First Report of the Invasive Ash Dieback Pathogen Hymenoscyphus fraxineus on Fraxinus excelsior and F. angustifolia in Serbia

In Serbia, unambiguous symptoms of ash dieback disease were for the first time observed in September 2015. Symptoms included dead shoots and occasionally small necrotic lesions in the bark accompanied by characteristic wood discoloration. Isolation of fungal cultures from symptomatic tissues of F. excelsior and F. angustifolia and their sequencing using the internal transcribed spacer of the rDNA (ITS rDNA) as a marker confirmed the presence of the ash dieback pathogen, Hymenoscyphus fraxineus

Arum-type of arbuscular mycorrhizae, dark septate endophytes and Olpidium spp. in fine roots of container-grown seedlings of Sorbus torminalis (Rosaceae)

The aim of this study was to determine the mycorrhizal status of nursery seedlings of the wild service tree (Sorbus torminalis), which belongs to the Rosaceae family. Its mycorrhizal associations are still fragmentarily known, and data from the few existing studies indicate that it forms ectomycorrhizal symbiosis (ECM). We analyzed the degree of mycorrhizal colonization of thirty 2-year-old container-grown S. torminalis nursery seedlings, which belonged to three single-tree progenies. The roots were dominated by arbuscular mycorrhizae (AM), with the morphology of the Arum-type containing arbuscules, vesicles and hyphae; however, no ECM structures were found. The degree of root colonization of the analyzed seedlings by AM fungi was 83.6% and did not differ significantly between the three single-tree progenies. In addition to AM, structures of dark septate endophytes (0.7%) and sporangia of Olpidium spp. (1.1%) were found in wild service tree roots. In agreement with previous studies, we confirmed arbuscular mycorrhizae for S. torminalis. Moreover, this is the first report that roots of this Sorbus species show the Arum-type morphology of AM and are associated with Olpidium species

Blue-stain development on Norway spruce logs under alpine conditions

Discoloration of the sapwood caused by blue-stain fungi on conifer logs during interim storage causes significant loss to the forest industry. The fungal infection is often associated with bark beetle attacks because the spores are transmitted by the beetles. They can also be disseminated by rain-splash and moist air. While there are methods to protect logs from sap-stain in wood yards, this is often not possible in the forest for practical and regulatory reasons. Timing of harvesting and timely transportation are often the only ways to prevent blue-stain. To estimate the urgency of transportation, knowledge of the growth of blue-stain fungi and its dependence on weather conditions is of great interest. The proportion of discolored sapwood on Norway spruce logs was recorded along a time series, together with weather data in two field experiments conducted in spring and summer at two alpine sites in Austria. A predictive model was developed to estimate the proportion of blue-stained sapwood based on the temperature sum to which the logs were exposed. After harvest in March, there was a time lag of 82 and 97 days at the two respective sites, caused by initially low temperatures, before discoloration started. In contrast, sap-stain occurred 14 days after the harvest in June, when warm conditions prevailed from the start. The nonlinear least square regression model can help to estimate a window of opportunity to transport wood before it loses its value and serves as a sub model for lead time estimation within logistic decision support systems

Population structure and diversity of an invasive pine needle pathogen reflects anthropogenic activity

Dothistroma septosporum is a haploid fungal pathogen that causes a serious needle blight disease of pines, particularly as an invasive alien species on Pinus radiata in the Southern Hemisphere. During the course of the last two decades, the pathogen has also incited unexpected epidemics on native and non-native pine hosts in the Northern Hemisphere. Although the biology and ecology of the pathogen has been well documented, there is a distinct lack of knowledge regarding its movement or genetic diversity in many of the countries where it is found. In this study we determined the global population diversity and structure of 458 isolates of D. septosporum from 14 countries on six continents using microsatellite markers. Populations of the pathogen in the Northern Hemisphere, where pines are native, displayed high genetic diversities and included both mating types. Most of the populations from Europe showed evidence for random mating, little population differentiation and gene flow between countries. Populations in North America (USA) and Asia (Bhutan) were genetically distinct but migration between these continents and Europe was evident. In the Southern Hemisphere, the population structure and diversity of D. septosporum reflected the anthropogenic history of the introduction and establishment of plantation forestry, particularly with Pinus radiata. Three introductory lineages in the Southern Hemisphere were observed. Countries in Africa, that have had the longest history of pine introductions, displayed the greatest diversity in the pathogen population, indicating multiple introductions. More recent introductions have occurred separately in South America and Australasia where the pathogen population is currently reproducing clonally due to the presence of only one mating type.The Department of Science and Technology (DST)/National Research Foundation (NRF), the Tree Protection Co-operative Programme (TPCP), the Claude Leon Foundation and the THRIP initiative of the Department of Trade and Industry, South Africa.http://onlinelibrary.wiley.comjournal/10.1002/(ISSN)2045-7758am201

The Ophiostoma clavatum species complex : a newly defined group in the Ophiostomatales including three novel taxa

Two species of blue-stain fungi with similar morphologies, Ophiostoma brunneociliatum and O. clavatum, are associates of bark beetles infesting Pinus spp. in Europe. This has raised questions whether they represent distinct taxa. Absence of herbarium specimens and contaminated or mistakenly identified cultures of O. brunneo-ciliatum and O. clavatum have accentuated the uncertainty regarding their correct identification. The aim of this study was to reconsider the identity of European isolates reported as O. brunneo-ciliatum and O. clavatum by applying DNA-based identification methods, and to provide appropriate type specimens for them. Phylogenetic analyses of the ITS, βT, TEF-1 and CAL gene sequences revealed that the investigated isolates represent a complex of seven cryptic species. The study confirmed that ITS data is insufficient to delineate species in some Ophiostoma species clusters. Lectotypes and epitypes were designated for O. clavatum and O. brunneo-ciliatum, and three new species, O. brunneolum, O. macroclavatum and O. pseudocatenulatum, were described in the newly defined O. clavatum-complex. The other two species included in the complex are O. ainoae and O. tapionis. The results suggest co-evolution of these fungi in association with specific bark beetles. The results also confirm the identity of the fungus associated with the pine bark beetle Ips acuminatus as O. clavatum, while O. brunneo-ciliatum appears to be mainly associated with another pine bark beetle, Ips sexdentatus.The University of Helsinki and the Emil Aaltonen Foundation, Finland; the University of Pretoria, the members of the Tree Protection Co-operative Programme (TPCP) and the THRIP initiative of the Department of Trade and Industry, South Africa; the Ministry of Science and Higher Education of the Republic of Poland; Ministero dell’Istruzione, dell’Università e della Ricerca (PRIN 200774ENMR ‘Climatic change and Italian pine pests: a model study’), Italy; the European Union’s Seventh Framework Programme FP7/2007–2013 (KBBE 2009-3) under grant agreement 245268 ISEFOR; and the Norwegian Biodiversity Information Centre (pnr. 70184233).http://link.springer.com/journal/104822017-05-31hb2016Microbiology and Plant Patholog

Advanced spectroscopy-based phenotyping offers a potential solution to the ash dieback epidemic

Natural and urban forests worldwide are increasingly threatened by global change resulting from human-mediated factors, including invasions by lethal exotic pathogens. Ash dieback (ADB), incited by the alien invasive fungus Hymenoscyphus fraxineus, has caused large-scale population decline of European ash (Fraxinus excelsior) across Europe, and is threatening to functionally extirpate this tree species. Genetically controlled host resistance is a key element to ensure European ash survival and to restore this keystone species where it has been decimated. We know that a low proportion of the natural population of European ash expresses heritable, quantitative resistance that is stable across environments. To exploit this resource for breeding and restoration efforts, tools that allow for effective and efficient, rapid identification and deployment of superior genotypes are now sorely needed. Here we show that Fourier-transform infrared (FT-IR) spectroscopy of phenolic extracts from uninfected bark tissue, coupled with a model based on soft independent modelling of class analogy (SIMCA), can robustly discriminate between ADB-resistant and susceptible European ash. The model was validated with populations of European ash grown across six European countries. Our work demonstrates that this approach can efficiently advance the effort to save such fundamental forest resource in Europe and elsewhere

Phenotypes of Non-Attached Pseudomonas aeruginosa Aggregates Resemble Surface Attached Biofilm

For a chronic infection to be established, bacteria must be able to cope with hostile conditions such as low iron levels, oxidative stress, and clearance by the host defense, as well as antibiotic treatment. It is generally accepted that biofilm formation facilitates tolerance to these adverse conditions. However, microscopic investigations of samples isolated from sites of chronic infections seem to suggest that some bacteria do not need to be attached to surfaces in order to establish chronic infections. In this study we employed scanning electron microscopy, confocal laser scanning microscopy, RT-PCR as well as traditional culturing techniques to study the properties of Pseudomonas aeruginosa aggregates. We found that non-attached aggregates from stationary-phase cultures have comparable growth rates to surface attached biofilms. The growth rate estimations indicated that, independently of age, both aggregates and flow-cell biofilm had the same slow growth rate as a stationary phase shaking cultures. Internal structures of the aggregates matrix components and their capacity to survive otherwise lethal treatments with antibiotics (referred to as tolerance) and resistance to phagocytes were also found to be strikingly similar to flow-cell biofilms. Our data indicate that the tolerance of both biofilms and non-attached aggregates towards antibiotics is reversible by physical disruption. We provide evidence that the antibiotic tolerance is likely to be dependent on both the physiological states of the aggregates and particular matrix components. Bacterial surface-attachment and subsequent biofilm formation are considered hallmarks of the capacity of microbes to cause persistent infections. We have observed non-attached aggregates in the lungs of cystic fibrosis patients; otitis media; soft tissue fillers and non-healing wounds, and we propose that aggregated cells exhibit enhanced survival in the hostile host environment, compared with non-aggregated bacterial populations

First Reports of Silver Fir Blue Staining Ophiostomatoid Fungi Associated with Pityokteines Spinidens

Pityokteines spinidens commonly occurs in Europe where it infests Silver fir and occasionally other conifers. Together with the two additional Pityokteines species (P. curvidens and P. vorontzowi) it has been reported as an important factor in Silver fir decline in some parts of Europe. Bark beetles are known to be associated with diverse guilds of arthropods and microorganisms of which phoretic mites and ophiostomatoid fungi are among the best-known associates. Some ophiostomatoid fungi associated with bark beetles display high levels of virulence to their host trees and they are thus suspected to aid their bark beetle vectors in overcoming the defense mechanisms of living hosts. Increased local populations of P. curvidens, P. spinidens and P. vorontzowi have been recently noted in conifer forests in various parts of Croatia, resulting in high damage levels on Silver fir. This increase in the importance of Pityokteines species as forest pests of Silver fir in Croatia, prompted research on the biology of these bark beetles species and on their mite and fungal associates. Preliminary reports of ophiostomatoid fungi associated with P. spinidens resulted from the inspections of bark beetle galleries in trees at the site Litori} (Gorski Kotar, Croatia) where severe case of Silver fir decline took place. Six ophiostomatoid fungi were isolated from the galleries of P. spinidens. These included Ceratocystiopsis minuta, Ceratocystiopsis cf. alba, Graphium cf. fimbriisporum, Ophiostoma cf. cucullatum, Ophiostoma piceae sensu lato and a Pesotum species. Ophiostoma cf. cucullatum was the most common species based on the occurrence of fungal structures in the insect galleries