Canditate metabolites for ash dieback tolerance in Fraxinus excelsior

2020 ◽  
Vol 71 (19) ◽  
pp. 6074-6083 ◽  
Author(s):  
Miguel Nemesio-Gorriz ◽  
Riya C Menezes ◽  
Christian Paetz ◽  
Almuth Hammerbacher ◽  
Marijke Steenackers ◽  
...  
Keyword(s):  
Fungal Growth ◽  
Fraxinus Excelsior ◽  
Bark Extract ◽  
High Susceptibility ◽  
Ash Dieback ◽  
Hymenoscyphus Fraxineus ◽  
Ash Trees ◽  
Fungal Growth Inhibition ◽  
Increased Susceptibility

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.

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 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 Parastā oša Fraxinus Excelsior L. destrukcija Latvijā: audžu sukcesija un oša atjaunošanās = Dieback of common ash Fraxinus Excelsior L. in Latvia: species succession and ash regeneration

2020 ◽  
Author(s):  
◽  
Ilze Matisone ◽  
Keyword(s):  
Western Europe ◽  
Health Condition ◽  
Fraxinus Excelsior ◽  
Mixed Stands ◽  
Ash Dieback ◽  
Factors Affecting ◽  
Stand Management ◽  
Species Succession ◽  
Hymenoscyphus Fraxineus ◽  
Ash Trees

The area of common ash forest is only 1–2% of the total forest area in Europe and 0.3% in Latvia. Prior to dieback, ash was an economically and still is ecologically highly important tree species. In Eastern Europe since the beginning of the 1990s, and a decade later throughout Central and Western Europe, rapid dieback of ash stands caused by an unknown reason was observed. In 2006 the causal agent of ash dieback – an anamorphic fungus Hymenoscyphus fraxineus (species name later refined) was determined. In Latvia, intensive dieback of ash stands has been observed since 2000. The aim of the thesis was to assess the dieback dynamics of common ash Fraxinus excelsior L. stands and determine the main factors affecting susceptibility of the trees, as well as future succession and potential regeneration of the affected common ash stands in Latvia. In Latvia, The area of young ash stands decreased by 4.4 times during 2000–2015. The ten-year-inventory (2005–2015) revealed that the overall mortality of ash was 6.9% and standing volume of ash stands decreased by 171 m3 ha–1. The obtained results indicated that regeneration of ash saplings in ash young stands as well as in mature stands was lower than in in the pre-dieback times, but regeneration was still successful. Furthermore, survival and health condition of ash saplings was relatively poor, as only ca. ⅓ of individuals were healthy, and the health condition decreased with aging. Overgrowth of ash stands with shrub species has begun, suggesting formation of broadleaved stands with a small admixture of ash in the future. We found that, susceptibility to ash dieback is significantly affected by morphometric parameters of ash trees and stands, site conditions and meteorological factors. In Latvia, ash dieback was present in ash stands of all ages and composition, yet some individual and regional differences were observed. Lower susceptibility to ash dieback was observed for older/larger dimensions trees, mixed stands on well-drained and dry mineral soils, stands thinned more intensively, and in the eastern part of Latvia. The findings of the thesis are applicable for the planning of ash stand management, assessment of the existing situation, for the designation of additional genetic resource forests, as well as provide basic information for future studies.

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 Marker-Trait Associations for Tolerance to Ash Dieback in Common Ash (Fraxinus excelsior L.)

Forests ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1083
Author(s):  
Rajiv Chaudhary ◽  
Tilman Rönneburg ◽  
Matilda Stein Åslund ◽  
Karl Lundén ◽  
Mikael Brandström Durling ◽  
...  
Keyword(s):  
Disease Severity ◽  
Genotypic Variation ◽  
Tree Breeding ◽  
Mixed Linear Model ◽  
Snp Markers ◽  
Fraxinus Excelsior ◽  
Single Nucleotide ◽  
Ash Dieback ◽  
Hymenoscyphus Fraxineus ◽  
Ash Trees

Common ash (Fraxinus excelsior L.) is a tree species of significant ecological and economic importance that has suffered a devastating decline since the 1990s in Europe. Native ash species are being threatened by the alien invasive fungus Hymenoscyphus fraxineus, which causes ash dieback. The main goal of the study was to develop markers for traits related to tolerance to ash dieback and to investigate whether genotypes selected for tolerance were genetically different from susceptible wild populations. We phenotyped 326 ash trees from Sweden for disease severity and genotyped them using 63 amplicon-derived single-nucleotide polymorphism (SNP) markers derived from genes in 40 scaffolds spanning 8 MB in total, which represents approximately 1% of the ash genome. We used a mixed linear model to test for an association between genotypic variation at these loci and disease severity of ash. In total, two SNPs were found to have significant associations. One non-synonymous SNP associated with the disease severity of ash was found in a gene predicted to encode a subtilisin-related peptidase S8/S53 domain. A second marginally significant marker was associated with an LRR gene. Our results demonstrate an inexpensive time-effective method for generating genomic data that could have potential for use in future tree breeding programs and provide information for marker-assisted selection. Our study also showed a low differentiation between genotypes selected for disease tolerance and the wild population of ash representing a range of susceptibilities to ash dieback, indicating opportunities for further selection without significantly losing genetic diversity in the ash population.

A Phytoalexin and Aflatoxin Producing Peanut Seed Culture System

1994 ◽  
Vol 21 (2) ◽  
pp. 130-134 ◽  
Author(s):  
S. M. Basha ◽  
R. J. Cole ◽  
S. K. Pancholy
Keyword(s):  
Water Stress ◽  
Culture System ◽  
Fungal Growth ◽  
Aflatoxin Contamination ◽  
Peanut Seed ◽  
Seed Culture ◽  
Murashige And Skoog Medium ◽  
Yellow Orange ◽  
Increased Susceptibility

Abstract An in vitro seed culture system was established to grow peanut seed of different maturities viz. white, yellow, orange, brown and black, using a modified Murashige and Skoog medium. Under this system peanut seed of yellow, orange, brown and black maturity categories grew to maturity as measured by increase in their size and germinability. In vitro cultured seeds produced significant amounts of phytoalexins and were contaminated with aflatoxins following their inoculation with Aspergillus spp. while the noninoculated sterile controls did not produce any phytoalexins. Exposure of seed cultures to water stress using various concentrations of mannitol (0 to 1 M) and polyethylene glycol 8000 (0-30% w/v) caused a significant decrease in their phytoalexin producing ability, and enhanced fungal growth compared to the nonstressed controls. The seeds that were stressed with mannitol and subsequently inoculated with A. flavus and A. parasiticus showed a significant increase in the aflatoxin contamination of stressed seed compared to the unstressed control. This would indicate that in vitro grown seeds responded to water stress similar to the field grown peanuts by loosing their ability to produce phytoalexins and increased susceptibility to aflatoxin contamination. Hence, this system has a potential application in evaluating peanut genotypes for aflatoxin resistance under water stress.

Secondary metabolites from endophytic Streptomyces aureofaciens CMUAc130 and their antifungal activity

Microbiology ◽  
2005 ◽  
Vol 151 (5) ◽  
pp. 1691-1695 ◽  
Author(s):  
Thongchai Taechowisan ◽  
Chunhua Lu ◽  
Yuemao Shen ◽  
Saisamorn Lumyong
Keyword(s):  
Culture Filtrate ◽  
Fungal Growth ◽  
Zingiber Officinale ◽  
Phytopathogenic Fungi ◽  
Active Ingredients ◽  
Streptomyces Aureofaciens ◽  
Mass Spectral ◽  
Causative Agents ◽  
Fungal Growth Inhibition

Streptomyces aureofaciens CMUAc130 was isolated from the root tissue of Zingiber officinale Rosc. (Zingiberaceae). It was an antagonist of Colletotrichum musae and Fusarium oxysporum, the causative agents of anthracnose of banana and wilt of wheat, respectively. Evidence for the in vitro antibiosis of S. aureofaciens CMUAc130 was demonstrated by the zone of fungal-growth inhibition. Microscopic observations showed thickness and bulbous structures at the edges of the inhibited fungal hyphae. The culture filtrate and crude extract from this strain were all inhibitory to tested phytopathogenic fungi. The major active ingredients from the culture filtrate of S. aureofaciens CMUAc130 were purified by silica gel-column chromatography and identified to be (i) 5,7-dimethoxy-4-p-methoxylphenylcoumarin and (ii) 5,7-dimethoxy-4-phenylcoumarin by NMR and mass-spectral data, respectively. Bioassay studies showed that compounds (i) and (ii) had antifungal activities against tested fungi, and their MICs were found to be 120 and 150 μg ml−1, respectively. This is the first report of compounds (i) and (ii) from micro-organisms as active ingredients for the control of phytopathogenic fungi.

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.

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