Ecology and Disease in Natural Forests

SANIDAD DE LOS BOSQUES DE NOTHOFAGUS. CARACTERIZACIÓN DE SITIO Y ORGANISMOS ASOCIADOS A LA MUERTE AGRUPADA

Thesis

Full-text available

Jun 2022

Lucía Molina

Temperate forests have been threatened, in recent decades, by events of death and decay throughout the globe. The causes have been investigated without, in many cases, revealing a primary cause of the deterioration. This gave rise to a concept that is increasingly used to evaluate these phenomena, which is that of complex diseases. In this context, the endophytic mycobiome of trees plays an important role as a recent object of study and integration in interpretations of forest health. In recent decades, a phenomenon of grouped death of unknown etiology has been observed in the two Nothofagus species with the widest distribution in the forests of North Patagonia: N. dombeyi and N. pumilio. Within the framework of this thesis, the phenomenon of the grouped death of Nothofagus in Los Alerces National Park (Chubut) was described, characterizing for the first time in the field the symptoms, signs, damage and characteristics of the site and the stand. The endophytic mycobiota of stem and root wood of Nothofagus was analyzed in stands with clustered death and beta diversity was described along environmental and host variables as a contribution to its autoecology and in search of possible associations between the mycobiota and the phenomenon of grouped death. The study of these communities was developed through two methodological approaches: one by isolation prospecting and another by massive sequencing of the ITS1 molecular marker from environmental DNA using the MiSeq Illumina platform. The diversity results obtained by both approaches were analyzed, but the performance of the new technologies was also evaluated using the database of sequences obtained by crop prospecting as a comparison criterion. The application of second-generation sequencing technologies for the study of endophytic fungal communities in wood proved to be complementary to culture-dependent approaches and allowed deepening of beta diversity patterns, detecting greater heterogeneity than with culture. Although more pathogenic organisms were recovered from symptomatic than asymptomatic N. dombeyi in the culture study, the independent approach allowed us to detect that both species of Nothofagus carry a wide diversity of potential fungal pathogens in their sapwood, both in trees that present visible symptoms and those of healthy appearance. The grouped death of Nothofagus is revealed as a complex phenomenon in which many biotic and abiotic variables are interacting and in which, in this framework, the wood endophytic mycobiota would be playing a secondary role. Both species of Nothofagus carry different fungal assemblages, with very little overlap, but both very diverse. In N. dombeyi, the site turned out to be the most important factor in the differentiation of the assemblages. The variations observed were related with site-features such as climate, topography and water availability, reflecting the greater heterogeneity of sites in which this species is distributed. Nothofaugs pumilio showed a strong susceptibility to seasonality and greater compartmentalization between root and stem, which translates into an increase in rotting and degrading fungal organisms with warm and drier periods. Similarly, during cold periods, the root acts as a reservoir of diversity of fungal organisms with other trophic strategies. This is definitely something that we are interested in continuing to investigate, given the general context of climate change that temperate forests are facing around the globe.

SANIDAD DE LOS BOSQUES DE NOTHOFAGUS. CARACTERIZACIÓN DE SITIO Y ORGANISMOS ASOCIADOS A LA MUERTE AGRUPADA

Preprint

Full-text available

Jun 2022

Lucía Molina

Temperate forests have been threatened, in recent decades, by events of death and decay throughout the globe. The causes have been investigated without, in many cases, revealing a primary cause of the deterioration. This gave rise to a concept that is increasingly used to evaluate these phenomena, which is that of complex diseases. In this context, the endophytic mycobiome of trees plays an important role as a recent object of study and integration in interpretations of forest health. In recent decades, a phenomenon of grouped death of unknown etiology has been observed in the two Nothofagus species with the widest distribution in the forests of North Patagonia: N. dombeyi and N. pumilio. Within the framework of this thesis, the phenomenon of the grouped death of Nothofagus in Los Alerces National Park (Chubut) was described, characterizing for the first time in the field the symptoms, signs, damage and characteristics of the site and the stand. The endophytic mycobiota of stem and root wood of Nothofagus was analyzed in stands with clustered death and beta diversity was described along environmental and host variables as a contribution to its autoecology and in search of possible associations between the mycobiota and the phenomenon of grouped death. The study of these communities was developed through two methodological approaches: one by isolation prospecting and another by massive sequencing of the ITS1 molecular marker from environmental DNA using the MiSeq Illumina platform. The diversity results obtained by both approaches were analyzed, but the performance of the new technologies was also evaluated using the database of sequences obtained by crop prospecting as a comparison criterion. The application of second-generation sequencing technologies for the study of endophytic fungal communities in wood proved to be complementary to culture-dependent approaches and allowed deepening of beta diversity patterns, detecting greater heterogeneity than with culture. Although more pathogenic organisms were recovered from symptomatic than asymptomatic N. dombeyi in the culture study, the independent approach allowed us to detect that both species of Nothofagus carry a wide diversity of potential fungal pathogens in their sapwood, both in trees that present visible symptoms and those of healthy appearance. The grouped death of Nothofagus is revealed as a complex phenomenon in which many biotic and abiotic variables are interacting and in which, in this framework, the wood endophytic mycobiota would be playing a secondary role. Both species of Nothofagus carry different fungal assemblages, with very little overlap, but both very diverse. In N. dombeyi, the site turned out to be the most important factor in the differentiation of the assemblages. The variations observed were related with site-features such as climate, topography and water availability, reflecting the greater heterogeneity of sites in which this species is distributed. Nothofaugs pumilio showed a strong susceptibility to seasonality and greater compartmentalization between root and stem, which translates into an increase in rotting and degrading fungal organisms with warm and drier periods. Similarly, during cold periods, the root acts as a reservoir of diversity of fungal organisms with other trophic strategies. This is definitely something that we are interested in continuing to investigate, given the general context of climate change that temperate forests are facing around the globe.

Armillaria luteobubalina in regrowth karri stands in Western Australia

Conference Paper

Full-text available

Nov 2007

Richard Robinson

Armillaria luteobubalina is an endemic pathogen of dry sclerophyll forests and woodlands of southern Australia. The fungus infects the roots of susceptible hosts causing a root and butt rot, commonly referred to as Armillaria root disease (ARD). In high quality regrowth karri stands, ARD causes significant losses due to mortality and defect, which are exacerbated by intensive management practices such as thinning. This review gives a brief outline of what is known about Armillaria luteobubalina and Armillaria root disease in karri regrowth forests of Western Australia and discusses options available for disease control.

Distribution, ecology and host range of Armillaria species in Albania

Article

Full-text available

Oct 2009

Summary Species of Armillaria were identified from 645 isolates obtained in a nation-wide survey in Albania. The material was collected from ca. 250 permanent plots, established for monitoring forest health, and from forests and orchards attacked by Armillaria. Armillaria mellea s.s. occurred on several coniferous and broadleaved trees in most areas examined, although it was absent above 1100-1200 m in northern Albania. This species damaged Abies and Quercus spp. and, to a lesser extent, other forest trees. A. mellea was also commonly recorded causing damage in orchards and vineyards. Armillaria gallica was a common saprophyte or weak pathogen in coniferous and deciduous forests at altitudes from 600 to 1600 m, and less commonly on oaks at lower altitudes. Armillaria ostoyae was rare in central and southern Albania, but common in northern Albania, causing significant damage to pine and other conifers, mostly at altitudes from 600 to 1800 m. Armillaria cepistipes was recorded at altitudes from 800 to 1800 m as a saprophyte or weak pathogen on conifers and deciduous trees, mostly in beech and silver fir forests. Armillaria tabescens was found in oak forests at altitudes from sea level to 900 m. In orchards, A. tabescens occasionally attacked almond and pear trees. Armillaria borealis was found in a few locations in northern Albania, at altitudes from 800 to 1800 m.

Distribution, ecology and host range of Armillaria species in Albania

Article

Full-text available

Oct 2010

Species of Armillaria were identified from 645 isolates obtained in a nation-wide survey in Albania. The material was collected from ca. 250 permanent plots, established for monitoring forest health, and from forests and orchards attacked by Armillaria. Armillaria mellea s.s. occurred on several coniferous and broadleaved trees in most areas examined, although it was absent above 1100–1200 m in northern Albania. This species damaged Abies and Quercus spp. and, to a lesser extent, other forest trees. Armillaria mellea was also commonly recorded causing damage in orchards and vineyards. Armillaria gallica was a common saprophyte or weak pathogen in coniferous and deciduous forests at altitudes from 600 to 1600 m, and less commonly on oaks at lower altitudes. Armillaria ostoyae was rare in central and southern Albania, but common in northern Albania, causing significant damage to pine and other conifers, mostly at altitudes from 600 to 1800 m. Armillaria cepistipes was recorded at altitudes, from 800 to 1800 m as a saprophyte or weak pathogen on conifers and deciduous trees, mostly in beech and silver fir forests. Armillaria tabescens was found in oak forests at altitudes from sea level to 900 m. In orchards, A. tabescens occasionally attacked almond and pear trees. Armillaria borealis was found in a few locations in northern Albania, at altitudes from 800 to 1800 m.

Lusaj et al. FP

Data

Full-text available

Apr 2016

Distribution, ecology and host range of Armillaria species in Albania

Article

Full-text available

Sep 2009

Species of Armillaria were identified from 645 isolates obtained in a nation-wide survey in Albania. The material was collected from ca. 250 permanent plots, established for monitoring forest health, and from forests and orchards attacked by Armillaria. Armillaria mellea s.s. occurred on several coniferous and broadleaved trees in most areas examined, although it was absent above 1100-1200 m in northern Albania. This species damaged Abies and Quercus spp. and, to a lesser extent, other forest trees. A. mellea was also commonly recorded causing damage in orchards and vineyards. Armillaria gallica was a common saprophyte or weak pathogen in coniferous and deciduous forests at altitudes from 600 to 1600 m, and less commonly on oaks at lower altitudes. Armillaria ostoyae was rare in central and southern Albania, but common in northern Albania, causing significant damage to pine and other conifers, mostly at altitudes from 600 to 1800 m. Armillaria cepistipes was recorded at altitudes from 800 to 1800 m as a saprophyte or weak pathogen on conifers and deciduous trees, mostly in beech and silver fir forests.Armillaria tabescens was found in oak forests at altitudes from sea level to 900 m. In orchards, A. tabescens occasionally attacked almond and pear trees. Armillaria borealis was found in a few locations in northern Albania, at altitudes from 800 to 1800 m.

Survey for Armillaria by Plant Associations in Northern Arizona

Article

Full-text available

Sep 2014
J Arizona Nevada Acad Sci

Fungi in the genus Armillaria are associated with an important disease of deciduous and coniferous trees and shrubs in western North America. This study examined the distribution of Armillaria by forest habitat types on the Kaibab National Forest and northern Coconino National Forest, Arizona. Over 400 trees were examined for Armillaria in 76 Interior West Forest Inventory and Analysis permanent plots representing 17 different habitat types. Samples of the fungus associated with Armillaria root disease were collected from 23 trees and identified using DNA sequencing. All samples were determined to consist of a single species, Armillaria solidipes Peck [= A. ostoyae (Romagnesi) Herink]. Only 10 of the 76 plots and 5 of the 17 habitat types sampled had Armillaria solidipes present on one or more trees. A. solidipes was more commonly found in mixed-conifer and subalpine forests and was rare in ponderosa pine (Pinus ponderosa Doug. Ex. Larson & C. Larson) forests, which was consistent with previous root disease studies conducted in the Southwest. However, our estimates of Armillaria presence may be conservative since we did not examine entire root systems.

Mapping pathogenic fungi in decayed Norway spruce stands: Insights from harvester positional data

Article

Full-text available

Oct 2024
J APPL ECOL

Root and butt rot caused by pathogenic fungi in the genera Heterobasidion and Armillaria is a pressing issue in managed Norway spruce forests. The disease results in financial losses for the forest owners and reduces the volume of wood that can be used in long‐lived products. Pathogenic wood decay fungi spread either with the aid of airborne spores or via mycelial growth among neighbouring trees, the latter leading to clustering (tendency of decayed trees to be in close proximity relative to their neighbouring trees) of decay‐affected trees in forests. Understanding the spatial patterns of the decay‐affected trees at the forest stand level is vital for designing management strategies to address this problem. We examined decay clustering in 273 clear‐cut Norway spruce stands in Norway using harvester‐recorded data on spatial occurrence of decayed and healthy Norway spruce trees. We tested clustering using three global‐cluster tests that account for population density and distribution, evaluating clustering without identifying specific cluster locations. The proportions of clustered and non‐clustered stands differed depending on the statistical test used for clustering assessment, resulting in overall agreement of 32.8% for clustered and 36.9% for non‐clustered. Clustered stands exhibited a median cluster distance (maximum distance between the decay‐affected trees within a cluster) of 12 m (Inter‐Quantile Range, IQR, 6–20 m) and a median of 6 (IQR 3–16) nearest neighbour trees (number of decayed trees forming a cluster), estimates comparable with prior studies focused on assessment of trees infected by mycelial spread of the same fungal individual. The decay incidence in the clustered stands was 16.24%, while the non‐clustered stands had a butt‐rot incidence of 20.97%. In clustered stands the average number of trees per hectare was higher (693) than in non‐clustered stands (553). Synthesis and applications: Our study demonstrates that Norway spruce stands display a diverse range of spatial patterns of butt rotted trees. We found that higher densities of Norway spruce trees probably facilitate the vegetative spread of pathogenic wood decay fungi, leading to clustering of decay‐affected trees. To disrupt the spread of decay fungi between tree generations, precision planting of trees other than Norway spruce around infested stumps of prior generation trees has been recommended by earlier studies. We discussed the potential of using harvester‐derived geoposition data for butt‐rotted trees upon planning and execution of forest regeneration.

Weather Conditions Drive the Damage Area Caused by Armillaria Root Disease in Coniferous Forests across Poland

Article

Full-text available

Dec 2023
PLANT PATHOLOGY J

Armillaria root disease affects forests around the world. It occurs in many habitats and causes losses in the infested stands. Weather conditions are important factors for growth and development of Armillaria species. Yet, the relation between occurrence of damage caused by Armillaria disease and weather variables are still poorly understood. Thus, we used generalized linear mixed models to determine the relationship between weather conditions of current and previous year (temperature, precipitation and their deviation from long-term averages , air humidity and soil temperature) and the incidence of Armillaria-induced damage in young (up to 20 years old) and older (over 20 years old) coniferous stands in selected forest districts across Poland. We used unique data, gathered over the course of 23 years (1987-2009) on tree damage incidence from Armillaria root disease and meteorological parameters from the 24-year period (1986-2009) to reflect the dynamics of damage occurrence and weather conditions. Weather parameters were better predictors of damage caused by Armillaria disease in younger stands than in older ones. The strongest predictor was soil temperature, especially that of the previous year growing season and the current year spring. We found that temperature and precipitation of different seasons in previous year had more pronounced effect on the young stand area affected by Armillaria. Each stand's age class was characterized by a different set of meteorological parameters that explained the area of disease occurrence. Moreover, forest district was included in all models and thus, was an important variable in explaining the stand area affected by Armillaria.

Sapwood-inhabiting mycobiota and Nothofagus tree mortality in Patagonia: Diversity patterns according to tree species, plant compartment and health condition

Article

Apr 2020
FOREST ECOL MANAG

Temperate forests ecosystems are threatened by declines and diseases worldwide. Causes have been investigated during the last decades allowing, in some cases, to relate such deterioration to climate change or pathogens but, in many cases, causes have not yet been elucidated. In recent decades, a phenomenon of grouped mortality, whose etiology remains unknown, has been observed in the two most distributed Nothofagus species of North Patagonian forests. This study aimed to assess sapwood-inhabiting fungal diversity of N. dombeyi and N. pumilio trees in healthy and affected stands in order to determine whether health condition shape these fungal communities, to characterize such patterns and, to seek for the likely pathogens associated with tree damage. Seven sites in Los Alerces National Park (Chubut, Argentina), were sampled seasonally for two years. Eighty-eight fungal taxa were recovered and identified. Spatial heterogeneity across plant compartments was found, involving community composition and structure, with stem harbouring greater diversity than root. It was found that the sapwood in both Nothofagus species was inhabited by different fungal species, in high richness and showing different patterns according to health condition and plant compartment. Health condition was a stronger driver of N. dombeyi sapwood-inhabiting fungal community than it was for N. pumilio; the latter evidenced plant compartment as a stronger driver of such community. Nothofagus pumilio presented higher frequency of decomposition agents in both affected and healthy trees than it was in N. dombeyi, indicating a greater wood deterioration of its stands. More decomposition agents and potential pathogens have been found in symptomatic stands of N. dombeyi than in healthy stands, although their frequency patterns do not allow the inference of conclusions about the primary fungal agent causing tree mortality. Our findings suggest a secondary role of living-wood-inhabiting mycobiota in tree damage processes as an expression of tree stress caused by climatic factors.

Potential Interactions between Invasive Fusarium circinatum and Other Pine Pathogens in Europe

Article

Full-text available

Dec 2019

Pines are major components of native forests and plantations in Europe, where they have both economic significance and an important ecological role. Diseases of pines are mainly caused by fungal and oomycete pathogens, and can significantly reduce the survival, vigor, and yield of both individual trees and entire stands or plantations. Pine pitch canker (PPC), caused by Fusarium circinatum (Nirenberg and O’Donnell), is among the most devastating pine diseases in the world, and is an example of an emergent invasive disease in Europe. The effects of microbial interactions on plant health, as well as the possible roles plant microbiomes may have in disease expression, have been the focus of several recent studies. Here, we describe the possible effects of co-infection with pathogenic fungi and oomycetes with F. circinatum on the health of pine seedlings and mature plants, in an attempt to expand our understanding of the role that biotic interactions may play in the future of PPC disease in European nurseries and forests. The available information on pine pathogens that are able to co-occur with F. circinatum in Europe is here reviewed and interpreted to theoretically predict the effects of such co-occurrences on pine survival, growth, and yield. Beside the awareness that F. circinatum may co-occurr on pines with other pathogens, an additional outcome from this review is an updating of the literature, including the so-called grey literature, to document the geographical distribution of the relevant pathogens and to facilitate differential diagnoses, particularly in nurseries, where some of them may cause symptoms similar to those induced by F. circinatum. An early and accurate diagnosis of F. circinatum, a pathogen that has been recently introduced and that is currently regulated in Europe, is essential to prevent its introduction and spread in plantings and forests.

Effects of Climate Change on Ecological Disturbance in the Northern Rockies

Chapter

Full-text available

Jul 2018

Disturbances alter ecosystem, community, or population structures and change elements of the biological and/or physical environment. Climate changes can alter the timing, magnitude, frequency, and duration of disturbance events, as well as the interactions of disturbances on a landscape, and climate change may already be affecting disturbance events and regimes. Interactions among disturbance regimes, such as the co-occurrence in space and time of bark beetle outbreaks and wildfires, can result in highly visible, rapidly occurring, and persistent changes in landscape composition and structure. Understanding how altered disturbance patterns and multiple disturbance interactions might result in novel and emergent landscape behaviors is critical for addressing climate change impacts and for designing land management strategies that are appropriate for future climates. This chapter describes the ecology of important disturbance regimes in the Northern Rockies region, and potential shifts in these regimes as a consequence of observed and projected climate change. We summarize five disturbance types present in the Northern Rockies that are sensitive to a changing climate—wildfires, bark beetles, white pine blister rust (Cronartium ribicola), other forest diseases, and nonnative plant invasions—and provide information that can help managers anticipate how, when, where, and why climate changes may alter the characteristics of disturbance regimes.

Hongos agaricoides de los bosques de Nothofagus pumilio (Chubut, Argentina): Clave y listado de especies

Article

Full-text available

Jun 2017

Se han realizado abundantes expediciones micológicas en Patagonia, pero los sitios relevados han cubierto solo una porción minima de esta extensa región. Así, las expediciones micológicas se centraron en los extremos norte (Neuquén y Rio Negro en Argentina, Santiago y Maule en Chile) y sur (Tierra del Fuego argentina y chilena) de los bosques subantárticos. El territorio comprendido entre estas provincias permanence inexplorado para los hongos agaricoides. El objetivo central de este trabajo fue evaluar la riqueza de especies de hongos agaricoides en bosques puros de Nothofagus pumilio (lenga) en Chubut (Argentina). Se realizaron 4 viajes de muestreo entre 2012 y 2014 en 3 bosques en la provincia del Chubut, Argentina. Se encontraron 130 especies de hongos agaricoides. Entre ellas, 125 pertenecen al orden Agaricales, 2 al orden Boletales y 3 al orden Russulales. La familia Cortinariaceae (Agaricales) fue la más rica, con 57 especies. Se presenta una clave para todas las especies halladas. Fueron encontrados 4 nuevos registros a nivel nacional y 124 a nivel provincial.

Resolved phylogeny and biogeography of the root pathogen Armillaria and its gasteroid relative, Guyanagaster

Article

Full-text available

Jan 2017
BMC EVOL BIOL

Background Armillaria is a globally distributed mushroom-forming genus composed primarily of plant pathogens. Species in this genus are prolific producers of rhizomorphs, or vegetative structures, which, when found, are often associated with infection. Because of their importance as plant pathogens, understanding the evolutionary origins of this genus and how it gained a worldwide distribution is of interest. The first gasteroid fungus with close affinities to Armillaria—Guyanagaster necrorhizus—was described from the Neotropical rainforests of Guyana. In this study, we conducted phylogenetic analyses to fully resolve the relationship of G. necrorhizus with Armillaria. Data sets containing Guyanagaster from two collecting localities, along with a global sampling of 21 Armillaria species—including newly collected specimens from Guyana and Africa—at six loci (28S, EF1α, RPB2, TUB, actin-1 and gpd) were used. Three loci—28S, EF1α and RPB2—were analyzed in a partitioned nucleotide data set to infer divergence dates and ancestral range estimations for well-supported, monophyletic lineages. Results The six-locus phylogenetic analysis resolves Guyanagaster as the earliest diverging lineage in the armillarioid clade. The next lineage to diverge is that composed of species in Armillaria subgenus Desarmillaria. This subgenus is elevated to genus level to accommodate the exannulate mushroom-forming armillarioid species. The final lineage to diverge is that composed of annulate mushroom-forming armillarioid species, in what is now Armillaria sensu stricto. The molecular clock analysis and ancestral range estimation suggest the most recent common ancestor to the armillarioid lineage arose 51 million years ago in Eurasia. A new species, Guyanagaster lucianii sp. nov. from Guyana, is described. Conclusions The armillarioid lineage evolved in Eurasia during the height of tropical rainforest expansion about 51 million years ago, a time marked by a warm and wet global climate. Species of Guyanagaster and Desarmillaria represent extant taxa of these early diverging lineages. Desarmillaria represents an armillarioid lineage that was likely much more widespread in the past. Guyanagaster likely evolved from a gilled mushroom ancestor and could represent a highly specialized endemic in the Guiana Shield. Armillaria species represent those that evolved after the shift in climate from warm and tropical to cool and arid during the late Eocene. No species in either Desarmillaria or Guyanagaster are known to produce melanized rhizomorphs in nature, whereas almost all Armillaria species are known to produce them. The production of rhizomorphs is an adaptation to harsh environments, and could be a driver of diversification in Armillaria by conferring a competitive advantage to the species that produce them. Electronic supplementary material The online version of this article (doi:10.1186/s12862-017-0877-3) contains supplementary material, which is available to authorized users.

The Parenchyma of Secondary Xylem and Its Critical Role in Tree Defense against Fungal Decay in Relation to the CODIT Model

Article

Full-text available

Nov 2016

This review examines the roles that ray and axial parenchyma (RAP) plays against fungal pathogens in the secondary xylem of wood within the context of the CODIT model (Compartmentalization of Decay in Trees), a defense concept first conceived in the early 1970s by Alex Shigo. This model, simplistic in its design, shows how a large woody perennial is highly compartmented. Anatomical divisions in place at the time of infection or damage, (physical defense) alongside the ‘active’ response by the RAP during and after wounding work together in forming boundaries that function to restrict air or decay spread. The living parenchyma cells play a critical role in all of the four walls (differing anatomical constructs) that the model comprises. To understand how living cells in each of the walls of CODIT cooperate, we must have a clear vision of their complex interconnectivity from a three-dimensional perspective, along with knowledge of the huge variation in ray parenchyma (RP) and axial parenchyma (AP) abundance and patterns. Crucial patterns for defense encompass the symplastic continuum between both RP and AP and the dead tissues, with the latter including the vessel elements, libriform fibers, and imperforate tracheary elements (i.e., vasicentric and vascular tracheids). Also, the heartwood, a chemically altered antimicrobial non-living substance that forms the core of many trees, provides an integral part of the defense system. In the heartwood, dead RAP can play an important role in defense, depending on the genetic constitution of the species. Considering the array of functions that RAP are associated with, from capacitance, through to storage, and long-distance water transport, deciding how their role in defense fits into this suite of functions is a challenge for plant scientists, and likely depends on a range of factors. Here, we explore the important role of RAP in defense against fungal pathogens and the trade-offs involved from a viewpoint for structure-function relations, while also examining how fungi can breach the defense system using an array of enzymes in conjunction with the physically intrusive hyphae.

Observed and anticipated impacts of drought on forest insects and diseases in the United States

Article

May 2016
FOREST ECOL MANAG

THE OCCURRENCE OF ARMILLARIA SPECIES IN SIEMIANICE EXPERIME NTAL FOREST DISTRICT

Article

Full-text available

Jan 2011

The objective of the presented st udies was the determination of Armillaria spe- cies causing root rot in stands growing in habi tats of a higher fertility in the Siemianice Experimental Forest District. With the application of the mycelium intersterility test, the occurrence of A. gallica and A. ostoyae was found on the area of the mentioned Forest District, while in the nearby situated Mansion Park, Armillaria cepistipes was identified

Mycelial fan formation of three sympatric Armillaria species on excised stem segments of Picea abies

Article

Nov 2015
FOREST PATHOL

Mycelial fan formation was studied in five Armillaria cepistipes, ten A. borealis and ten diploid and six haploid A. ostoyae strains on excised stem segments of Picea abies. Stem segments were either non-autoclaved or autoclaved, representing dying and dead wood, respectively. To confirm the identity of mycelial fans on non-autoclaved stem segments, re-isolations were made and isolates characterized with microsatellite markers. Mycelial fan formation on autoclaved stem segments was fast and reliable for most of the tested Armillaria strains. On non-autoclaved stem segments, mycelial fan formation was slower, more erratic and less predictable. Mycelial fan formation was fastest in A. cepistipes closely followed by A. borealis and was slowest in A. ostoyae. For two A. cepistipes and four A. ostoyae strains (all diploid), growth rates of mycelial fans were estimated in a time course experiment. They ranged between 5.1 and 8.7 mm/day for autoclaved and between 1.4 and 4.7 mm/day for non-autoclaved stem segments. The haploid A. ostoyae strains also formed mycelial fans on autoclaved stem segments, but typically slower and less reliably than the diploid strains. Whether haploid strains are able to produce mycelial fans on non-autoclaved stem segments remains unknown because of accidental diploidization of the original haploid strains which was likely caused by basidiospores introduced into the study system on the non-autoclaved stems. Overall, the method developed in this study may be useful for further investigations into the genetic, physiological and biochemical nature of mycelial fan formation in the genus Armillaria.

Climate change and forest diseases: Using today's knowledge to address future challenges

Article

Jul 2012

Rona N. Sturrock

The health of the earth's forests and urban green spaces is increasingly challenged by the outcomes of human activities, including global climate change. As climate changes, the role and impact of diseases on trees in both forest ecosystems and in urban settings will also change. Knowledge of relationships between climate variables and diseases affecting forest and urban trees is reviewed, with specific emphasis on those affecting foliage, shoots, and stems. Evidence that forest diseases are already responding to the earth's changing climate is examined (e.g., Dothistroma needle blight in northern British Columbia) as are predicted scenarios for future changes in impact on forests by other tree diseases. Outbreaks of tree diseases caused by native and alien pathogens are predicted to become more frequent and intense - this and other general predictions about the effects of climate change on forest and tree diseases are discussed. Despite the uncertainty that accompanies such predictions it is imperative that researchers, forest and urban tree managers, and policy makers work together to develop and implement management strategies that enhance the resilience of the worlds' forests and urbanized trees. Strategies discussed include monitoring, forecasting, planning, and mitigation.

Phylogenetic relationships among biological species of Armillaria from China

Article

Jun 2015
Mycoscience

Fourteen Chinese Biological Species (CBS) of Armillaria were previously identified in a collection of Chinese isolates. CBS C, F, G, H, J, L, N and O remained unnamed, while the remaining isolates included A. borealis, A. cepistipes, A. gallica, A. mellea, A. sinapina and A. tabescens. CBS F was suggested to represent A. singula based on basidiocarp morphology. In this study, phylogenetic relationships between Chinese Armillaria isolates and those from other parts of the world were determined based on DNA sequence data. Results of this study suggest that CBS F might not represent A. singula, and that A. monadelpha (a name applied to the North American form of A. tabescens by some authors) and A. tabescens should be treated as a single species. Four main phylogenetic lineages, referred to as the A. ostoyae, A. gallica, A. tabescens and A. mellea clusters, were identified on the phylogenetic trees. The unnamed biological species grouped within the “A. gallica cluster” and were phylogenetically closely related. The results of this study contribute to our current understanding of the systematics of Armillaria from South East Asia where these fungi are relatively poorly known.

NEW LOCATION OF ARMILLARIA MELLEA IN POLISH FORESTS

Article

Piotr Łakomy

Armillaria root rot is the most important disease of woody plants in forest, hor-ticulture plantations, and in house gardens all over the world. Armillaria spp. can infect more than 600 species of trees, shrubs and herbaceous plants (Hood et al. 1991, Kile et al. 1991, Mańka 2005). The Armillaria genus includes more than 40 species. In Europe seven species were noted and in Poland six (Domański et al. 1967, Pegler 2000, Żółciak 2005). In Polish forests Armillaria ostoyae is the most common species occurring in al-most all forest sites. Armillaria borealis and A. cepistipes have been noted on conifer-ous and deciduous trees or shrubs. Armillaria gallica is most common species in oak stands and plays an important role in the complex of factors causing oak decline in many oak stands. Armillaria mellea was found only in one forest ecosystem (oak stand, Zielonka Forest District; Łakomy 2001) and in three other places – vineyard and two small groups of poplars out of forest (Żółciak 1999 a, b). The sixth species – A. tabescens was described in 1967 (Domański et al. 1967) from beech stumps in two forest districts in south-eastern Poland (Bieszczady Mountains, Stuposiany and Wetlina Forest Districts). Four Armillaria species (excluding A. tabescens and A. mellea) were noted by many authors (Rykowski 1990, Żółciak 1991, Mańka and Łakomy 1995, Kowalski et al. 1997, Łakomy 1998, Żółciak 1999 a, b, Łakomy and Siwecki 2000, Szewczyk and Mańka 2002, Łakomy 2004). In 2006 two groups of A. mellea basidiomes were found in two localities in Strzelce Krajeńskie Forest District (compartment 177c and on the border between compartments 177c and 177f). One group was growing in the middle of a forest path (2 m from an oak stump), which was the border between a mixed stand (Larix decidua, Pinus sylvestris 55-year-old, Quercus petraea, Fagus sylvatica, Carpinus betulus 62-year-old, 177f) and a 64-year-old Scots pine stand with single birch (Betula pendula) and oak trees (177c, Phot. 1). In the second locality basidiomes appeared close to a birch stump in a Scots pine stand (177c, Phot. 2). These two localities were less than 100 m distant from each other. In the pine stand basidiomes were found close to a neighbouring oak stand (about 50 m). The two groups of basidiomes differed from each other. Pilei of basidiomes from the path were bigger than those found on stump, and open. The margin of basidiomes growing close to the stump was rolled down.

MOLECULAR CHARACTERIZATION OF SOUTHEASTERN ARMILLARIA ISOLATES

Article

Karol Leigh Kelly

The genus Armillaria contains white-rot basidiomycetes pathogenic to woody plant hosts worldwide. Of particular interest are the species found in southeastern peach (Prunus persica) orchards causing Armillaria root rot. Isolates collected during the past four years from orchards in Georgia, South Carolina, and Alabama were identified to species and grouped within species based on molecular analysis of the internal transcribed spacer (ITS) regions and the intergenic spacer (IGS) regions of the ribosomal DNA (rDNA). Thirty isolates of A. tabescens and nine isolates of A. mellea were identified from these orchards. Restriction fragment length polymorphism (RFLP) analysis of the IGS region with Alu I revealed two groups of A. tabescens and one group of A. mellea. Similarly, the ITS region was amplified with primer sets At-ITS1/Am-ITS1/ITS-2 and ITS-1/ITS-4 and subsequently restricted with Mbo II and Hha I. These restrictions indicated two groups of A. tabescens and four groups of A. mellea.

Development and verification of a diagnostic assay based on EF‐1 α for the identification of Armillaria species in Northern Europe

Article

Jun 2012

The overall aim of this study was to develop a new, reliable and rapid diagnostic assay for differentiating six European Armillaria species based on variation in their elongation factor‐1 alpha (EF‐1 α) gene sequences and to verify a set of species‐specific primers on 61 Armillaria isolates from Europe. Partial sequences of the EF‐1 α gene obtained in Armillaria borealis, Armillaria cepistipes, Armillaria gallica, Armillaria mellea, Armillaria ostoyae and Armillaria tabescens revealed sufficient interspecific variation to distinguish among species using nested primers. These primers gave unambiguous bands when tested on representative isolates of five of these species. However, the EF‐1 α sequences of European A. borealis isolates clustered into two distinct clades, termed here AbX and AbY. Specific primers were subsequently designed and tested successfully on both AbX‐type and AbY‐type A. borealis isolates. The taxonomy of A. borealis needs to be elucidated to determine whether a new, as yet unnamed Armillaria taxon exists in Europe. Three A. borealis isolates were also found to have heterozygous sites in their EF‐1 α sequences, which suggests that the gene could exist in more than one copy or that these isolates contain hybrid sequences. A pyrosequencing method was also developed, targeting a small region of EF‐1 α intron 4, which was able to differentiate European Armillaria isolates to the species level and additionally could distinguish AbX‐type and AbY‐type A. borealis isolates.

Short-term impact of thinning and fertilizer application on Armillaria root disease in regrowth karri (Eucalyptus diversicolor F. Muell.) in Western Australia

Article

Mar 2003
FOREST ECOL MANAG

Richard Robinson

The incidence of Armillaria root disease was recorded during routine measurement of a silvicultural experiment designed to test the effect of thinning and nitrogen fertilizer application on the growth of karri regenerated after clearfelling. The experiment was established in 1984, when the stand was 12-year-old. Ten years after thinning, the level of disease increased significantly with increased thinning intensity, and disease accounted for 51% of the mortality in the plots thinned to 200 stems/ha. Fifteen years after thinning, the level of infection had increased in all treatments but was still significantly lower in the unthinned treatment. In the thinned treatments, 54–63% of the trees ranked in the largest 200 stems/ha were infected, and 50–100% of the mortality within these trees was attributed to Armillaria luteobubalina. In the unthinned treatment, no mortality within the dominant trees was associated with disease. Ten years after thinning and fertilizer treatments, it could not be determined whether fertilizer application had had any effect on the level of disease. Whole tree thinning, which results in stump and root removal, is discussed as a viable management option in high-quality karri regrowth stands infested with A. luteobubalina.

Ecological Factors Influencing the Occurrence of Armillaria mellea (Basidiomycota, Agaricales, Physalacriaceae) in Yuvacik Dam Watershed in Kocaeli, Türkiye

Article

Full-text available

Jun 2023

The occurrence of Armillaria mellea (Vahl) P. Kumm. and the ecological characteristics of this fungus were studied in Kocaeli, Yuvacik dam basin mixed-broad leaved forests. During the surveys, we analyzed the sporocarps (fruiting bodies) of A. mellea growing up on woody plants in plots selected by cluster sampling in the Yuvacik dam watershed dominated by broad-leaved forests. The Runs test results showed that randomness rules complied in the selection of the plots, and there was no tendency (p= 0.109 > 0.05, z= -1.603). The presence/absence of A. mellea and environmental variables were tested with Chi-square analysis, and the temperature differed among these environmental variables. To the dendrogram, A. mellea was mainly seen in the south of the study area and preferred western aspects. It is understood that this macrofungus prefers the south of the study area because of the altitude. Our data showed that sporocarps of A. mellea generally occurred in the western aspect, at temperatures of 15–20°C, >80% humidity and 800–1000 m altitude. Our logistic regression analysis model (z=-9.508+0.307×temperature+0.081×humidity) showed that if the temperature and humidity change by 1 unit in the region, sporocarp formation is affected by 36% and 8.4%, respectively.

Armillaria novae-zelandiae

Article

Jan 2022

Ian Hood

This datasheet on Armillaria novae-zelandiae covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Diagnosis, Biology & Ecology, Environmental Requirements, Impacts, Uses, Prevention/Control, Further Information.

Armillaria limonea

Article

Jan 2022

This datasheet on Armillaria limonea covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Diagnosis, Biology & Ecology, Environmental Requirements, Impacts, Uses, Prevention/Control, Further Information.

El patógeno forestal Armillaria como fuente de enzimas ligninolíticas con potencial biotecnológico

Thesis

Full-text available

Mar 2016

Lucía Molina

Armillaria es un género de hongos de la pudrición blanca y constituye uno de los patógenos más ampliamente estudiados por las pérdidas que ocasiona en la actividad forestal. En los últimos años se ha comenzado a utilizar la batería enzimática ligninolítica de este organismo en actividades de biorremediación que involucran la producción de enzimas extracelulares y la transformación de colorantes. En Argentina este patógeno está asociado a bosque nativo e implantado de Patagonia y recientemente han sido dilucidadas su taxonomía y filogenia estableciéndose cuatro linajes correspondientes a cuatro especies. El objetivo de este trabajo fue caracterizar la enzimología ligninolítica de especies de Armillaria en Patagonia y su capacidad de biodegradar compuestos contaminantes. Se cuantificaron las actividades lacasa y manganeso peroxidasa basales de 17 aislamientos y se evaluó su inducción por aditivos xenobióticos (guayacol y cobre) en el cultivo en 6 aislamientos representativos de las cuatro especies. Se determinaron los perfiles electroforéticos de isoenzimas de lacasa de 12 aislamientos y de tres aislamientos cultivados con los distintos xenobióticos. Se evaluó la capacidad de decoloración del colorante trifenilmetano verde de malaquita. La actividad lacasa, su perfil de isoenzimas, la susceptibilidad de ser inducida y la capacidad degradadora del colorante sugirieron ser caracteres quimiotaxonómicos útiles para Armillaria en Patagonia, no así la actividad manganeso peroxidasa que no resultó de interés a estos fines y registró actividades muy bajas o indetectables en concordancia con otras especies de la pudrición blanca citadas en bibliografía. Todas las especies demostraron ser efectivas en degradar el colorante verde de malaquita pero A. montagnei y A. novae-zelandiae exhibieron las mayores capacidades degradadoras, asociadas a las mayores actividades lacasa. En A. umbrinobrunnea y A. sparrei la degradación no estuvo asociada a actividades lacasa significativas, por lo que otras ligninasas u otros procesos oxidativos podrían ser los responsables de la transformación del contaminante. A. novae-zelandiae presentó la mayor tendencia a inducción de la enzima lacasa, resultando condicionante la presencia de aditivos xenobióticos para el registro de actividades enzimáticas elevadas en condiciones de cultivo; la inducción evidenció ser diferencial para algunas isoformas de lacasa en esta especie. El perfil electroforético reveló tres isoenzimas de lacasa, dos de ellas nuevas para el género, y la heterogeneidad interespecífica suficiente para resultar útil en caracterizar las especies patagónicas; ambos elementos resultan novedosos en el marco actual de conocimiento del género.

Global Distribution and Richness of Armillaria and Related Species Inferred From Public Databases and Amplicon Sequencing Datasets

Article

Full-text available

Nov 2021

Armillaria is a globally distributed fungal genus most notably composed of economically important plant pathogens that are found predominantly in forest and agronomic systems. The genus sensu lato has more recently received attention for its role in woody plant decomposition and in mycorrhizal symbiosis with specific plants. Previous phylogenetic analyses suggest that around 50 species are recognized globally. Despite this previous work, no studies have analyzed the global species richness and distribution of the genus using data derived from fungal community sequencing datasets or barcoding initiatives. To assess the global diversity and species richness of Armillaria, we mined publicly available sequencing datasets derived from numerous primer regions for the ribosomal operon, as well as ITS sequences deposited on Genbank, and clustered them akin to metabarcoding studies. Our estimates reveal that species richness ranges from 50 to 60 species, depending on whether the ITS1 or ITS2 marker is used. Eastern Asia represents the biogeographic region with the highest species richness. We also assess the overlap of species across geographic regions and propose some hypotheses regarding the drivers of variability in species diversity and richness between different biogeographic regions.

Interactions Between Weather-Related Disturbance and Forest Insects and Diseases in the Southern United States Disclaimer The Authors: Interactions Between Weather-Related Disturbance and Forest Insects and Diseases in the Southern United States

Technical Report

Full-text available

Aug 2020

Forests in the Southern United States experience a wide variety of weather-related disturbances, from small-scale events which have management implications for one or a few landowners to major hurricanes impacting many ownerships across multiple States. The immediate impacts of catastrophic weather disturbance are obvious-trees are killed, stressed, or damaged due to wind, flooding, ice, hail, or some combination of events. How forests respond to disturbance depends on several factors such as forest types and attributes, ecoregion, local pressure from invasive plants, preexisting infestations of pests and pathogens, prior disturbance events, and other variables which interact in complex ways, influencing successional dynamics and management decisions. In this review, we synthesize the major weather perturbations affecting the forests of the Southern United States and current state of the knowledge surrounding interactions between these events, forest pests, and forest diseases. We present a compilation of non-quantitative observations between 1955 and 2018 from annual U.S. Department of Agriculture Forest Service "Major Forest Insect and Disease Conditions in the United States" reports describing where insects or diseases were found on trees that were stressed by weather disturbances. Two conceptual models are presented, one describing changes in forest structure and composition, and a generalized model of herbivorous pest population fluctuations following different severity levels of disturbance. Finally, we propose 11 questions that require additional research to better inform sustainable forest management decisions in preparation for and in response to catastrophic weather events.

Molecular identification and phylogeny of Armillaria isolates from South America and Indo-Malaysia

Article

Mar 2003

Armillaria root rot is a serious disease, chiefly of woody plants, caused by many species of Armillaria that occur in temperate, tropical and subtropical regions of the world. Very little is known about Armillaria in South America and Southeast Asia, although Armillaria root rot is well known in these areas. In this study, we consider previously unidentified isolates collected from trees with symptoms of Armillaria root rot in Chile, Indonesia and Malaysia. In addition, isolates from basidiocarps resembling A. novae-zelandiae and A. limonea, originating from Chile and Argentina, respectively, were included in this study because their true identity has been uncertain. All isolates in this study were compared, based on their similarity in ITS sequences with previously sequenced Armillaria species, and their phylogenetic relationship with species from the Southern Hemisphere was considered. ITS sequence data for Armillaria also were compared with those available at GenBank. Parsimony and distance analyses were conducted to determine the phylogenetic relationships between the unknown isolates and the species that showed high ITS sequence similarity. In addition, IGS-1 sequence data were obtained for some of the species to validate the trees obtained from the ITS data set. Results of this study showed that the ITS sequences of the isolates obtained from basidiocarps resembling A. novae-zelandiae are most similar to those for this species. ITS sequences for isolates from Indonesia and Malaysia had the highest similarity to A. novae-zelandiae but were phylogenetically separated from this species. Isolates from Chile, for which basidiocarps were not found, were similar in their ITS and IGS-1 sequences to the isolate from Argentina that resembled A. limonea. These isolates, however, had the highest ITS and IGS-1 sequence similarity to authentic isolates of A. luteobubalina and were phylogenetically more closely related to this species than to A. limonea.

Mosaic fungal individuals have the potential to evolve within a single generation

Article

Full-text available

Oct 2020

Although cells of mushroom-producing fungi typically contain paired haploid nuclei (n + n), most Armillaria gallica vegetative cells are uninucleate. As vegetative nuclei are produced by fusions of paired haploid nuclei, they are thought to be diploid (2n). Here we report finding haploid vegetative nuclei in A. gallica at multiple sites in southeastern Massachusetts, USA. Sequencing multiple clones of a single-copy gene isolated from single hyphal filaments revealed nuclear heterogeneity both among and within hyphae. Cytoplasmic bridges connected hyphae in field-collected and cultured samples, and we propose nuclear migration through bridges maintains this nuclear heterogeneity. Growth studies demonstrate among- and within-hypha phenotypic variation for growth in response to gallic acid, a plant-produced antifungal compound. The existence of both genetic and phenotypic variation within vegetative hyphae suggests that fungal individuals have the potential to evolve within a single generation in response to environmental variation over time and space.

One stop shop IV: taxonomic update with molecular phylogeny for important phytopathogenic genera: 76–100 (2020)

Article

Full-text available

Sep 2020
FUNGAL DIVERS

This is a continuation of a series focused on providing a stable platform for the taxonomy of phytopathogenic fungi and fungus-like organisms. This paper focuses on one family: Erysiphaceae and 24 phytopathogenic genera: Armillaria, Barriopsis, Cercospora, Cladosporium, Clinoconidium, Colletotrichum, Cylindrocladiella, Dothidotthia,, Fomitopsis, Ganoderma, Golovinomyces, Heterobasidium, Meliola, Mucor, Neoerysiphe, Nothophoma, Phellinus, Phytophthora, Pseudoseptoria, Pythium, Rhizopus, Stemphylium, Thyrostroma and Wojnowiciella. Each genus is provided with a taxonomic background, distribution, hosts, disease symptoms, and updated backbone trees. Species confirmed with pathogenicity studies are denoted when data are available. Six of the genera are updated from previous entries as many new species have been described.

The Infection Process of Armillaria mellea and Armillaria solidipes

Article

Aug 2020

Armillaria mellea and A. solidipes are two of the primary causal agents of Armillaria root rot (ARR) in over 500 woody hosts. Although extensive research on this disease has been conducted over the past few decades, finding controls for ARR has been challenging. This is largely due to the lack of knowledge of the fungal infection and host response processes. It is important to understand the infection process in order to develop new strategies to control the disease. In this review, the initial steps of the infection process of A. mellea and A. solidipes are discussed, with focus on fungal attachment and penetration. A mucilaginous substance produced at the rhizomorph tip is thought to aid attachment of the pathogen to host. Toxins and cell wall degrading enzymes produced by the fungus together with mechanical pressure generated by the rhizomorph is speculated to support fungal penetration. However, a detailed description of the Armillaria spp. infection process is lacking in the literature, and this illustrates the need for further studies.

Delineation and Biology of Clones of Armillaria Ostoyae, A. Gemina and A. Calvescens

Article

Mar 1993

Diploid isolates of Armillaria were collected from a 50 × 25 m plot at each of two sites in the White Mountains, New Hampshire. All living and dead trees were examined for rhizomorphs, mycelial fans and decay. Isolates were identified to species using diploid-haploid pairings, and clones were delineated using somatic incompatibility and six isozyme markers. At a predominantly spruce-fir site, only A. ostoyae was identified and evidence suggested that at least 25 trees (10%) were pathogenically colonized. Isolates from 39 trees were divided into six somatic incompatibility groups; the largest somatic incompatibility group had colonized at least 17 trees. At a mixed conifer-hardwood site, three species of Armillaria were identified. Six somatic incompatibility groups of A. ostoyae were identified among isolates from 32 of 281 trees; the largest somatic incompatibility group colonized 14 trees and was at least 25 m in diameter. At least 14 of the 32 trees from which A. ostoyae was identified were pathogenically colonized. Armillaria gemina (31 trees) and A. calvescens (29 trees) were isolated mostly from epiphytic rhizomorphs on hardwoods, were apparently pathogenic on four of the trees, and were each divided into two somatic incompatibility groups. Two juxtaposed somatic incompatibility groups of A. ostoyae had identical isozyme electromorphs, but each of the other somatic incompatibility groups had an unique combination of electromorphs. The distribution pattern of the somatic incompatibility groups and correspondence with isozyme electromorphs supported the hypothesis that the somatic incompatibility groups represent asexually spreading clones. At both sites, there was little intermingling of clones of the same species; however, at the mixed conifer-hardwood site clones of the different Armillaria species overlapped considerably.

Culturable microfungi inhibitory to A rmillaria rhizomorph formation from Fagus sylvatica stump roots and soil

Article

Feb 2018

Culturable fungi from 28 fungal communities were isolated from soil, rhizosphere and thick (1 cm diam.) roots of living beech (Fagus sylvatica) trees and their stumps 1–3 years after felling. All fungi were morphotyped and identified morphologically. The frequency of fungi was 2–5× greater in stumps than in living trees. The diversity of fungi was similar in living trees and stumps. The majority of fungal species that occurred at greater frequency on/in roots of stumps reduced the growth of Armillaria ostoyae and to a smaller extent of A. gallica rhizomorphs in a soil substrate in vitro. It is suggested that the mycobiota of roots may constrain the colonization of F. sylvatica by A. ostoyae rather than by A. gallica. The significance of these findings in the epidemiology of Armillaria in beech forests is discussed.

Associations Between Armillaria Species and Host Plants in U.K. Gardens

Article

Full-text available

Jul 2017
PLANT DIS

Honey fungus (Armillaria spp.) root rot is the disease most frequently inquired about by U.K. gardeners to the Royal Horticultural Society. Armillaria epidemiology has been studied within forestry and agriculture, but data are lacking within gardens, which have greater host plant diversity than orchards and vineyards and greater disturbance than woodlands. Which Armillaria species are responsible for garden disease, and how the broad range of susceptible ornamentals are differentially affected is not known. To address this, isolates of Armillaria were obtained from dead and dying plants from across the U.K. over a 4-year period (2004 to 2007). Species were identified by PCR-RFLP for IGS, and further verified by species-specific PCR for EF-1 α. Of the seven species known in the U.K., three were identified: A. mellea (83.1%), A. gallica (15.8%), and A. ostoyae (1.1%). Armillaria was isolated from trees, shrubs, and nonwoody plants including bulbs and vegetables, with newly recorded hosts listed herein. A. mellea was associated with infections of multiple hosts, and with all infections of the most common host, Ligustrum. In sites where more than one Armillaria species was found, the combination was of A. mellea and A. gallica, raising questions regarding the interactions of these species in U.K. gardens. © 2017, American Phytopathological Society. All rights reserved.

Haploid vegetative mycelia of Armillaria gallica show among-cell-line variation for growth and phenotypic plasticity

Article

Sep 2005

Vegetative mycelial cells of Armillaria are expected to have diploid nuclei. Cells from a single mycelium therefore would not be expected to differ from one another for ecologically relevant quantitative traits. We isolated two sets of basidiome cell lines (from spores and stipe cells) and one set of vegetative cell lines (from an attached rhizomorph) from a single contiguous Armillaria gallica mycelium. We isolated a second set of vegetative cell lines from the soil 20 cm from the above basidiomerhizomorph complex. In all four sets of cell lines in situ DAPI-DNA measurements showed cells are haploid and quantitative-trait analyses of cell lines grown at different water potentials revealed high levels of among-cell-line genetic variation for both growth and phenotypic plasticity. Haploidy and the existence of ecologically relevant genetic variation within vegetative individuals are unexpected and mean that a process similar to evolutionary adaptation could take place within the soma of a genetic individual. We believe this is a key to understanding how large A. gallica mycelia survive exposure to variation in ecological conditions during lives that potentially span several tree (host) generations.

Survival and yield of Douglas-fir in the Cedar-Hemlock ecosystem of the southern interior of British Columbia.

Article

Full-text available

Sep 2016
FORESTRY

M. G. Cruickshank

Extended tree lifespans require investments against decay, herbivory, wind and fire. Tree root diseases are global pathogens impacting growth and survival over a large range of tree species. The commercially important conifer Douglas-fir highlights conditions affecting its survival and growth in nine planted and four natural study sites in British Columbia. Planted Douglas-fir ranged from 20-40 years, and natural stands from 63-110 years. Average survival for all tree species in planted stands was 86% after 30 years, with 80% mortality from Armillaria ostoyae. Average survival of Douglas-fir in natural stands was 60% at age 90 with 86% mortality from A. ostoyae. Mortality began in planted stands about tree ages 6-10, and in most natural stands about tree ages 55-65. Stand age, site index, proportion of Douglas-fir, precipitation, and temperature, but not stand density, accounted for most of the hazard. Percent dead trees were correlated with percent plot basal area losses at 1 to 1 ratio in both stand types. Larger planted Douglas-fir trees had greater hazard sooner up to age 30 than smaller trees. Rapid early tree growth likely caused extensive root contact with fungal stump inoculum. Older and larger trees were affected by interacting climate limitations and disease status.

Pest Risk Assessment of the Importation into the United States of Unprocessed Eucalyptus Logs and Chips from South America

Technical Report

Full-text available

Apr 2001

In this report, we assess the unmitigated pest risk potential of importing Eucalyptus logs and chips from South America into the United States. To do this, we estimated the likelihood and consequences of introducing representative insects and pathogens of concern. Nineteen individual pest risk assessments were prepared, eleven dealing with insects and eight with pathogens. The selected organisms were representative examples of insects and pathogens found on the foliage, on the bark, in the bark, and in the wood of Eucalyptus spp. Among the insects and pathogens assessed, eight were rated a high risk potential: purple moth (Sarsina violescens), scolytid bark and ambrosia beetles (Scolytopsis brasiliensis, Xyleborus retusus, Xyleborus biconicus, Xyleborus spp.), carpenterworm (Chilecomadia valdiviana) on Eucalyptus nitens, round-headed wood borers (Chydarteres striatus, Retrachyderes thoracicus, Trachyderes spp., Steirastoma breve, Stenodontes spinibarbis), eucalyptus longhorned borer (Phoracantha semipunctata), Botryosphaeria cankers (Botryosphaeria dothidea, Botryosphaeria obtusa, Botryosphaeria ribi), Ceratocystis canker (Ceratocystis fimbriata), and pink disease (Erythricium salmonicolor). A moderate pest risk potential was assigned to eleven other organisms or groups of organisms: eucalypt weevils (Gonipterus spp.), carpenterworm (Chilecomadia valdiviana) on two Eucalyptus species other than E. nitens, platypodid ambrosia beetle (Megaplatypus parasulcatus), yellow phorancantha borer (Phoracantha recurva), subterranean termites (Coptotermes spp., Heterotermes spp.), foliar diseases (Aulographina eucalypti, Cryptosporiopsis eucalypti, Cylindrocladium spp., Phaeophleospora spp., Mycosphaerella spp.), eucalyptus rust (Puccinia psidii), Cryphonectria canker (Cryphonectria cubensis), Cytospora cankers (Cytospora eucalypticola, Cytospora eucalyptina), Coniothyrium canker (Coniothyrium zuluense), and root and stem rots (Armillaria spp., Phellinus spp., Ganoderma sp., Gymnopilus spectabilis). For those organisms of concern that are associated with logs and chips of South American Eucalyptus spp., specific phytosanitary measures may be required to ensure the quarantine safety of proposed importations.

Depois do fogo

Chapter

Full-text available

Jan 2007

Opportunistically Pathogenic Root Rot Fungi: Armillaria Species

Chapter

Jan 2003

Numerous gap-model studies have attempted to predict responses of tree populations to climate change. Although these models incorporate various disturbance factors, the multifaceted influences of structural-root disease activity on gap dynamics have not been included [e.g., (2000)]. The fact that apparently similar models yield very different projections for the same forest [e.g., (1997)] suggests that most of these models are incomplete and/or may be inappropriately formulated (Bachelet and Neilson 2000). The existence of belowground root gaps corresponding to aboveground canopy gaps and their influence on plant competition and establishment have also received little attention [see (1997)]. Yet, Armillaria root disease and other structural-root diseases have been associated with gap dynamics [e.g., (1988); (1993); (1993), 1995); (1997); (2000)].

Controlling root and butt rot diseases in alpine European forests

Article

Feb 2010

Paolo Gonthier

Alpine European forests comprising of conifers and broadleaf trees at lower altitudes are facing major problems of poor regeneration and occurrence of numerous fungal diseases. Fungal organisms like Armillaria mellea and Heterobasidion annosum are taking their toll on a large number of conifers. These two pathogens are responsible for most of the root and butt rot diseases in natural forest stands. Diagnosis of disease can be done by macro/micromorphology of basidiomata. The wood-inhabiting fungi can also be identifi ed by taxon-specifi c primers using PCR. This chapter deals with various biological and cultural control strategies and the promotion of disease-tolerant plants, which can reduce the occurrence of diseases. Integrated disease management plans are suggested for different species as found suitable in the Aosta Valley of the western Italian Alps.

Occurrence and distribution of Armillaria gallica genets in a declining oak stand of southern Italy

Article

Full-text available

Aug 2003

Outbreaks of Armillaria root rot in conifer plantations and declining oak stands are frequently due to the spread of the fungus in the soil over long periods. This paper examines the occurrence and distribution of Armillaria genets in a declining mixed oak stand of southern Italy. Samples of rhizomorphs, mycelial mats and fruit bodies of Armillaria were collected from the soil, stumps, and living and dead trees. A total of 111 Armillaria isolates were collected, all belonging to the species A. gallica. They were grouped in 28 genets by somatic incompatibility. The largest genet covered an area of about 2.6 ha with a linear extent of 300 m. On the basis of an estimated 0.5 m annual growth in the soil, its age was assumed to be about 3 centuries. The results confirm the ability of A. gallica to remain alive and stable in a large area over a long time.

Suitability of test tree method in assessment of threat to pine stands posed by Armillaria spp

Article

Full-text available

Jan 2006

Wojciech Szewczyk

In the Złotów Forest District 5 pine stands were selected and in each of which 4 observation plots were established each, consisting of 50 trees growing in clusters. The study consisted in one count of dead trees per year conducted in observation plots and in the whole experimental area. Results of the 3-year study showed the applied test tree method is not suitable in the assessment of threat to age class I pine stands posed by Ar-millaria fungi.

Distribution, ecology, host range and possible managemt of Armillaria species in Albania

Book

Full-text available

May 2008

Bashkim Mal Lushaj

The species identification of 645 Armillaria isolates was made in a nation-wide survey in Albania. The material was collected from ca. 250 permanent plots, established for monitoring forest health, and from forests and gardens attacked by Armillaria. A. mellea s.s. was found on several coniferous and broadleaved trees in most areas examined, except above 1100-1200 m in northern Albania. It causes some damage to fir and oak species and in a lesser degree to other forest trees. It is also common and damaging in fruit orchards and vineyards. A. gallica was a common saprophyte or weak pathogen in coniferous and deciduous forests at altitudes from 600 to 1600 m, and less common at lower altitudes on oaks. A. ostoyae was rare in central and southern Albania, but common in northern Albania, causing significant damage to pine and other conifers, mostly at altitudes from 600 to 1800 m. A. cepistipes was recorded at altitudes from 800 to 1800 m as a saprophyte or weak pathogen on conifers and deciduous trees, mostly in beech and silver fir forests. A. tabescens was found preferably in oak forests at altitudes from sea level to 900 m. In fruit orchards it occasionally attacked almond and pear trees. A. borealis was found on a few localities in northernmost Albania, at altitudes from 800 to1800 m. A. Mediterranea was found on a few localities in souththernmost Albania, at altitudes from 0 to100 m. The possible management of Armillaria species is necessary for healing of forests, orchards, etc. During the years in Albania the possible management Armillaria species was carried out by means of: Inoculums’ Reduction; Resistant Species; and Increasing Host Vigor.

SC IE N T I MONITORING ARMILLARIA ROOT ROT IN YOUNG (UP TO 20 YRS) SCOTS PINE PLANTATIONS IN ZIELONKA FOREST DISTRICT

Article

Full-text available

In Zielonka Forest District seven Scots pine plantations monitored in 1998-2001 for Armillaria ostoyae and Heterobasidion annosum disease development proved affected mainly by the former pathogen. Observations of 200 trees per plantation (every spring and fall) showed there was no correlation between the morphological features and over ground symptoms and infestation of pines by the pathogens in question and mortality of trees. The young stands were threatened more by Armillaria than by Heterobasidion annosum s.s., yet the infestation by Armillaria decreased with age of trees while the infestation by Heterobasidion increased.

Inhibition of Armillaria and Heterobasidion growth by Penicillium adametzii isolated from Pinus sylvestris forest soil

Article

Dec 2012

Summary Penicillium adametzii significantly inhibited the growth of Heterobasidium annosum sensu stricto on 2% potato dextrose agar after 10 days at 20–25°C. Chloroform extracts from P. adametzii culture filtrate and from culture grown on rice often decreased the dry weight of Armillaria colony and diameter of Heterobasidion colony in vitro. The effect depended on species and isolate of Armillaria, Heterobasidion and P. adametzii and concentration of the extract. Higher concentration of chloroform extract increased the dry weight of stems and roots of Pinus sylvestris plants inoculated with either of two isolates of Armillaria ostoyae and one isolate of Armillaria gallica. Lower concentrations of chloroform extract increased the dry weight of stems and roots of P. sylvestris inoculated with another isolate of A. gallica. Culture filtrate of P. adametzii decreased the length of necrosis on P. sylvestris stem inoculated with either of two of four isolates of H. annosum s.s., but if applied 1 month before inoculation, it increased the length of necrosis caused by another H. annosum s.s. isolate. Twenty fractions from the P. adametzii chloroform extract were separated by thin layer chromatography. Carboxylic acids, flavonoids and glycosides were detected in chloroform extract of P. adametzii by high performance liquid chromatography/mass spectrometer analysis. This is the first report of interactions between P. adametzii and either Armillaria or Heterobasidion with P. sylvestris.

Relationship of site and stand characteristics to Armillaria root disease incidence on ponderosa pine in the Black Hills, South Dakota

Article

Apr 2012

Ponderosa pine (Pinus ponderosa) in the Black Hills National Forest, SD, USA, was surveyed for Armillaria root disease (ARD). The root pathogen Armillaria ostoyae occurred on ponderosa pine seedlings, saplings, pole‐size trees and large‐diameter trees. The mean incidence of aboveground disease symptoms by stem count was low (0.2%), but in certain areas, the incidence was higher, affecting the regeneration success and tree longevity. Symptomatic ponderosa pine were in areas characterized by having higher elevation, greater annual precipitation, more seedlings, bigger large‐diameter trees and greater odds of past harvesting activity than in areas without root disease. Stump density was positively spatially correlated with root disease incidence. No particular soil type was related to disease occurrence; though, in areas with symptomatic trees, soil available water holding capacity (AWC) was greater and soil permeability was less where root disease was present. Spatial analysis confirmed the relationships found in linear correlations, with soil AWC and stump density positively and soil permeability negatively correlated with per cent infected stems ha−1 and basal area infected.

Ecology and Disease in Natural Forests

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