoscyphus Fraxineus ◽  
Natural Range ◽  
Spatio Temporal ◽  
Crown Dieback

AbstractSince the early 1990s, ash dieback due to the invasive ascomycete Hymenoscyphus fraxineus is threatening Fraxinus excelsior in most of its natural range. Previous studies reported significant levels of genetic variability for susceptibility in F. excelsior either in field or inoculation experiments. The present study was based on a field experiment planted in 1995, fifteen years before onset of the disease. Crown and collar status were monitored on 788 trees from 23 open-pollinated progenies originating from 3 French provenances. Susceptibility was modeled using a Bayesian approach where spatio-temporal effects were explicitly taken into account. Moderate narrow-sense heritability was found for Crown Dieback (CD, h2=0.42). This study is first to show that Collar Lesions are also heritable (h2=0.49 for prevalence and h2=0.42 for severity) and that there is significant genetic correlation (r=0.40) between the severities of both symptoms. There was no evidence for differences between Provenances. Family effects were detected, but computing Individual Breeding Values (IBV) showed that most of the genetic variation lies within families. In agreement with previous reports, early flushing correlates with better crown status. Consequences of these results in terms of management and breeding are discussed.

scholarly journals Soil pH and Organic Matter Content Affects European Ash (Fraxinus excelsior L.) Crown Defoliation and Its Impact on Understory Vegetation

Forests ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 22 ◽  
Author(s):  
Krzysztof Turczański ◽  
Paweł Rutkowski ◽  
Marcin K. Dyderski ◽  
Dorota Wrońska-Pilarek ◽  
Mirosław Nowiński
Keyword(s):  
Organic Matter ◽  
Soil Ph ◽  
Organic Matter Content ◽  
Understory Vegetation ◽  
Fraxinus Excelsior ◽  
Soil Parameters ◽  
Alkaline Soil ◽  
Ash Dieback ◽  
Crown Defoliation ◽  
European Ash

European ash (Fraxinus excelsior L.) dieback caused by the fungus Hymenoscyphus fraxineus (T. Kowalski) Baral, Queloz, and Hosoya has been affecting European forests since 1992. The disease drives severe crown defoliation, branch loss, and finally tree mortality in European ash. The environmental factors affecting the disease process are still not fully recognized. We hypothesized that the level of crown defoliation in ash, as well as its impact on understory vegetation, will differ along the pH gradient in soil. We examined 27 ash stands in western Poland. We assessed the crown defoliation of 15 dominant and co-dominant trees, soil parameters (pH and soil organic matter contents; SOM), and also recorded the understory vegetation species composition. Most moderately and severely damaged trees occurred within the plots with a high SOM content (>7.5%) and neutral to slightly alkaline soil pH (>7.0) in the A horizon. We noted significantly lower crown defoliation in mesic sites with acidic soils and lower SOM contents. The results also showed the influence of ash crown defoliation on the species functional composition. Ash dieback led to the creation of gaps, and their colonization by other species frequently found in forest sites, especially forest-edge tall herbs.

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