Unseen, but still present in Czechia: Hymenoscyphus albidus detected by real-time PCR, but not by intensive sampling

Koukol, Ondřej; Haňáčková, Zuzana; Dvořák, Miloň; Havrdová, L.

doi:10.1007/s11557-015-1149-5

Cited by 14 publications

(12 citation statements)

References 27 publications

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“…In empirical studies, disease‐induced extinction tends to be associated with small pre‐epidemic population size and the presence of reservoirs (alternative hosts more abundant than the host of interest) (De Castro & Bolker, ), two factors that are not present for ash dieback. Despite a report of the local disappearance of H. albidus due to competitive exclusion by H. fraxineus (McKinney et al ., ), it could be that H. albidus is surviving the invasion of H. fraxineus (Dvorak et al ., ; Koukol et al ., ). Interestingly, in Korea, H. fraxineus and two closely related cryptic Hymenoscyphus species were found on the same host, showing that co‐occurrence is possible and reproduction barriers are efficient (Gross & Han, ).…”

Section: Discussionmentioning

confidence: 97%

Ash dieback due toHymenoscyphus fraxineus: what can be learnt from evolutionary ecology?

et al. 2016

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The future existence of common ash (Fraxinus excelsior), an important tree species throughout temperate Europe, is threatened. An invasive fungal disease (ash dieback) has spread through much of the distribution area of common ash. The causal agent of the disease is Hymenoscyphus fraxineus, a necrotrophic ascomycete, most probably introduced from Asia in the early 1990s. Hymenoscyphus fraxineus infects ash trees and saplings through their leaves, from which it grows into the stem. The fungus was studied intensively in recent years but there is still a need to address the topic from an evolutionary perspective. In this overview, some key evolutionary aspects of ash dieback are discussed, from the Red Queen dynamics of host–pathogen interactions to the probable consequences for virulence evolution of multiple infections. The progression of ash dieback in Europe does not show spatial differences, but studies show variation in susceptibility within host populations, a probable consequence of genetic differences, thus providing material for evolution of disease resistance or tolerance. Breeding programmes need to maintain the genetic diversity of Fraxinus, to enable it to withstand further threats such as climate change and the emerald ash borer. Because H. fraxineus reproduces exclusively sexually, the pathogen is likely to overcome a narrow genetic resistance. The introduction of further strains of H. fraxineus to Europe and the movement of infected plant material should be avoided. This case study shows that the integration of evolutionary ecology considerations would benefit plant disease management and biosecurity in general.

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Section: Discussionmentioning

confidence: 97%

Ash dieback due toHymenoscyphus fraxineus: what can be learnt from evolutionary ecology?

et al. 2016

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“…In 2010, only H. fraxineus was found. On the other hand, H. albidus was still detected in spore traps in the Czech Republic at low levels, seemingly unaffected by H. fraxineus abundance ( Dvorak et al, 2015 ; Koukol et al, 2016 ). Coexistence of the harmless native species with an invasive sister species has also been observed in the case of Cryphonectria radicalis ( Hoegger et al, 2002 ).…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the ash dieback epidemic may deprive the resident endophytes of their niche and lead to extinctions of host specialized organisms. One example is the native sister species of the ash dieback pathogen, H. albidus , which has become rare or possibly extinct in some severely diseased areas ( McKinney et al, 2012 ; Dvorak et al, 2015 ; Koukol et al, 2016 ).…”

Section: Introductionmentioning

confidence: 99%

The Endophytic Mycobiome of European Ash and Sycamore Maple Leaves – Geographic Patterns, Host Specificity and Influence of Ash Dieback

2018

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The European ash (Fraxinus excelsior) is threatened by the introduced ascomycete Hymenoscyphus fraxineus, the causal agent of ash dieback. Endophytic fungi are known to modulate their host’s resistance against pathogens. To understand possible consequences of ash dieback on the endophytic mycobiome, F. excelsior leaves were collected in naturally regenerated forests and the fungal communities analyzed by classic culture and Illumina amplicon sequencing using a newly developed and validated fungal-specific primer. Collections were done in the area infested by ash dieback north of the Alps, and in the disease free area on the south side. Sycamore maple (Acer pseudoplatanus) was additionally collected, as well as the flowering ash (F. ornus), which occurs naturally in the south and shows tolerance to ash dieback. Both cultivation and amplicon sequencing revealed characteristic endophytic fungal communities dominated by several strictly host specific Venturia species. On A. pseudoplatanus, a hitherto undescribed Venturia species was identified. Due to its dominance on F. excelsior, V. fraxini is unlikely to go extinct in case of reduced host densities. A majority of species was not strictly host specific and is therefore likely less affected by ash dieback in the future. Still, shifts in community structure and loss of genetic diversity cannot be excluded. The potentially endangered endophyte Hymenoscyphus albidus was rarely found. In addition to host specificity, species with preferences for leaf laminae or petioles were found. We also detected considerable geographical variation between sampling sites and clear differences between the two sides of the Alps for endophytes of F. excelsior, but not A. pseudoplatanus. Since sycamore maple is not affected by an epidemic, this could point toward an influence of ash dieback on ash communities, although firm conclusions are not possible because of host preferences and climatic differences. Furthermore, the mycobiota of F. excelsior trees with or without dieback symptoms were compared, but no clear differences were detected. Besides methodical refinement, our study provides comprehensive data on the ash mycobiome that we expect to be subject to changes caused by an emerging disease of the host tree.

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“…The lack of detection of H. albidus spores after 2013 suggests that the fungus was outcompeted by H. fraxineus , which showed an exponential increase in maximum spore level between 2012 and 2015. Studies from Denmark ( Mckinney et al, 2012 ) and UK ( King and Webber, 2016 ) also reported that H. albidus has become rare and probably even locally extinct due, whereas spore trapping studies from the Czech Republic, though based only on one year of sampling, imply that H. albidus could persist even after several years of competition by H. fraxineus ( Dvorak et al, 2016 ; Koukol et al, 2016 ). For H. albidus detection, these Czech studies, like us, employed the primer/probe set designed by Husson et al (2012) .…”

Section: Discussionmentioning

confidence: 99%

Propagule Pressure Build-Up by the Invasive Hymenoscyphus fraxineus Following Its Introduction to an Ash Forest Inhabited by the Native Hymenoscyphus albidus

et al. 2018

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Dieback of European ash, caused by the ascomycete Hymenoscyphus fraxineus originating from Asia, has rapidly spread across Europe, and is threatening this keystone tree at a continental scale. High propagule pressure is characteristic to invasive species. Consistently, the enormous production of windborne ascospores by H. fraxineus in an ash forest with epidemic level of disease obviously facilitates its invasiveness and long distance spread. To understand the rate of build-up of propagule pressure by this pathogen following its local introduction, during 2011–2017 we monitored its sporulation at a newly infested ash stand in south-western Norway characterized with mild winters and cool summers. We also monitored the propagule pressure by Hymenoscyphus albidus, a non-pathogenic native species that competes for the same sporulation niche with H. fraxineus. During the monitoring period, crown condition of ash trees had impaired, and 20% of the dominant trees were severely damaged in 2017. H. fraxineus showed an exponential increase in spore production between 2012 and 2015, followed by drastic decline in 2016 and 2017. During 2011–2013, the two Hymenoscyphus species showed similar sporulation level, but thereafter spores of H. albidus were no longer detected. The data suggest that following local introduction, the population of H. fraxineus reaches rapidly an exponential growth stage if the local weather conditions are favorable for ascomata maturation across years. In the North Atlantic climate, summer temperatures critically influence the pathogen infection pressure, warm summers allowing the population to grow according to its biotic potential, whereas cold summers can cause a drastic decline in propagule pressure.

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Unseen, but still present in Czechia: Hymenoscyphus albidus detected by real-time PCR, but not by intensive sampling

Cited by 14 publications

References 27 publications

Ash dieback due toHymenoscyphus fraxineus: what can be learnt from evolutionary ecology?

Ash dieback due toHymenoscyphus fraxineus: what can be learnt from evolutionary ecology?

The Endophytic Mycobiome of European Ash and Sycamore Maple Leaves – Geographic Patterns, Host Specificity and Influence of Ash Dieback

Propagule Pressure Build-Up by the Invasive Hymenoscyphus fraxineus Following Its Introduction to an Ash Forest Inhabited by the Native Hymenoscyphus albidus

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