Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2022
Authors
Nina Elisabeth Nagy Hans Ragnar Norli Monica Fongen Runa Berg Østby Inger Heldal Jahn Davik Ari HietalaAbstract
Tree defense against xylem pathogens involves both constitutive and induced phenylpropanoids and terpenoids. The induced defenses include compartmentalization of compromised wood with a reaction zone (RZ) characterized by polyphenol deposition, whereas the role of terpenoids has remained poorly understood. To further elucidate the tree–pathogen interaction, we profiled spatial patterns in lignan (low-molecular-weight polyphenols) and terpenoid content in Norway spruce (Picea abies) trees showing heartwood colonization by the pathogenic white-rot fungus Heterobasidion parviporum. There was pronounced variation in the amount and composition of lignans between different xylem tissue zones of diseased and healthy trees. Intact RZ at basal stem regions, where colonization is the oldest, showed the highest level and diversity of these compounds. The antioxidant properties of lignans obviously hinder oxidative degradation of wood: RZ with lignans removed by extraction showed significantly higher mass loss than unextracted RZ when subjected to Fenton degradation. The reduced diversity and amount of lignans in pathogen-compromised RZ and decaying heartwood in comparison to intact RZ and healthy heartwood suggest that α-conindendrin isomer is an intermediate metabolite in lignan decomposition by H. parviporum. Diterpenes and diterpene alcohols constituted above 90% of the terpenes detected in sapwood of healthy and diseased trees. A significant finding was that traumatic resin canals, predominated by monoterpenes, were commonly associated with RZ. The findings clarify the roles and fate of lignan during wood decay and raise questions about the potential roles of terpenoids in signal transduction, synthesis, and translocation of defense compounds upon wood compartmentalization against decay fungi.
2021
Abstract
No abstract has been registered
Abstract
The relationship between the ecological success of needle pathogens of forest trees and species richness of co-inhabiting endophytic fungi is poorly understood. One of the most dangerous foliar pathogens of pine is Dothistroma septosporum, which is a widely spread threat to northern European forests. We sampled two Pinus sylvestris sites in Estonia and two in Norway in order to analyse the relations between the abundance of D. septosporum and overall fungal richness, specific fungal species composition, time of season, needle age and position in the canopy. In both countries, the overall species richness of fungi was highest in autumn, showing a trend of increase with needle age. The overall species richness in the second-year needles in Estonia and third-year needles in Norway was similar, suggesting that a critical colonization threshold for needle shed in P. sylvestris is breached earlier in Estonia than in Norway. The fungal species richness in P. sylvestris needles was largely affected by Lophodermium conigenum. Especially in older needles, the relative abundance of L. conigenum was significantly higher in spring compared to summer or autumn. The timing of recruitment and colonization mechanisms of different foliage endophytes are shortly discussed.
Authors
Elisabeth Pötzelsberger Martin M. Gossner Ludwig Beenken Anna Gazda Michal Petr Tiina Ylioja Nicola La Porta Dimitrios N. Avtzis Elodie Bay Maarten De Groot Rein Drenkhan Mihai-Leonard Duduman Rasmus Enderle Margarita Georgieva Ari Hietala Björn Hoppe Herve Jactel Kristjan Jarni Srđan Keren Zsolt Keseru Marcin Koprowski Andrej Kormuťák María Josefa Lombardero Aljona Lukjanova Vitas Marozas Edurad Mauri Maria Cristina Monteverdi Per Holm Nygaard Nikica Ogris Nicolai Olenici Christophe Orazio Bernhard Perny Glória Pinto Michael Power Radoslaw Puchalka Hans Peter Ravn Ignacio Sevillano Sophie Stroheker Paul Taylor Panagiotis Tsopelas Josef Urban Kaljo Voolma Marjana Westergren Johanna Witzell Olga Zborovska Milica ZlatkovicAbstract
For non-native tree species with an origin outside of Europe a detailed compilation of enemy species including the severity of their attack is lacking up to now. We collected information on native and non-native species attacking non-native trees, i.e. type, extent and time of first observation of damage for 23 important non-native trees in 27 European countries. Our database includes about 2300 synthesised attack records (synthesised per biotic threat, tree and country) from over 800 species. Insects (49%) and fungi (45%) are the main observed biotic threats, but also arachnids, bacteria including phytoplasmas, mammals, nematodes, plants and viruses have been recorded. This information will be valuable to identify patterns and drivers of attacks, and trees with a lower current health risk to be considered for planting. In addition, our database will provide a baseline to which future impacts on non-native tree species could be compared with and thus will allow to analyse temporal trends of impacts.
Abstract
The scope of this study was to provide an update on fluoride (F) emission effects on vegetation around three aluminium smelters. We visited Årdal and Sunndal smelters in 2019-2020 and Mosjøen in 2020, assessed and documented the visual symptoms of F-damage on vegetation and related these to detected values of F in plant tissue. Three plant species showed qualities as useful indicators: Rowan, pine and St. John’s wort. Because male-fern accumulated extreme F-values and showed clear grazing damage, the monitoring of this species may be warranted because of the potential health hazard for the grazing animals. In Årdal and Sunndal, during 2019 and 2020, we detected the highest F-values in male-fern, ranging from 94 to 925 mg F/kg. In rowan, the highest F-concentration was detected in trees growing within the Årdal smelter (1161 mg F/kg) but on all other locations the F-concentrations in rowan ranged from 4 to 327 mg F/kg. In pine, the F-concentrations ranged from 6-351 mg F/kg for all needle ages, but older needles always accumulated more F than younger ones. In St. John’s wort the accumulated F-values ranged from 10-84 mg F/kg. At all smelters there was a gradient of decreasing F-concentration in vegetation with increasing distance from the smelter. F-emissions in Årdal (12 and 11 kg F/hour in 2019 and 2020, respectively) and in Sunndal during 2019 (12 kg F/hour) were only slightly higher than the recommended limits (10 kg F/hour) for damage on vegetation, while in Mosjøen the F-emissions were 7 kg F/hour in 2020. The presence of F-damage on vegetation was consistent with the reported emission-levels. On basis of this evaluation, reductions in emissions are still advisable in Årdal and Sunndal, while the situation is acceptable in Mosjøen.
2020
Authors
Olalla Díaz-Yáñez Blas Mola-Yudego Volkmar Timmermann Mari Mette Tollefsrud Ari Hietala Jonas OlivaAbstract
Determining the impacts of invasive pathogens on tree mortality and growth is a difficult task, in particular in the case of species occurring naturally at low frequencies in mixed stands. In this study, we quantify such effects by comparing national forest inventory data collected before and after pathogen invasion. In Norway, Fraxinus excelsior is a minor species representing less than 1% of the trees in the forests and being attacked by the invasive pathogen Hymenoscyphus fraxineus since 2006. By studying deviations between inventories, we estimated a 74% higher-than-expected average ash mortality and a 13% slower-than-expected growth of the surviving ash trees, indicating a lack of compensation by the remaining ash. We could confidently assign mortality and growth losses to ash dieback as no mortality or growth shifts were observed for co-occurring tree species in the same plots. The mortality comparisons also show regional patterns with higher mortality in areas with the longest disease history in Norway. Considering that ash is currently mostly growing in mixed forests and that no signs of compensation were observed by the surviving ash trees, a significant habitat loss and niche replacement could be anticipated in the mid-term.
Authors
Ahto Agan Rein Drenkhan Kalev Adamson Leho Tedersoo Halvor Solheim Isabella Børja Iryna Matsiakh Volkmar Timmermann Nina Elisabeth Nagy Ari HietalaAbstract
European ash (Fraxinus excelsior) is threatened by the invasive ascomycete Hymenoscyphus fraxineus originating from Asia. Ash leaf tissues serve as a route for shoot infection but also as a sporulation substrate for this pathogen. Knowledge of the leaf niche partitioning by indigenous fungi and H. fraxineus is needed to understand the fungal community receptiveness to the invasion. We subjected DNA extracted from unwashed and washed leaflets of healthy and diseased European ash to PacBio sequencing of the fungal ITS1-5.8S-ITS2 rDNA region. Leaflets from co-inhabiting rowan trees (Sorbus aucuparia) served as a reference. The overlap in leaflet mycobiomes between ash and rowan was remarkably high, but unlike in rowan, in ash leaflets the sequence read proportion, and the qPCR-based DNA amount estimates of H. fraxineus increased vigorously towards autumn, concomitant with a significant decline in overall fungal richness. The niche of ash and rowan leaves was dominated by epiphytic propagules (Vishniacozyma yeasts, the dimorphic fungus Aureobasidion pullulans and the dematiaceous hyphomycete Cladosporium ramotenellum and H. fraxineus), and endophytic thalli of biotrophs (Phyllactinia and Taphrina species), the indigenous necrotroph Venturia fraxini and H. fraxineus. Mycobiome comparison between healthy and symptomatic European ash leaflets revealed no significant differences in relative abundance of H. fraxineus, but A. pullulans was more prevalent in symptomatic trees. The impacts of host specificity, spatiotemporal niche partitioning, species carbon utilization profiles and life cycle traits are discussed to understand the ecological success of H. fraxineus in Europe. Further, the inherent limitations of different experimental approaches in the profiling of foliicolous fungi are addressed.
Authors
Christer Magnusson Ari Hietala Per Hansen Eva Solbjørg Flo Heggem Irene Rasmussen Birgit Schaller Marte Persdatter Tangvik Ben Z HellalAbstract
I 2019 års kartlegging av furuvednematoden Bursaphelenchus xylophilus i Norge ble 400 prøver tatt fra hogstavfall og vindfall av Pinus sylvestris L. med angrep av furubukk Monochamus spp. Prøvene ble tatt ut i Akershus, Buskerud, Østfold, Telemark, Aust-Agder og Vest-Agder. Prøvene som besto av flis ble inkubert ved +25oC i to uker før de ble ekstrahert med Baermanntrakt og undersøkt i mikroskop. Furuvednematoden B. xylophilus ble ikke påvist i prøvene, men den naturlig forekommende arten Bursaphelenchus mucronatus kolymensis ble oppdaget i fire prøver fra Agderfylkene. Feller med feromoner for fangst av furubukk ble satt opp i Hedmark (Elverum, Romedal, Stange og ved Geitholmsjøen), Møre og Romsdal (Kvanne) og Østfold (Fredrikstad og Vestby). I laboratoriet ble billene kuttet i biter og ekstrahert med en modifisert Baermanntrakt. Suspensjonen fra ekstraksjonene ble undersøkt i stereomikroskop for forekomst av infektive stadier av Bursaphelenchus spp.. Ingen nematoder kunne påvises i de 106 undersøkte billene. I perioden 2000 – 2019 er totalt 8123 vedprøver analysert. Flest prøver er tatt i Østfold, fulgt av Hedmark, Telemark, Buskerud og Aust-Agder. I kartleggingen 2019 ble B. mucronatus kolymensis påvist i fire av de 400 vedprøvene, tilsvarende en frekvens på 0,01 (1 %). For hele perioden 2000 - 2019 ble Bursaphelenchus mucronatus kolymensis + B. macromucronatus, oppdaget i 73 av 8123 vedprøver som gir en eteksjonsfrekvens på 0,009 (ca. 1 %). I perioden 2014-2019 har Bursaphelenchus mucronatus kolymensis blitt påvist fem av totalt 581 biller, som gir den samme frekvensen som for vedprøver. B. mucronatus kolymensis og B. macromucronatus likner på B. xylophilus i generell biologi og habitatvalg. Hvis vi antar en hypotetisk frekvens i forekomsten til B. xylophilus som er 100 ganger lavere enn for disse naturlig forekommende nematodene, dvs. 0,00009, kan det antall prøver som trengs for en påvisning av B. xylophilus med 95 % konfidensintervall estimeres til 30 801. Dette indikerer at vi i dag hypotetisk sett har nådd bare 26 % av det antall prøver som trengs for å kunne erklære Norge fri for furuvednematoden B. xylophilus.
2019
Authors
Hugh Morris Ari Hietala Steven Jansen Javier Ribera Sabine Rosner Khalifah A. Salmeia Francis W. M. R. SchwarzeAbstract
No abstract has been registered
Authors
R. Ioos P. Chrétien J. Perrault C. Jeandel C. Dutech P. Gonthier F. Sillo Ari Hietala Halvor Solheim J. HubertAbstract
Four species of the destructive forest pathogen Heterobasidion annosum sensu lato (s.l.) are present in Europe: H. annosum sensu stricto (s.s.), H. abietinum and H. parviporum are native species, while H. irregulare is a non‐native invasive species currently reported only in Italy, yet recommended for regulation throughout Europe. In this study, real‐time PCR detection tests were developed for each of the four species, which can be used simultaneously or individually thanks to probes labelled with species‐specific fluorescent dyes. The different performance criteria of each assay were evaluated, and it was determined that they were theoretically capable of detecting amounts of DNA corresponding to 311, 29 and 29 cell nuclei in H. annosum s.s., H. irregulare and H. parviporum, respectively. The specificity of each assay was assessed with a wide set of strains. Real‐time PCR tests successfully detected Heterobasidion species from 36 fruiting bodies taken from the forest, as well as from artificially inoculated or naturally infected wood samples. The multiplex real‐time PCR assays developed in this study could have practical applications both in forest management and in phytosanitary monitoring.