Halvor Solheim

Seniorforsker (pensjonistavtale)

(+47) 920 33 663
halvor.solheim@nibio.no

Sted
Ås - Bygg H8

Besøksadresse
Høgskoleveien 8, 1433 Ås

Sammendrag

Hvert år importeres det store mengder av tømmer og treprodukter til Norge fra ulike land og verdensdeler. Uten tilstrekkelig årvåkenhet kan import av noen trevarer resultere i at det innføres fremmede arter av insekter, sopp, nematoder eller planter med svært uheldige virkninger i norske skoger. Import av tømmer og treprodukter kan dessuten i noen tilfeller medføre at Norge bidrar til handel med tømmer og treprodukter basert på tropiske treslag og hogst som på annen måte er ulovlig, og som kan bidra negativt for bærekraftig skogforvaltning og økonomi, fattigdomsreduksjon, beskyttelse av biomangfold og skogdekning for å redusere CO2-utslipp. Norge er del av tømmerforordningen som skal bidra til at import fra slik hogst ikke skal skje. I denne rapporten benytter vi tollstatistikk for å vurdere omfanget og variasjonen i import av tømmer og andre treprodukter som er relevant både for import av fremmede arter og for tømmerforordningen.

Sammendrag

European ash (Fraxinus excelsior), a keystone species with wide distribution and habitat range in Europe, is threatened at a continental scale by an invasive alien ascomycete, Hymenoscyphus fraxineus. In its native range of Asia, this fungus is a leaf endophyte with weak parasitic capacity and robust saprobic competence in local ash species that are closely related to European ash. In European ash, H. fraxineus has a similar functional role as in Asia, but the fungus also aggressively kills shoots, resulting in crown dieback and tree death. H. fraxineus is a typical invasive species, as its spread relies on high propagule pressure. While crown dieback of European ash is the most obvious symptom of ash dieback, the annual colonization of ash leaves is a crucial key dependency for the invasiveness of H. fraxineus, since its fruiting bodies are formed on overwintered leaf vein tissues in soil debris. Leaves of European ash host a wide range of indigenous epiphytes, endophytes, facultative parasites and biotrophic fungi, including Hymenoscyphus albidus, a relative of H. fraxineus that competes for the same sporulation niche as the invader. At face value, leaves of European ash are colonized by a large and diverse indigenous mycobiome. In order to understand why this invader became successful in Europe, we discuss and summarize the current knowledge of diversity, seasonal dynamics and traits of H. fraxineus and indigenous fungi associated with leaves of European ash.

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Ophiostoma spp. (Ophiostomatales, Ascomycota) are well-known fungi associated with bark and ambrosia beetles (Curculionidae: Scolytinae, Platypodinae). Fungi in the Ophiostomatales include serious tree pathogens as well as agents of timber blue-stain. Although these fungi have been extensively studied in the northern hemisphere, very little is known regarding their occurrence on hardwoods in Europe. The aims of the present study were to identify and characterize new Ophiostoma spp. associated with bark and ambrosia beetles infesting hardwoods in Norway and Poland, and to resolve phylogenetic relationships of Ophiostoma spp. related to the Norwegian and Polish isolates, using multigene phylogenetic analyses. Results obtained from five gene regions (ITS, LSU, b-tubulin, calmodulin, translation elongation factor 1-a) revealed four new Ophiostoma spp. These include Ophiostoma hylesinum sp. nov., O. signatum sp. nov., and O. villosum sp. nov. that phylogenetically are positioned within the Ophiostoma ulmi complex. The other new species, Ophiostoma pseudokarelicum sp. nov. reside along with Ophiostoma karelicum in a discrete, well-supported phylogenetic group in Ophiostoma s. stricto. The results of this study clearly show that the diversity and ecology of Ophiostoma spp. on hardwoods in Europe is poorly understood and that further studies are required to enrich our knowledge about these fungi.

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Kapping og beskjæring av tretopper langs kraftlinjer med sag fra helikopter reduserer risikoen for trefall på kraftlinja og kan være et kostnadseffektivt tiltak med få ulemper for skogeier. Topping eller kvisting med helikopter gir mindre sjanse for vindfall, toppbrekk og snøbøy, dels ved at trærne får mindre vindfang og mindre snølast, og dels ved at vektarmen som kraften virker på blir kortere.

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Sammendrag

Political action can reduce introductions of diseases caused by invasive forest pathogens (IPs) and public support is important for effective prevention. The public’s awareness of IP problems and the acceptability of policies aiming to combat these pathogens were surveyed in nine European countries (N = 3469). Although awareness of specific diseases (e.g., ash dieback) varied, problem awareness and policy acceptability were similar across countries. The public was positive towards policies for informational measures and stricter standards for plant production, but less positive towards restricting public access to protected areas. Multilevel models, including individual and country level variables, revealed that media exposure was positively associated with awareness of IP problems, and strengthened the link between problem awareness and policy acceptability. Results suggest that learning about IPs through the media and recognizing the associated problems increase policy acceptability. Overall, the study elaborates on the anthropogenic dimension of diseases caused by IPs.

Sammendrag

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

Sammendrag

Skogens helsetilstand påvirkes i stor grad av klima og værforhold, enten direkte ved tørke, frost og vind, eller indirekte ved at klimaet påvirker omfanget av soppsykdommer og insektangrep. Klimaendringene og den forventede økningen i klimarelaterte skogskader gir store utfordringer for forvaltningen av framtidas skogressurser. Det samme gjør invaderende skadegjørere, både allerede etablerte arter og nye som kan komme til Norge i nær framtid. Denne rapporten presenterer resultater fra skogskadeovervåkingen i Norge i 2017 og trender over tid for følgende temaer...

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Sammendrag

Accelerating international trade and climate change make pathogen spread an increasing concern. Hymenoscyphus fraxineus, the causal agent of ash dieback, is a fungal pathogen that has been moving across continents and hosts from Asian to European ash. Most European common ash trees (Fraxinus excelsior) are highly susceptible to H.fraxineus, although a minority (~5%) have partial resistance to dieback. Here, we assemble and annotate a H.fraxineus draft genome, which approaches chromosome scale. Pathogen genetic diversity across Europe and in Japan, reveals a strong bottleneck in Europe, though a signal of adaptive diversity remains in key host interaction genes. We find that the European population was founded by two divergent haploid individuals. Divergence between these haplotypes represents the ancestral polymorphism within a large source population. Subsequent introduction from this source would greatly increase adaptive potential of the pathogen. Thus, further introgression of H.fraxineus into Europe represents a potential threat and Europe-wide biological security measures are needed to manage this disease.

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Sammendrag

Species of Leptographium are characterized by mononematous or synnematous conidiophores and are commonly associated with different arthropods. Some of them also produce a sexual state characterised by globose ascomata with elongated necks. Compared to investigations on coniferous trees, the occurrence of Leptographium species on hardwood trees has been poorly studied in Europe. During a survey of ophiostomatoid fungi on various hardwood tree species in Norway and Poland, three unusual species, which fit in the broader morphological description of Leptographium spp., were found in association with Trypodendron domesticum, Trypodendron signatum and Dryocoetes alni, and from wounds on a variety of hardwoods. Phylogenetic analyses of sequence data for six different loci (ITS1–5.8 S–ITS2, ITS2-LSU, ACT, b-tubulin, CAL, and TEF-1a) showed that these Leptographium species are phylogenetically closely related to the species of the Grosmannia olivacea complex. The first species forms a well-supported lineage that includes Ophiostoma brevicolle, while the two other new taxa resided in a separate lineage; possibly affiliated with Grosmannia francke-grosmanniae. All the new species produce perithecia with necks terminating in ostiolar hyphae and orange-section shaped ascospores with cucullate, gelatinous sheaths. These species also produce dark olivaceous mononematous asexual states in culture. In addition, two of the newly described species have a second type of conidiophore with a short and non-pigmented stipe. The new Leptographium species can be easily distinguished from each other by their appearance and growth in culture. Based on novel morphological characters and distinct DNA sequences, these fungi were recognised as new taxa for which the names Leptographium tardum sp. nov., Leptographium vulnerum sp. nov., and Leptographium flavum sp. nov. are provided.

Sammendrag

In Norway the common ash (Fraxinus excelsior L.) has its northernmost distribution in Europe. It grows along the coastal range as small fragmented populations. The first occurrence of ash dieback caused by Hymenoscyphus fraxineus in Norway was reported in 2008. At that time, the disease had already spread through large areas of southern and south-eastern parts of Norway. Since then the disease continued spreading with a speed of about 50- 60 km per year along the western coastal range. To monitor the disease development over time, we established eight permanent monitoring plots in south-eastern and western Norway in 2009 and 2012, respectively. In all plots tree mortality was high, especially among the youngest trees in south-eastern Norway. The extent of crown damage has continually increased in all diameter classes for both regions. In 2009, 76.8 % of all trees on the five monitoring plots in south-eastern Norway were considered to be healthy or slightly damaged, and only 8.9 % to be severely damaged. In 2015, 51.7 % were dead, 13.5 % severely damaged and only 25.7 % remained healthy or slightly damaged. To assess the infection pressure and spore dispersal patterns of the pathogen, we used a Burkard volumetric spore sampler placed in an infested ash stand in southern Norway. We examined the airborne ascospores of H. fraxineus and H. albidus captured on the sampling tape microscopically and with real-time PCR assays specific to these fungi. We detected very few ascospores of H. albidus, whereas ascospores of H. fraxineus dominated throughout entire sampling periods of 2009, 2010 and 2011. Spore discharge occurred mainly between the hours of 5 and 8 a.m., though the distinctive sporulation had yearly variation between 5-7 a.m. We observed the same diurnal pattern throughout the entire sampling period, with a seasonal peak in spore liberation between mid-July and midAugust, after which the number of ascospores decreased substantially. Similar diurnal patterns were observed throughout the sampling period except that after mid-August the number of trapped ascospores substantially decreased. To compare the genetic pattern of common ash in the northern and central ranges of Europe we analyzed the Norwegian samples together with available samples from central Europe by using chloroplast and nuclear microsatellite markers. We found that the northern range of common ash was colonized via a single migration route that originated in eastern or south-eastern Europe with little influence originating from other southern or western European refugia. In the northern range margins, genetic diversity decreased and population differentiation increased, coherent with a post-glacial colonization history characterized by founder events and population fluctuations. Based on our findings we discuss the future management and conservational implications.

Sammendrag

Askeskuddsjuke forårsakes av en liten sopp, Hymenoscyphus fraxineus, på norsk kalt askeskuddbeger. Sjukdommen har i løpet av kort tid spredd seg over store deler av Europas askeskoger. Soppen er en fremmed art som trolig stammer fra Asia hvor den er assosiert med asketrær som er nær beslektet med europeisk ask. Det er særlig unge trær som er utsatt, men også eldre trær kan drepes over tid. Mye er uklart angående hvordan soppen infiserer, men sporene spres med vind til bladene på asketrær. Dersom soppen klarer å vokse forbi bladfestet før bladfall vil den i løpet av vinteren angripe greinene. Typiske symptomer er sår i barken og døde skudd.

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Sammendrag

Dieback of European ash (Fraxinus excelsior L.), a disease caused by the ascomycete Hymenoscyphus fraxineus (previously referred to as H. pseudoalbidus or Chalara fraxinea), was first observed in Poland in the early 1990ies, and is currently present almost throughout the entire distribution area of European ash. The characteristic symptoms of the disease include dead shoots with necrotic lesions in the bark and discoloration of xylem and pith but the seasonal dynamics of pathogen spread in shoot tissues remain poorly understood. To investigate whether the internal spread of the fungus involves season-specific patterns, saplings with necrotic bark lesions in 1-2 -year-old stem regions were collected during 2014-2015 at time intervals in spring, summer, autumn and winter at several localities in western Ukraine and at two localities in south-eastern Norway. Tissuespecific presence of H. fraxineus was determined by a highly sensitive quantitative real-time PCR assay that is specific to DNA of H. fraxineus. The relatively high proportion of bark samples positive for H. fraxineus in the saplings collected during spring provides support to a model that H. fraxineus can be a primary causative agent of bark lesions and that other fungi may eventually replace it in old infection areas.

Sammendrag

Ask er et av våre vanligste edellauvtrær og et viktig levested for mange arter. Ask er mye brukt som prydtre og har vært vanlig både som tuntre og i alleer. Gamle styvede asketrær representerer mange steder viktige kulturminner. Treslaget representerer derfor både en viktig natur- og kulturarv. Dessverre er ask hardt rammet av askeskuddsjuken, nesten overalt hvor asken vokser ser vi utbrudd. Dødeligheten er høg, og ask er oppført som sårbar på Norsk rødliste for arter. Denne veilederen gir deg informasjon om i) hvordan du kan kjenne igjen askeskuddsjuken, ii) viktigheten av å bevare friske trær, iii) hvordan du kan minske spredningen av askeskuddsjuken og iv) viktigheten av å bevare ask som art i edellauvskogen.

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Armillaria possesses several intriguing characteristics that have inspired wide interest in understanding phylogenetic relationships within and among species of this genus. Nuclear ribosomal DNA sequence– based analyses of Armillaria provide only limited information for phylogenetic studies among widely divergent taxa. More recent studies have shown that translation elongation factor 1-α (tef1) sequences are highly informative for phylogenetic analysis of Armillaria species within diverse global regions. This study used Neighbor-net and coalescence-based Bayesian analyses to examine phylogenetic relationships of newly determined and existing tef1 sequences derived from diverse Armillaria species from across the Northern Hemisphere, with Southern Hemisphere Armillaria species included for reference. Based on the Bayesian analysis of tef1 sequences, Armillaria species from the Northern Hemisphere are generally contained within the following four superclades, which are named according to the specific epithet of the most frequently cited species within the superclade: (i) Socialis/Tabescens (exannulate) superclade including Eurasian A. ectypa, North American A. socialis (A. tabescens), and Eurasian A. socialis (A. tabescens) clades; (ii) Mellea superclade including undescribed annulate North American Armillaria sp. (Mexico) and four separate clades of A. mellea (Europe and Iran, eastern Asia, and two groups from North America); (iii) Gallica superclade including Armillaria Nag E (Japan), multiple clades of A. gallica (Asia and Europe), A. calvescens (eastern North America), A. cepistipes (North America), A. altimontana (western USA), A. nabsnona (North America and Japan), and at least two A. gallica clades (North America); and (iv) Solidipes/Ostoyae superclade including two A. solidipes/ostoyae clades (North America), A. gemina (eastern USA), A. solidipes/ostoyae (Eurasia), A. cepistipes (Europe and Japan), A. sinapina (North America and Japan), and A. borealis (Eurasia) clade 2. Of note is that A. borealis (Eurasia) clade 1 appears basal to the Solidipes/Ostoyae and Gallica superclades. The Neighbor-net analysis showed similar phylogenetic relationships. This study further demonstrates the utility of tef1 for global phylogenetic studies of Armillaria species and provides critical insights into multiple taxonomic issues that warrant further study.

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The goal of this study was to assess the long-term effects of partial harvesting and supplementary soil scarification on the frequency of root and butt rot in managed uneven-sized Norway spruce stands. Frequency of rot and the population structure of the rot fungi were assessed on 1353 stumps after clear-cutting 21 years after a selection harvesting experiment. The initial experiment was comprised of three harvest strength (low, intermediate and high) of single-tree selection, removing approximately 25, 45 and 65% of the stand basal area. Uncut control plots were established at the same time. Supplementary soil scarification was applied in subplots within the single-tree selection plots, using a medium-sized excavator. After clear-cutting the stumps were analyzed with respect to rot caused by Heterobasidion parviporum, Armillaria spp., Stereum sanguinolentum as well as other rot fungi. Rot caused by Armillaria spp. was most common (8.6% of the stumps), while infection by H. parviporum (2.9%) or S. sanguinolentum (3.0%) was less frequent. The group “other rot” (5.4%) comprised 21 identified taxa, each occurring in 1–15 stumps. Significantly lower rot frequencies were found for the uncut control (16.3%) and intermediate harvest strength (15.7%), compared with low harvest strength (23.6%). A rot frequency of 21.0% was found in the high harvest strength. In two of three harvest strengths, the rot frequency was higher than for the uncut control. As the observed rot frequencies did not increase consistently with increasing harvest strength, the results do not completely support the initial expectations of increased rot after single-tree selection compared with the uncut control. However, since the probability of rot in individual stumps on plots treated with single-tree selection was significantly affected by the distance to the nearest strip road (H. parviporum) as well as dependent on the size of and distance to the nearest stump of trees cut during the experimental harvest (H. parviporum, S. sanguinolentum and total rot), it is evident that the single-tree selection harvesting was partially responsible for some of the observed rot. One of the selection criteria in the initial harvest was a sanitary removal of trees of poor vitality. Varying degrees of sanitation felling may therefore have offset the effects of new infections in wounds or spread of rot fungi through adjacent stumps. Supplementary soil scarification in small gaps of the residual stand had no significant effect on the frequency of rot, suggesting that such treatment may be used to facilitate regeneration in uneven-sized spruce stands on similar sites.

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Dothistroma septosporum, a notorious pine needle pathogen with an unknown historical geographic origin and poorly known distribution pathways, is nowadays found almost in all areas inhabited by pines (Pinus spp.). The main aim of this study was to determine the relationship between North European and East Asian populations. In total, 238 Eurasian D. septosporum isolates from 11 countries, including 211 isolates from northern Europe, 16 isolates from Russian Far East and 11 isolates from Bhutan were analysed using 11 species-specific microsatellite and mating type markers. The most diverse populations were found in northern Europe, including the Baltic countries, Finland and European Russia. Notably, D. septosporum has not caused heavy damage to P. sylvestris in northern Europe, which may suggest a long co-existence of the host and the pathogen. No indication was obtained that the Russian Far East or Bhutan could be the indigenous area of D. septosporum, as the genetic diversity of the fungus there was low and evidence suggests gene flow from northern Europe to Russian Far East. On the western coast of Norway, a unique genetic pattern was observed, which differed from haplotypes dominating other Fennoscandian populations. As an agent of dothistroma needle blight, only D. septosporum was documented in northern Europe and Asia, while D. pini was found in Ukraine and Serbia.

Sammendrag

Ash dieback, caused by the ascomycete Hymenoscyphus fraxineus, has been spreading throughout Europe since the early 1990s, threatening European ash at a continental scale. Little is known about the development of the disease in individual forest trees and in different age classes. In this study we monitored ash dieback on trees of different diameter classes in five permanent plots in ash stands in south-eastern Norway from 2009 to 2016, and from 2012 to 2016 in three plots in western Norway with a shorter disease history. Our results showed that more than 80% of the youngest and more than 40% of the intermediate future crop trees in the plots in south-eastern Norway were dead by 2016, while the disease development in large, dominant trees was slower. Although less damage has been observed in the plots in western Norway, the trend for the juvenile trees is the same as in south-eastern Norway with rapidly increasing damage and mortality. Most dead trees in south-eastern Norway were found at sites with high soil moisture and showed symptoms of root-rot caused by Armillaria species. Infected trees, both young and old ones, are weakened by the disease and appear to be more susceptible to other, secondary pathogens, especially under unfavourable site conditions.

Sammendrag

Fokus i denne rapporten er på skogbehandlingen, og på maksimering av verdiproduksjon. En forutsetning for dette er høy sagtømmerproduksjon, samtidig som det er viktig å vurdere arealets totale tømmerverdi. Følgende forutsetninger ligger til grunn for rapporten: Bevaring av biologisk mangfold og ivaretakelse av andre flerbrukshensyn Det legges til grunn at all skogbehandling utføres i henhold til dagens lovverk og frivillige sertifiseringsordninger, og at dette ivaretar hensyn til biologisk mangfold og andre flerbrukshensyn. Vi går derfor ikke inn på betydningen ulik skogbehandling vil ha for biologisk mangfold eller andre flerbrukshensyn, eller tilpasninger av skogbehandlingen for dette. Bærekraftig skogbruk i klimasammenheng Miljødirektoratet mfl. (2016) drøfter vern eller bruk av skog som klimatiltak. I rapporten konkluderes det med at det ikke er grunnlag for å vektlegge vern av norsk skog som klimatiltak. En forutsetning er at det drives et bærekraftig skogbruk i klimasammenheng. Dette ble definert som følger: «Bærekraftig skogbruk i klimasammenheng innebærer at skogens produktivitet og evne til å lagre karbon ikke forringes, og at karbonbeholdninger ikke reduseres permanent.» (Miljødirektoratet mfl. 2016). Vi forutsetter gjennom rapporten at skogbehandling drives bærekraftig i tråd med denne definisjonen, uten at vi går nærmere inn på betydningen og eventuelle nødvendige tilpasninger. Skogbehandling for å motvirke klimaendringer Skogbehandling som motvirker klimaendringer, for eksempel ved å øke karbonopptaket, vil i mange tilfeller være i samsvar med skogbehandling for maksimal verdiproduksjon, men ikke alltid. Vi har i denne rapporten kun fokusert på verdiproduksjon, og betydning av skogbehandling på ulike karbonbeholdninger er ikke vurdert. Driftstekniske forhold («hvordan ta ut tømmeret») Driftskostnader vil være av stor betydning for skogeiers økonomiske resultat, og både de endringer vi allerede ser og forventede klimaendringer er forventet å gi større driftstekniske utfordringer. I denne rapporten ser vi imidlertid utelukkende på den betydning skogbehandlingen vil ha for antatt verdiproduksjon.

Sammendrag

Den årlige skogovervåkingen viser at granas kronetilstand har bedret seg betraktelig på Vestlandet og i Midt-Norge etter de omfattende frosttørkeskadene der i 2013 og 2014. Furu hadde generelt lite skader. Det var mer skader på bjørk i 2016 enn i 2015, og både måler- og bjørkerustangrep økte i frekvens, men også abiotiske faktorer hadde stor betydning for bjørkas helsetilstand. Skadeomfanget var størst i Nord-Norge, der særlig gjentatte målerangrep over mange år utgjør et problem for bjørkeskogen. Askeskuddsjuke har i løpet av drøyt 10 år spredt seg gradvis gjennom mesteparten av askas utbredelsesområde i Norge. Overvåkingen viser at skadeutviklingen skjer fort, og særlig de yngste trærne har høy mortalitet. I Nord-Trøndelag og Oppland ble det registrert en økning i fangstverdiene av granbarkbiller i 2017, mens de øvrige fylkene opplevde en liten til moderat nedgang, mye på grunn av en kjølig og nedbørrik sommer.

Sammendrag

Skogens helsetilstand påvirkes i stor grad av klima og værforhold, enten direkte ved tørke, frost og vind, eller indirekte ved at klimaet påvirker omfanget av soppsykdommer og insektangrep. Klimaendringene og den forventede økningen i klimarelaterte skogskader gir store utfordringer for forvaltningen av framtidas skogressurser. Det samme gjør invaderende skadegjørere, både allerede etablerte arter og nye som kan komme til Norge som følge av økt handel og import. Eksempler på begge er omtalt i denne rapporten som presenterer resultater fra skogskadeovervåkingen i Norge i 2016........

Sammendrag

Ash dieback, caused by the ascomycete Hymenoscyphus fraxineus, was first observed in the eastern and southernmost Norway in 2008. Based on the age of stem bark lesions, it was concluded that the fungus had arrived to the region no later than 2006. Since 2008 the annual spread of the disease northwards along the west coast of Norway has been monitored. The registration was done each year during early summer around a disease frontier recorded in the previous year. The occurrence of necrotic bark lesions in the previous-year shoots and dieback of these shoots, and isolation of H. fraxineus from the discoloured wood associated with necrotic bark lesions were used as signs of ash dieback. These records indicate an annual spread of ash dieback in the range between 25 km and 78 km, and a mean annual spread of 51 km. The cause of the spread is discussed.

Sammendrag

Askeskuddsjuke har spredd seg med rekordfart i Europa og i Norge. Ask (Fraxinus excelsior) er meget sensitiv for denne nye sjukdommen. De aller fleste områder i Europa med dette treslaget er nå infisert med sekksporesoppen askeskuddbeger (Hymenoscyphus fraxineus) som forårsaker sjukdommen. I Norge ble askeskuddsjuke første gang registrert i 2008 og allerede da ble den funnet over store deler av Østlandet og Sørlandet. Deretter har askeskuddsjuke spredd seg nordover på Vestlandet i gjennomsnitt 51 km per år. I 2016 ble det nordligste funnet registrert i Aure kommune nær grensa til Trøndelag.

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Species of Leptographium are generally characterized by mononematous conidiophores and are commonly associated with bark beetles and weevils. These species are responsible for sapstain and in some cases serious diseases on a range of primarily coniferous trees. In comparison with coniferous trees, the occurrence of Leptographium species on hardwood trees has been poorly studied in Europe. During a survey of ophiostomatoid fungi on various tree species in Norway and Poland, three unusual species, which fit the broader morphological description of Leptographium spp., were found in association with Scolytus ratzeburgi, Dryocoetes alni and Trypodendron domesticum on a variety of hardwoods, and from wounds on Tilia cordata. Phylogenetic analyses of sequence data for three gene regions (ITS2-LSU, β-tubulin, and TEF1-α) showed that these Leptographium species are phylogenetically closely related to each other and form a well-supported lineage that included Grosmannia grandifoliae and Leptographium pruni. The first species could be distinguished from the other Leptographium species based on conidiophores arising from spiral hyphae, chlamydospore-like structures and a hyalorhinocladiella-like synanamorph in culture. The second species differs from the previous one by having distinctly shorter conidiophores and smaller conidia. This species also produces a well-developed sporothrix-like synanamorph with denticulate conidiogenous cells. Based on these unusual morphological characteristics and distinct DNA sequences, these fungi were recognised as new taxa for which the names Leptographium trypodendri sp. nov. and L. betulae sp. nov. are provided. The third group of isolates belonged to Grosmannia grandifoliae, representing the first report of this species outside of the USA. The newly defined G. grandifoliae complex is the first species complex in Leptographium s.l. consisting of only hardwood-infecting species.

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High biodiversity is regarded as a barrier against biological invasions. We hypothesized that the invasion success of the pathogenic ascomycete Hymenoscyphus fraxineus threatening common ash in Europe relates to differences in dispersal and colonization success between the invader and the diverse native competitors. Ash leaf mycobiome was monitored by high-throughput sequencing of the fungal internal transcribed spacer region (ITS) and quantitative PCR profiling of H. fraxineus DNA. Initiation of ascospore production by H. fraxineus after overwintering was followed by pathogen accumulation in asymptomatic leaves. The induction of necrotic leaf lesions coincided with escalation of H. fraxineus DNA levels and changes in proportion of biotrophs, followed by an increase of ubiquitous endophytes with pathogenic potential. H. fraxineus uses high propagule pressure to establish in leaves as quiescent thalli that switch to pathogenic mode once these thalli reach a certain threshold – the massive feedback from the saprophytic phase enables this fungus to challenge host defenses and the resident competitors in mid-season when their density in host tissues is still low. Despite the general correspondence between the ITS-1 and ITS-2 datasets, marker biases were observed, which suggests that multiple barcodes provide better overall representation of mycobiomes.

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The root rot pathogens in Norway spruce (Picea abies) Heterobasidion ssp. cause substantial loss in carbon sequestered in forest and economic revenue for forest owners. To facilitate strategic breeding planning for increased resistance against this pathogen in particular, the blue stain fungus Endoconidiophora polonica, growth and wood quality traits (wood density and spiral grain), we estimated additive genetic parameters, correlations and the potential response from selection. Parameters were estimated from a progeny trial series established at two sites (25 years from planting) and their parents in a seed orchard (43 years from grafting). A standard half-sib analysis based on progenies and a parent–offspring regression was used for estimation of heritabilities. Resistance against the pathogens was measured as lesion length under bark after inoculations in phloem. Heritability values varied with site and estimation procedure from 0.06 to 0.33, whereas the phenotypic variance (as CV P ) is high and fairly stable around 40–50 %. Heritability values for wood density and spiral grain in the same material varied from 0.32 to 0.63. The highest heritability values were generally obtained from parent–offspring regression. There is no evidence of resistance traits being genetically correlated with growth or wood quality traits. Wood density is negatively correlated with stem diameter. Implications for breeding are discussed.

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Dothistroma needle blight (DNB) is one of the most important diseases of pine. Although its notoriety stems from Southern Hemisphere epidemics in Pinus radiata plantations, the disease has increased in prevalence and severity in areas of the Northern Hemisphere, including Europe, during the last two decades. This increase has largely been attributed to expanded planting of susceptible hosts, anthropogenic dispersal of the causative pathogens and changes in climate conducive to disease development. The last comprehensive review of DNB was published in 2004, with updates on geographic distribution and host species in 2009. Importantly, the recognition that two species, Dothistroma septosporum and D. pini, cause DNB emerged only relatively recently in 2004. These two species are morphologically very similar, and DNA-based techniques are needed to distinguish between them. Consequently, many records of host species affected or geographic location of DNB prior to 2004 are inconclusive or even misleading. The objectives of this review were (i) to provide a new database in which detailed records of DNB from 62 countries are collated; (ii) to chart the current global distribution of D. septosporum and D. pini; (iii) to list all known host species and to consider their susceptibility globally; (iv) to collate the published results of provenance trials; and (v) to consider the effects of site factors on disease incidence and severity. The review shows that DNB occurs in 76 countries, with D. septosporum confirmed to occur in 44 and D. pini in 13. There are now 109 documented Pinaceae host taxa for Dothistroma species, spanning six genera (Abies, Cedrus, Larix, Picea, Pinus and Pseudotsuga), with Pinus being the dominant host genus, accounting for 95 host taxa. The relative susceptibilities of these hosts to Dothistroma species are reported, providing a resource to inform species choice in forest planting. Country records show that most DNB outbreaks in Europe occur on Pinus nigra and its subspecies. It is anticipated that the collaborative work described in this review will both underpin a broader global research strategy to manage DNB in the future and provide a model for the study of other forest pathogens.

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Dieback of European ash was first observed in Europe in the early 1990s. The disease is caused by the invasive ascomycete Hymenoscyphus fraxineus, proposed to originate from Far East Asia, where it has been considered a harmless saprotroph. This study investigates the occurrence of H. fraxineus in tissues of local ash species in the Russian Far East, and assesses its population-specific genetic variation by ITS sequencing. Shoot dieback symptoms, characteristic of H. fraxineus infection on European ash, were common, but not abundant, on Fraxinus mandshurica and Fraxinus rhynchophylla trees in Far East Russia. High levels of pathogen DNA were associated with necrotic leaf tissues of these ash species, indicating that the local H. fraxineus population is pathogenic to their leaves. However, the low levels of H. fraxineus DNA detected in shoots with symptoms, the failure to isolate this fungus from such tissues, and the presence of other fungi with pathogenic potential in shoots with symptoms indicate that local H. fraxineus strains may not be responsible (or their role is negligible) for the observed ash shoot dieback symptoms in the region. Conspicuous differences in ITS rDNA sequences detected between H. fraxineus isolates from Russian Far East and European populations suggest that the current ash dieback epidemic in Europe might not directly originate from the Russian Far East. Revision of the herbarium material shows that the earliest specimen of H. fraxineus was collected in 1962 from the Russian Far East and the oldest H. fraxineus specimen of China was collected in 2004.

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Råte påfører norske skogeiere og skogbruket årlige tap estimert til rundt 100 mill. NOK (Solheim og Stamnes, upubl.). Basert på den siste nasjonale råteundersøkelsen i granskog (Huse m.fl. 1994), var det mest råte i granas naturlige utbredelsesområde (Aust-Agder, Østlandet og Midt-Norge opp til Saltfjellet), hvor i gjennomsnitt nesten hvert fjerde tre var råteinfisert ved slutthogst. I enkelte granbestand kan råtefrekvensen ved slutthogst komme opp mot 60- 70 %. I skogreisingsstrøk (Vest-Agder, Vestlandet og Nord-Norge nord for Saltfjellet) var bare opptil hvert tiende hogstmodent grantre råteinfisert. I 2014 ble det utført en liten spørreundersøkelse for å kartlegge hvor bevisste de forskjellige aktørene i skogbruket er på råteproblemet, om de mener problemet har endret seg de senere årene og i hvilken grad det brukes forebyggende kontrolltiltak mot råte.

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Skogens helsetilstand påvirkes i stor grad av klima og værforhold, enten direkte ved tørke, frost og vind, eller indirekte ved at klimaet påvirker omfanget av soppsykdommer og insektangrep. Klimaendringene og den forventede økningen i klimarelaterte skogskader gir store utfordringer for forvaltningen av framtidas skogressurser. Det samme gjør invaderende skadegjørere, både allerede etablerte arter og nye som kan komme til Norge i framtida. Eksempler på begge er omtalt i foreliggende rapport. I denne rapporten presenteres resultater fra skogskadeovervåkingen i Norge i 2015: (i) Overvåking av skogens helsetilstand på de landsrepresentative flatene. (ii) Skogøkologiske analyser og målinger av luftkjemi på de intensive overvåkingsflatene. (iii) Barkbilleovervåking og analyse av klimaeffekter. (iv) Import skadegjørere og analyse av invasjonspotensialet til fremmede billearter. (v) Overvåking av askeskuddsyke. (vi) Andre skaderegistreringer fra Skogskader.no og befaringer i 2015. Skogovervåkingen på de landsrepresentative flater viser at gran- og furuskogens generelle helsetilstand var god i 2015, selv om det ble registrert uvanlig mange skader på gran og kronetettheten hos furu hadde sunket i forhold til året før. Siden 2007 har kronetettheten likevel økt hos begge treslagene mens trenden har vært motsatt i ICP Forests’ nettverk. Det var lite misfarging på gran og furu og få skader på furu i 2015, mens bjørk, som tidligere, hadde flest skader av alle undersøkte treslag. Det ble ellers registrert få spesielle skader på skog i 2015. Konsentrasjon og atmosfærisk avsetning av både svovel og nitrogen var generelt veldig lave i 2015. Konsentrasjonen av uorganiske nitrogenforbindelser i jordvann og nivået av bakkenært ozon var også lave i Norge i 2015. Ozonnivåene er i stor grad styrt av værforholdene og vil derfor kunne oppvise store årlige variasjoner. Kjemiske analyser på de intensive skogovervåkings-flatene i Norge har dokumentert en betydelig reduksjon over tid i nivåer av svovelkomponenter både i luft, nedbør og jordvann som følge av store utslippsreduksjoner i Europa. Overvåkingsflata på Sørlandet, som er mest utsatt for langtransporterte forurensinger, hadde som i tidligere år de høyeste nitrogen- og svovelverdier i barnålene i 2015. Verdiene hadde økt i forhold til 2013 og var på det høyeste nivået siden hhv. 1995 og 1999, til tross for at både tilførselen og deposisjonen av disse elementene har avtatt sterkt siden 1990. På de to andre flatene var nitrogenverdiene vesentlig lavere, og i Osen var det dessuten for lite nitrogen i forhold til de andre næringsstoffene. Nitrogenmangel er imidlertid normalt i boreale barskoger. Vegetasjonsanalyser på den intensive skogovervåkingsflata i Hurdal viser at dekningen av etasjehusmose og to vmoser har økt siden 1999, mens flere andr mosearter har gått tilbake. Økt vekst av store bladmoser som etasjehusmose er også dokumentert av andre norske studier og har blitt forklart som et resultat av at mange milde og nedbørrike høster har gjort vekstsesongen lengre. Resultatene fra granbarkbilleovervåkingen i 2015 viste en moderat økning av populasjonene for landet sett under ett. Analyser av tidsserier for klimaeffekter og utviklingen i granbarkbillebestanden indikerer en trend mot økende barkbillemengder i Trøndelag og Nordland, som har mye hogstmoden gran. Denne økningen er mest markert i tørre og varme år. Tidligere modellberegninger har predikert at den forventete temperaturøkningen kan føre til at granbarkbillen får to generasjoner per sommer i stedet for én så langt nord som Trøndelag, noe som kan gi en markert økning i antall angrep på stående trær...

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Two species of blue-stain fungi with similar morphologies, Ophiostoma brunneo-ciliatum and Ophiostoma 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-1α 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, Ophiostoma brunneolum, Ophiostoma macroclavatum and Ophiostoma pseudocatenulatum, are described in the newly defined O. clavatum-complex. The other two species included in the complex are Ophiostoma ainoae and Ophiostoma 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.

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Globally, billions of tons of carbon sequestered in trees are annually recycled back to the atmosphere through wood decomposition by microbes. In Norway, every fifth Norway spruce shows at final harvest infection by pathogenic white-rot fungi in the genera Heterobasidion and Armillaria. As these fungi can mineralize all components of wood, we predicted that they have a significant carbon footprint. Gas samples taken from infected stems were analyzed for CO2 and CH4 concentrations, and wood samples from different parts of the decay columns were incubated under hypoxic (4% O2) and anoxic laboratory conditions. In spring and summer the stem concentrations of CO2 were generally two times higher in trees with heartwood decay than in healthy trees. For most of the healthy trees and trees with heartwood decay, mean stem concentrations of CH4 were comparable to ambient air, and only some Armillaria infected trees showed moderately elevated CH4. Consistently, low CH4 production potentials were recorded in the laboratory experiment. Up-scaling of CO2 efflux due to wood decay in living trees suggests that the balance between carbon sequestration and emission may be substantially influenced in stands with high frequency of advanced root and stem heartwood decay.

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Ten saplings of European ash (Fraxinus excelsior L.) naturally infected by the invasive ash dieback pathogen Hymenoscyphus fraxineus were collected in Ukraine and Norway and examined for bark necrosis and extension of discoloration in sapwood and pith in a stem region. Tissue-specific colonization profiles were determined by spatial analyses of symptomatic and visually healthy stem tissues using a H. fraxineus-specific qPCR assay and light microscopy. Our data suggest that hyphal growth in the starch-rich perimedullary pith is of particular importance for both axial and radial spread of H. fraxineus, but that most of its biomass accumulates in sapwood parenchyma. The study confirms the results from earlier work and presents new information that refines the current stem invasion model.

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Fortellingen om høstens farger kan få selv realfagsinker til å se skjønnheten i de kjemiske og biologiske prosessene. Hør bare: Grønt klorofyll, gule karotenoider og røde antocyaniner er alle fargestoffer som hjelper plantene å fange sollyset.

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Ari M. Hietala, Volkmar Timmermann, Isabella Børja & Halvor Solheim Norwegian Forest and Landscape Institute. PO Box 115, 1431 Ås, Norway: ari.hietala@skogoglandskap.no Owing to the Gulf Stream, the northernmost European populations of several tree species are found in Norway. Common ash (Fraxinus excelsior), the only native ash species in Norway, is present in the lowlands in the southeastern part with continental climate and in southern and southwestern coastal regions with North Atlantic climate up to Central Norway. The current standing volume of ash in Norway is ca 3 mill m3 (broadleaved trees in total 220 mill m3). The first documentation of Ash Dieback (ADB) is from 2008 from a nursery in the southeastern part of the country. A survey later that year showed that dieback symptoms were present over a distance of nearly 400 km in the southeastern region. In addition to nurseries and forests, ADB symptoms were observed on roadside, alley, garden and park trees. Based on the presence of old ADB-like stem lesions detected in 2008, the pathogen must have arrived to Norway no later than 2006. In 2008, the Norwegian Food Safety Authority laid down regulations with the aim of preventing further spread of ADB. These regulations divide the country into quarantine, observation and infection-free zones, and prohibit the export of ash seedlings, seed and wood from the quarantine zone. Despite of these regulations, the disease spread rapidly along the western coast in the period between 2009 and 2013, and currently only the ash stands in Central Norway are free of the disease. The rapid spread of the disease in Norway is obviously due to airborne dispersal of pathogen ascospores. In our experimental stand in SE Norway the number of pathogen fruit bodies can be as high as 10,000 per m2 in the peak season, mid-July to mid-August. During the early morning hours the amount of pathogen ascospores at a diseased stand can exceed 100,000 ascospores per m3 air. The first symptoms of the disease, necrotic lesions on leaf blade and petiole, appear typically during the first two weeks of August in SE Norway. To observe long-term impacts of ADB, eight monitoring plots have been established in continental and North Atlantic climate zones. In SE Norway with the oldest disease history, above 60 % of the trees with a breast height diameter (BHD) below 12.5 cm have so far died or suffer from severe defoliation, 1/3 of the larger trees being affected to a similar degree. The proportions of healthy (no signs of defoliation) small and larger trees are 20% and 37%, respectively. In SW Norway with more recent disease history a similar trend is observed but the proportion of dead trees is still small. As a consequence of ADB, the Norwegian nurseries no longer grow ash seedlings. There are currently no practical control options for the disease in forestland. Several European countries have reported that even at heavily diseased ash stands there are often some ash trees that show little symptoms. This may be due to genetic variation between trees in disease resistance, a hypothesis that is currently being investigated in several European projects. Thus implementation of forest management practices that eliminate ash could have a negative effect as survival of the tree ultimately depends on selection of trees with increased disease resistance. Bibliography for Ari M. Hietala Ari M. Hietala is a Senior Forest Pathologist at the Norwegian Forest and Landscape Institute, which is a primarily government funded organisation providing scientific research and services to government, non-governmental and commercial organisations. He has worked with a range of fungal root and shoot diseases occurring on broadleaved trees and conifers indigenous to the Nordic countries. Ari and the rest of the group participate currently in several European consortia engaged in ash dieback research.

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Satellittdata har et potensial til å bidra til å dekke viktige kartleggings- og overvåkingsoppgaver i skog, særlig for deteksjon av skogskader og hogst. Formålet med prosjektet er å utvikle og demonstrere metoder for en operativ overvåkingstjeneste for stormskader og hogst. I tillegg skal det undersøkes om det er mulig å detektere og overvåke askeskuddsyke, som vil være særlig vanskelig. En test av mulighetene for dette er gjort på utvalgte tilfeller av hogst og stormskader i Norge, i tillegg til et område skadd av askeskuddsyken. Resultatene viste at • Stormskader i skog kan bare til en viss grad detekteres tilfredsstillende og innen rimelig tid (2 uker) med Landsat eller Sentinel-2. Det vil fungere i de tilfellene der o skadene er sterke, dvs tilnærmet alle trær er blåst ned, og o skadeområdet dekker et areal av en viss størrelse (minimum 10 daa), o skadene skjer utenfor mørketida om vinteren, og o det ikke er vedvarende skydekke. • Snauhogst kan detekteres tilfredsstillende med Landsat eller Sentinel-2. For dette formålet trenger man ikke en rask deteksjon, og det er uproblematisk å vente til sky- og lysforhold er tilfredsstillende. • Stormskader og hogst kan detekteres tilfredsstillende med Tandem-X, dersom man har en høydemodell fra før stormen. • Askeskuddsyke kan ikke detekteres med satellitt, fordi skadene i begynnelsen ofte er svake, de utvikler seg langsomt og de varierer mye fra tre til tre. • Automatisk prosessering av satellittbilder, og direkte overføring av resultatene over Internett for visning i Skog og landskaps Kilden krever noe systemutvikling, men er ikke problematisk dersom det er basert på åpne verktøy (Open source).

Sammendrag

Almesyke går på flere almearter og har nesten utradert alm fra store deler av Europa og Nord- Amerika. Til tross for at vanlig alm (Ulmus glabra) er særdeles mottakelig for almesyke, har den en begrenset utbredelse og betydning i Norge. Almesykesopp spres primært ved hjelp av almesplintborere i slekta Scolytus. I Norge har vi bare en art av almesplintborere og den er ikke så effektiv til å spre sykdommen. Klimaendringer vil trolig føre til at almesplintborere som er mer effektive til å overføre sykdommen, etablerer seg i Norge, noe som vil øke skadeomfanget betraktelig.

Sammendrag

Bjørkerust er vanlig i hele landet hvor vi har bjørk. Hvert år kan en finne angrepne bjørketrær, men enkelte år er soppangrepene store og omfattende. En fuktig forsommer i kombinasjon med en fuktig og varm ettersommer er avgjørende for store angrep. De siste 20 årene har det i varierende grad blitt observert store angrep. Om dette skyldes tilfeldige variasjoner eller klimaendringer er usikkert.

Sammendrag

Einertørke, forårsaket av Stigmina juniperina, ble første gang registrert i Norge i 2012. Det ble gjort funn av soppen mange steder i Sør-Norge. Om den er ny i Norge i dette århundre, eller om den har en oppblomstring grunnet klimaendringer er vanskelig å si nå, men soppen har hatt en oppblomstring både i Finland og Sverige.

Sammendrag

I vårt langstrakte land langt mot nord er frost en viktig faktor og årsak til mye skogskader. Nå i vår er blåbærlyng brun mange steder på Østlandet, men også grana har fått frostskader. I tillegg er det en del angrep av granrustsoppen, og i granbestand kan frostskader og granrust opptre i samme bestand.

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Furuas knopp- og grentørkesopp er en av furuskogens verste skadegjørere, og forårsaker år om annet store tap. Det største angrepet skjedde i 2001 hvor enorme områder i Sør-Norge og Sør-Sverige ble berørt. Milde høster og ustabile vintre kan føre til flere slike angrep.

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Furuskytte har lenge vært kjent som en skadegjører i planteskoler. Lenger sør i Europa har furuskytte vært regnet som en av de viktigste skadegjørerne i furuforyngelser. De senere årene er det også registrert mye skade på furuforyngelse i de sørlige deler av Norge med et toppår i 2001. Mildvær med mye fuktighet på ettersommeren og høsten gir soppen gode betingelser for infeksjoner.

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The pathogenic white-rot basidiomycete Heterobasidion irregulare is able to remove lignin and hemicellulose prior to cellulose during the colonization of root and stem xylem of conifer and broadleaf trees. We identified and followed the regulation of expression of genes belonging to families encoding ligninolytic enzymes. In comparison with typical white-rot fungi, the H. irregulare genome has exclusively the short-manganese peroxidase type encoding genes (6 short-MnPs) and thereby a slight contraction in the pool of class II heme-containing peroxidases, but an expansion of the MCO laccases with 17 gene models. Furthermore, the genome shows a versatile set of other oxidoreductase genes putatively involved in lignin oxidation and conversion, including 5 glyoxal oxidases, 19 quinone-oxidoreductases and 12 aryl-alcohol oxidases. Their genetic multiplicity and gene-specific regulation patterns on cultures based on defined lignin, cellulose or Norway spruce lignocellulose substrates suggest divergent specificities and physiological roles for these enzymes. While the short-MnP encoding genes showed similar transcript levels upon fungal growth on heartwood and reaction zone (RZ), a xylem defense tissue rich in phenolic compounds unique to trees, a subset of laccases showed higher gene expression in the RZ cultures. In contrast, other oxidoreductases depending on initial MnP activity showed generally lower transcript levels on RZ than on heartwood. These data suggest that the rate of fungal oxidative conversion of xylem lignin differs between spruce RZ and heartwood. It is conceivable that in RZ part of the oxidoreductase activities of laccases are related to the detoxification of phenolic compounds involved in host-defense. Expression of the several short-MnP enzymes indicated an important role for these enzymes in effective delignification of wood by H. irregulare.

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Granrustsoppen angriper unge nåler. Sterke og gjentagende angrep kan gi tilveksttap. Størst skade gjør imidlertid soppen i juletreplantasjer. Fuktige forhold i infeksjonsfasen er viktig. I de siste 20 årene har det i varierende grad vært observert sterke angrep. Om det er klimaendringer eller bare tilfeldige variasjoner som er årsaken er usikkert.

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Vi har flere arter av honningsopp i Norge, og to av dem, skog- og hagehonningsopp, er svært aktive ute i skogen. Begge artene forårsaker innråte i trær, men kan også opptre mer aggressivt og drepe svekkede trær nokså raskt. Honningsopp er involvert i grantørke som i de senere årene har utviklet seg til det verre, trolig i takt med klimaendringer.

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l år har eineren blitt utsatt for vinterskader over store deler av landet. Mer bekymringsfullt er den økende einertørken som har pågått noen få år nå. Årsaken er en sopp, Passalora juniperina, som ble registrert for første gang i Norge i 2012. Fram til nå er denne soppen funnet mange steder i Sør-Norge. Om den er ny i Norge, eller om den nå har en oppblomstring på grunn av klimaendringer er vanskelig å si.

Sammendrag

Mange sopper har sporer som kan spres over lange avstander og dermed være blant organismene som raskt kan etablere seg på nye steder om klimaet tillater det. Det er derfor mange sopparter blant klimavinnerne. De kan plasseres i forskjellige kategorier alt etter deres levested i dag og hvilken skade de gjør. Adoptert fra en serie om klimavinnere blant insekter i Norsk Skogbruk i 2009 med bidrag hovedsakelig fra seniorforskerne Paal Krokene og Bjørn Økland, kan den samme inndelingen også brukes på de patogene soppene.

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”Klimavinnerne” var tittelen på en artikkelserie i Norsk Skogbruk i 2012 der det ble gitt eksempler på sopper som ville kunne dra nytte av et varmere og våtere klima i Norge. Artiklene fokuserte på arter som opptrer som skadegjørere i skog. Problemene som disse soppene kan gi for det profesjonelle skogbruket, for hageeiere og den alminnelige turgåer, ble belyst. Forfatterne er alle forskere ved Norsk institutt for skog og landskap og har i en årrekke arbeidet med disse problemstillingene. De er Norges ledende innenfor dette fagfeltet. Seniorforsker Halvor Solheim tok initiativet til serien, og er seriens faglige redaktør. Vi er takknemlige for at Norsk Skogbruk trykket disse artiklene, og vi er også glad for at redaksjonen tillot oss å lage dette opptrykket som vi håper at mange vil ha nytte av.

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Common juniper (Juniperus communis) hosts not many pests or pathogens, but recently increasing needle blight has been observed in Norway. During a survey the needle blight was recorded in many parts of southern Norway but not above 550 m a.s.l., and it has been found both in forests, pastures and gardens. Trees are affected differently; some trees seem to be unaffected, while other trees may be killed. The cause of the disease is a fungus in the family Mycosphaerellaceae hitherto not reported from Norway. In forest pathology literature it has been named Stigmina juniperina, but also Asperisporium juniperinum. However, based on results of molecular sequence analyses it is proposed here that a more appropriate name should be Passalora juniperina (Georgescu & Badea) H. Solheim comb. Nov.

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Phytophthora-arter, er aggressive, sopp-lignende skadegjørere, som fremmes av fuktig og mildt klima. I Norge er flere arter oppdaget på trær i parker eller skogholt nær hager. Varslede klimaendringer, med økt temperatur og nedbør, kan skape gode vekstforhold slik at flere arter kan etablere seg også i skogområder.

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Det er ikke registrert sammendrag

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Vi har to arter av rotkjuke i Norge, gran- og fururotkjuke. Som navnet sier så har de hvert sitt treslag som hovedvert, men begge kan gå på andre treslag, også løvtrær. Soppens spesielle biologi gjør at en kan forvente økende råteproblemer grunnet klimaendringer. Mer stormaktivitet gir mer rotrykking og lettere tilgang for rotkjuke, mens mildere klima med lengre vekstsesong gjør at perioden med sikker hogst blir kortere.

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I 2009 ble rødbandsoppen registrert for første gang i Norge. De første årene var angrepene forholdsvis beskjedene, men våren 2012 ble det registrert sterke angrep i enkelte bestand. Rødbandsjuke har de siste 20 årene i stadig større omfang gjort skade på mange forskjellige furuarter og blir derfor regnet som en av de store klimavinnerne.

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Kronetilstanden hos gran, furu og bjørk som inngår i den landsrepresentative skogovervåkingen har vært stabil i 2012, og det ble observert færre biotiske og abiotiske skader enn året før. Avsetningen av svoveldioksid og sulfat har blitt redusert siden 1980 på fastlands-Norge. Derimot er det ingen tydelig trend i avsetning av uorganisk nitrogen gjennom nedbøren de siste årene. Askeskuddsyke er stadig på frammarsj i Norge, og har i 2012 spredd seg videre nordover i Sogn og Fjordane. 2012 var et gunstig år også for mange andre soppsykdommer, som einertørke, rødbandsyke på furu og toppskader på gran....

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A survey to identify ophiostomatoid fungi that infect wounds on native Norwegian and Swedish broadleaved trees was undertaken during summer 2004. A fungus resembling a species of Sporendocladia was commonly isolated from the exposed cambium and inner bark of wounds. Morphological examination and comparisons of DNA sequence data for the ITS and 5.8S regions of the rRNA gene region led to its identification as Sporendocladia bactrospora. Pathogenicity trials on young Populus tremula and Betula pubescens trees showed that S. bactrospora is capable of causing lesions on these trees. There have been few previous reports of S. bactrospora, and in most cases, these have been as saprophytes on wood. In contrast, results of this study show that it is a common inhabitant of freshly made wounds on native broadleaved trees in Scandinavia, and it appears to contribute to staining of wood.

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Shoot dieback disease of European ash caused by the ascomycete Hymenoscyphus pseudoalbidus threatens ash on a continental scale. A spore sampler placed in a diseased ash forest in Southern Norway, coupled with microscopy and DNA-based fungal species-specific real-time PCR assays, was employed to profile diurnal and within-season variation in infection pressure by ascospores of H. pseudoalbidus and the potentially co-existing non-pathogenic Hymenoscyphusalbidus. Hymenoscyphus pseudoalbidus was found to be predominant in the stand. Massive simultaneous liberation, by active discharge of pathogen ascospores in the morning, peaked in mid-Jul. to mid-Aug. Accumulation of pathogen DNA on leaflets of current-year leaves reached a high level plateau phase before appearance of autumn coloration, suggesting that pathogen establishment in leaves is terminated before the onset of leaf senescence.

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Almesjuke, som kan forårsakes av to forskjellige sopparter, har vært kjent i Norge fra 1963. Fra 1981, da den aggressive arten O. novo-ulmi kom til Norge, har sjukdommen utviklet seg raskt. Den er nå etablert rundt Oslofjorden fra Fredrikstad til Skien. Almesjuke har de senere årene spredd seg lite og i skogsområder dør forholdvis få trær slik at gjenvekst og tilvekst kompenserer for tapet.

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Winter damage caused by frost is frequently observed on common ash (Fraxinus excelsior) in Norway. In spring 2007, extensive winter damage most likely camouflaged ash dieback caused by Chalara fraxinea. In 2008, ash dieback caused by C. fraxinea had spread to large areas in the southern part of Norway. The disease was widespread in forests and nurseries, but also on roadside trees, and in gardens and parks. In 2009, the disease had spread to new areas; about 30 km into Rogaland county in southwestern Norway and also further into some valleys in southeastern Norway.

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Askeskuddbeger, Hymenoscyphus pseudoalbidus, ble registret i Norge første gang i 2008. Soppen har spredd seg med rekordfart og er nå etablert i store deler av Sør-Norge hvor det fins ask. De nordligste funnene er gjort i tre kommuner nord for Sognefjorden. Soppen infiserer blad og kommer inn i grener og stamme før bladfall. Soppen dreper små trær raskt, større trær over lenger tid. Ask er nå rødlistet grunnet denne soppen.

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Askeskuddbeger, årsak til askeskuddsjuke, er i rask spredning. Store deler av Europas askeskoger er nå infisert og i år kom den til England. I Norge har soppen, som er av asiatisk opprinnelse, snart erobret hele Vestlandet. På Østlandet og Sørlandet er mange unge trær drept. Mange store trær har lite kronemasse, men foreløpig er få av disse drept.

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Askeskuddsjuke utvikler seg stadig til det verre og nå er store deler av Vestlandet også angrepet. Foreløpig har det gått verst utover de små trærne og mange er drept. De store trærne klarer seg bedre, men noen av dem har lite kronemasse igjen.

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A large database of invasive forest pathogens (IFPs) was developed to investigate the patterns and determinants of invasion in Europe. Detailed taxonomic and biological information on the invasive species was combined with country-specific data on land use, climate, and the time since invasion to identify the determinants of invasiveness, and to differentiate the class of environments which share territorial and climate features associated with a susceptibility to invasion. IFPs increased exponentially in the last four decades. Until 1919, IFPs already present moved across Europe. Then, new IFPs were introduced mainly from North America, and recently from Asia. Hybrid pathogens also appeared. Countries with a wider range of environments, higher human impact or international trade hosted more IFPs. Rainfall influenced the diffusion rates. Environmental conditions of the new and original ranges and systematic and ecological attributes affected invasiveness. Further spread of established IFPs is expected in countries that have experienced commercial isolation in the recent past. Densely populated countries with high environmental diversity may be the weakest links in attempts to prevent new arrivals. Tight coordination of actions against new arrivals is needed. Eradication seems impossible, and prevention seems the only reliable measure, although this will be difficult in the face of global mobility.

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The relative frequency of Therrya fuckelii and T. pini fruiting on dead branches of Scots pine was investigated in southern Norway by examining lightning-damaged and wind-fallen trees, randomly collected branches and Nordic herbarium collections of these ascomycetes representing the order Rhytismatales. Ascus, ascospore, and subhymenium characteristics were used as criteria for species identification, while a sequence analysis of ITS rDNA gene cluster was performed to compare the relatedness of the species to each other and to corresponding fungal sequences available at the NCBI GenBank Sequence Database. In a few cases, the two Therrya species co-occurred on the same branch, but in general, whether field or herbarium material, T. fuckelii was clearly more common than T. pini.Within the Nordic countries, both species occurred throughout the natural distribution area of Scots pine. The ITS rDNA sequence of T. pini strains was 91% similar to T. fuckelii strains, the differences locating both within the internal transcribed spacers ITS1 and ITS2 and the 5.8 S rDNA gene. More variation in the ITS1-5.8S-ITS2 sequence was observed among T. pini than T. fuckelii samples; genetic implications of this finding are discussed. Upon sequence analysis, we discovered that a T. pini sequence has been deposited in the NCBI GenBank under a false identity. We emphasize the importance of co-examining strains that originate from mature fruit bodies with fully developed morphologic features as reference samples.

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We compared gene expression in Norway spruce secondary phloem (bark) and developing xylem (sapwood) in response to the necrotrophic pathogen Heterobasidion parviporum, wounding and methyl jasmonate (MeJ). The pathogen induced systemic and local up-regulation of PaPX3, PaPX2 and PaChi4 in both bark and sapwood that returned to constitutive levels as the plants recovered from the infection, whereas the local responses to MeJ were similar in both tissues but was longer lasting for PaPX3 and PaChi4. Genes involved in lignin biosynthesis (PaPAL1, PaPAL2, PaC4H3/5 and PaHCT1) were up-regulated locally in the bark in response to pathogen and wounding whereas MeJ induced a similar but stronger local response. The ethylene biosynthesis related transcripts PaACO and PaACS did not increase in response to MeJ treatment or the pathogen, however it increased both locally and systemically as a response to wounding in the sapwood. These results demonstrate that the local and systemic host responses to pathogen infection and wounding largely correspond and reveal striking similarities between the local response to a necrotroph, wounding and MeJ treatment in both bark and living wood.

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Ceratocystis polonica and Heterobasidion parviporum are important fungal pathogens in Norway spruce (Picea abies). Tree susceptibility to these pathogens with respect to phenology was studied using artificial fungal inoculations at six stages of bud development, and assessed by measuring phloem necroses in the stems of 2- and 8-year-old trees. Tree capacity for resistance was assessed by measuring phloem nonstructural carbohydrates at each stage. Phloem necroses were significantly larger in trees with fungal versus control inoculations and increased significantly over time. Changes in nonstructural carbohydrates occurred in the trees; a significant decline in starch and a slight but significant increase in total sugars occurred over time. These results suggest that susceptibility to fungal pathogens and carbohydrate levels in the stems of the trees were related to fine-scale changes in bud development. A trade-off may occur between allocation of starch (the major fraction of the stem carbohydrate pool) to bud development/shoot growth versus defence of the stem. Previous tests of plant defence hypotheses have focused on herbivory on plants growing under different environmental conditions, but the role of phenology and the effect of pathogens are also important to consider in understanding plant resource allocation patterns.

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Eikemjøldogg ble første gang registrert i Norge i 1911 og spredte seg meget raskt. Den er nå vidt utbredt i eikeskoger og parker fra svenskegrensa til Møre og Romsdal. Den infiserer eikeblad som ved sterke angrep kan bli helt kvitkalket.

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Arter av sopp og insekter som introduseres til nye områder kan forårsake omfattende tredød og store endringer i skogøkosystemer. Introduksjoner i andre deler av verden viser tydelig hvilket skadepotensial slike arter har. Skog og landskap søker å være i forkant med forskning som kan møte utfordringen fra nye arter i norske skoger.

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Import av tømmer og andre treprodukter kan bringe fremmede arter av insekter, sopp og planter som kan gi store skadeeffekter om de etableres i Norge. I verden kan det vises til flere eksempler på at import av nye arter med slike varer har ført til betydelig effekter på skogøkosystem og biomangfold og store kostnader for skogbruk og forvaltning. Det finnes knapt noe eksempel på at forsøk på å utrydde innførte insekter og sopp etter etablering har vært vellykket, selv når ressursinnsatsen har vært svært stor. Mange arter er vanskelig å oppdage før de allerede er godt etablert og under god spredning, og for noen arter med alvorlige effekter på skogøkosystemer har det ikke lykkes å finne gode metoder for rask påvisning til tross for omfattende innsats både i forskning og overvåking. Overvåking av tømmer og andre tre-produkter ved importsteder synes ikke å være et tilstrekkelig effektivt virkemiddel for å stoppe og utrydde fremmede arter. Dette skyldes at prøvene oftest blir for små i forhold til importvolumene og at eventuell påvisning skjer for sent til å kunne hindre etablering og videre spredning. Denne rapporten analyserer importstatistikk for siste 20 år fra ulike regioner og drøfter hvilke trender som gjør seg gjeldende for volumer av tømmer og treprodukter som potensielt kan føre med aktuelle arter av insekter, sopp og planter som en vil unngå å importere til Norge. [...]

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• Parasitism and saprotrophic wood decay are two fungal strategies fundamental for succession and nutrient cycling in forest ecosystems. An opportunity to assess the trade-off between these strategies is provided by the forest pathogen and wood decayer Heterobasidion annosum sensu lato. • We report the annotated genome sequence and transcript profiling, as well as the quantitative trait loci mapping, of one member of the species complex: H. irregulare. Quantitative trait loci critical for pathogenicity, and rich in transposable elements, orphan and secreted genes, were identified. • A wide range of cellulose-degrading enzymes are expressed during wood decay. By contrast, pathogenic interaction between H. irregulare and pine engages fewer carbohydrate-active enzymes, but involves an increase in pectinolytic enzymes, transcription modules for oxidative stress and secondary metabolite production. • Our results show a trade-off in terms of constrained carbohydrate decomposition and membrane transport capacity during interaction with living hosts. Our findings establish that saprotrophic wood decay and necrotrophic parasitism involve two distinct, yet overlapping, processes.

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Furuas knopp- og grentørkesopp er en av furuskogens verste skadegjørere, og forårsaker år om annet store tap. Det største angrepet skjedde i 2001, da enorme områder i Sør-Norge og Sør-Sverige ble berørt. Milde høster og ustabile vintre kan føre til flere slike angrep.

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Vi har flere arter av honningsopp i Norge, og to av dem, skog- og hagehonningsopp, er svært aktive ute i skogen. Begge artene forårsaker innråte i trær, men kan også opptre mer aggressivt og drepe svekkede trær nokså raskt. Honningsopp er involvert i grantørke som i de senere årene har utviklet seg til det verre, trolig i takt med klimaendringer.

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Ospeflekk er en forholdsvis ukjent skadegjører som i forrige århundre bare var rapportert noen få ganger i Norge. De siste 10 årene har det imidlertid skjedd enn eksplosjonsartet oppblomstring, noe som kan skyldes endringer i klima. Og soppen ser ut til å spre seg til nye områder.

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Phytophthora-arter er aggressive, sopplignende skadegjørere som fremmes av fuktig og mildt klima. I Norge er flere arter oppdaget på trær i paker eller skogholt nær hager. Varslede klimaendringer med økt temperatur og nedbør kan skape gode vekstforhold slik at flere arter kan etablere seg også i skogområder.

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Vi har to arter av rotkjuke i Norge, gran- og fururotkjuke. Som navnet sier har de hvert sitt treslag som hovedvert, men begge kan gå på andre treslag, også løvtrær. Soppens spesielle biologi gjør at en kan forvente økede råteproblemer grunnet klimaendringer. Økt stormaktivitet gir mer rotrykking og lettere tilgang for rotkjuke, mens mildere klima med lengre vekstsesong gjør at perioden med sikker hogst blir kortere.

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I 2009 ble rødbandsoppen registrert for første gang i Norge. De første par årene var angrepene forholdsvis beskjedne, men våren 2012 er det registrert sterke angrep i enkelte bestand. Rødbandsjuke har de siste 20 årene i stadig større omfang gjort skade på mange forskjellige furuarter og blir derfor regnet som en av de store klimavinnerne.

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Background: NB-LRR resistance proteins are involved in recognizing pathogens and other exogenous stressors in plants. Resistance proteins are the first step in induced defence responses and a better understanding of their regulation is important to understand the mechanisms of plant defence. Much of the post-transcriptional regulation in plants is controlled by microRNAs (miRNA). We examined the expression of five Norway spruce miRNA that may regulate NB-LRR related transcripts in secondary phloem (bark) of resistant Norway spruce after wounding and inoculation with the necrotrophic blue stain fungus Ceratocystis polonica. Results: The plants of this clone recovered from both the pathogen inoculations and wounding alone. We found local and systemic induction of the resistance marker genes PaChi4, PaPAL and PaPX3 indicative of an effective induced host defence response. There were minor local and systemic changes in the expression of five miRNAs and 21 NB-LRRs between healthy and treated plants. Only five putative NB-LRRs (PaLRR1, PaLRR3, PaLRR14, PaLRR15 and PaLRR16) showed significant increases greater than two-fold as a local response to C. polonica. Of all NB-LRRs only PaLRR3, the most highly differentially regulated NB-LRR, showed a significant increase also due to wounding. The five miRNAs showed indications of an initial local and systemic down-regulation at day 1, followed by a later increase up to and beyond the constitutive levels at day 6. However, the initial down-regulation was significant only for miR3693 and miR3705. Conclusions: Overall, local and systemic expression changes were evident only for the established resistance marker genes and PaLRR3. The minor expression changes observed both for the followed miRNAs and their predicted NB-LRR targets suggest that the expression of most NB-LRR genes are maintained close to their constitutive levels in stressed and healthy Norway spruce plants.

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Toppskader på gran i ungskog kan gi store økonomiske tap da det kan bli gankvist eller dobbelttopper i den mest verdifulle delen av stammen. Nå har to uvanlige sopper slått til, og i de mest berørte bestandene kan opp mot to tredjedeler av trærne ha fått skader.

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Orerust er vidt utbredt i Sør-Norge og et stykke nord i Nordland. Etter introduksjon til Europa har den spredd seg meget raskt. Den infiserer oreblad og ved sterke angrep kan det bli tidlig bladfall. Gråor blir lettere angrepet enn svartor.

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I 2011 var det en nedgang i helsetilstanden hos bartrær, og hos gran ble det observert en del toppskranting og avdøing i hogstklasse 3 og 4. Vi registrerte få insekt- og soppskader på gran der 1 % av trærne var angrepet, mens 1,2 % av furutrærne hadde slike biotiske skader. Antall abiotiske skader (stort sett snø- og vindrelaterte) hos bartrærne var omtrent på samme nivå som tidligere i overvåkingsperioden (1,7 og 1,2 % for hhv. gran og furu). Av treslagene gran, furu og bjørk er det fortsatt bjørk som er mest utsatt for skader: 10,6 % av bjørketrærne var angrepet og skadet av insekter, hovedsakelig av fjellbjørkemåleren, mens 14,2 % av bjørketrærne var angrepet av bjørkerustsopp eller andre sopper og 3,5 % hadde skader med abiotiske årsaker....

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The ascomycete fungus Hymenoscyphus pseudoalbidus (anamorph Chalara fraxinea) is responsible for ash dieback currently expanding over large parts of Europe. Our objective was to investigate the genetic structure of H. pseudoalbidus and to examine its relationship to the species H. albidus, known as a saprotroph. The study comprised 181 isolates of H. pseudoalbidus collected within the diseased area, 17 H. albidus isolates from six apothecia, collected outside the diseased area in Norway, and nine apothecia of H. pseudoalbidus collected in Sweden. By analysis of microsatellite markers developed for this study, combined with AP-PCR using the M13 primer, we demonstrated sexual heterothally in H. pseudoalbidus, detected high gene flow and low geographic structure of the H. pseudoalbidus population and found indications of a founder effect. Also, substantial genetic differences were detected between the two species of fungi; only four of seven microsatellite markers developed for H. pseudoalbidus were amplified for H. albidus, and no alleles were shared among the species. Furthermore, AP-PCR banding patterns were distinctly different for the two species. We conclude that even though the two fungi have a similar habitat and are morphologically virtually identical, they do not share a recent common ancestor.

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Mycosphaerella pini med det anamorfe stadiet Dothistroma septosporum er nå kjent fra to kommuner i Troms, Bardu og Målselv, og mange steder i sør-øst Norge. Soppen infiserer furunåler under fuktige forhold og forårsaker en sjukdom kalt rødbandsjuke.

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Aspen trees are exposed to a range of attackers and employ varied strategies to reduce their impact. The diversity of responses may have importance for resistance properties at the stand level, and justifies the search for varied defensive strategies in natural populations. We used transcriptomic tools to evaluate diverse responses at the gene activity level in Populus tremula in response to wounding, and to inoculation with two pathogenic fungi (Melampsora magnusiana vs Ceratocystis sp.) that differ in life style (biotroph vs necrotroph) and host tissue requirement (live leaf vs dead wood tissues). Two aspen genotypes from the SwAsp collection with differences in growth and phenolic composition were used to study differences in resistance properties. High defence gene induction, high growth and elevated defence properties toward the biotroph appeared to support each other in this study exemplified in the more resistant SwAsp clone, whereas the more susceptible SwAsp clone was much less responsive to infections, and displayed more symptoms when infected with M. magnusiana. Interestingly, in the more resistant clone wounding gave greater systemic activity of selected candidate genes than when combined with the necrotroph, suggesting that this pathogen has some ability to suppress the induction or translocation of the systemic defence signal in this particular clone.

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I 2009 ble rødbandsjuke første gang registrert i norge, i Bardu og Målselv kommuner i Troms. I 2010-12 er sjukdommen observert i tre områder på Østlandet. Fram til 2012 var angrepne beskjedne, men i år var det kraftige angrep i enkelte bestand, noe som vakte stor oppmerksomhet på en internasjonal konferanse om denne sjukdommen.

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The GH61 represents the most enigmatic Glycoside Hydrolase Family (GH) regarding putative enzymatic activity and importance in cellulose degradation. Heterobasidion irregulare is a necrotizing pathogen and white rot fungus, causing enormous damages in conifer forests.The genome of H. irregulare allowed identification of ten HiGH61 genes. qRT-PCR analysis separate the HiGH61 members into two groups; one that show up regulation on lignocellulosic substrates and another that show either down regulation or constitutive expression. This grouping suggests that the fungus relates different sets of GH61s for different substrates, like in the various stages of necrotizing and saprophytic growth on the host.One HiGH61 showed up to 17000 fold increase on spruce heartwood suggesting a pivotal role in cellulose decomposition during saprophytic growth. Sequence analysis of these genes reveals that all GH61s but one possess the conserved metal binding motif predicted to be essential for activity.The sequences also divide into groups having either an insert near the N-terminus or an insert near the second catalytic histidine, which both may represent extensions of the substrate binding surface. Three HiGH61s encode cellulose-binding modules (CBM1), indicating direct targeting of crystalline cellulose, two being up regulated on pure cellulose.There was a common substrate-specific induction patterns of the HiGH61s with several reference cellulolytic and hemicellulolytic GHs, this taken together with their low levels on media lacking lignocellulose, reflect the concerted nature of cell wall polymer degradation.

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A 1149 bp genomic fragment corresponding to the 5' non-coding region of the PgD1 (Picea glauca Defensin 1) gene was cloned, characterized, and compared with all Arabidopsis thaliana defensin promoters. The cloned fragment was found to contain several motifs specific to defence or hormonal response, including a motif involved in the methyl jasmonate reponse, a fungal elicitor responsive element, and TC-rich repeat cis-acting element involved in defence and stress responsiveness. A functional analysis of the PgD1 promoter was performed using the uidA (GUS) reporter system in stably transformed Arabidopsis and white spruce plants. The PgD1 promoter was responsive to jasmonic acid (JA), to infection by fungus and to wounding. In transgenic spruce embryos, GUS staining was clearly restricted to the shoot apical meristem. In Arabidopsis, faint GUS coloration was observed in leaves and flowers and a strong blue colour was observed in guard cells and trichomes. Transgenic Arabidopsis plants expressing the PgD1::GUS construct were also infiltrated with the hemibiotrophic pathogen Pseudomonas syringae pv. tomato DC3000. It caused a suppression of defensin expression probably resulting from the antagonistic relationship between the pathogen-stimulated salicylic acid pathway and the jasmonic acid pathway. It is therefore concluded that the PgD1 promoter fragment cloned appears to contain most if not all the elements for proper PgD1 expression and that these elements are also recognized in Arabidopsis despite the phylogenetic and evolutionary differences that separates them.

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Pathogen challenge of tree sapwood induces the formation of reaction zones with antimicrobial properties such as elevated pH and cation content. Many fungi lower substrate pH by secreting oxalic acid, its conjugate base oxalate being a reductant as well as a chelating agent for cations. To examine the role of oxalic acid in pathogenicity of white-rot fungi, we conducted spatial quantification of oxalate, transcript levels of related fungal genes, and element concentrations in heartwood of Norway spruce challenged naturally by Heterobasidion parviporum. In the pathogen-compromised reaction zone, upregulation of an oxaloacetase gene generating oxalic acid coincided with oxalate and cation accumulation and presence of calcium oxalate crystals. The colonized inner heartwood showed trace amounts of oxalate. Moreover, fungal exposure to the reaction zone under laboratory conditions induced oxaloacetase and oxalate accumulation, whereas heartwood induced a decarboxylase gene involved in degradation of oxalate. The excess level of cations in defense xylem inactivates pathogen-secreted oxalate through precipitation and, presumably, only after cation neutralization can oxalic acid participate in lignocellulose degradation. This necessitates enhanced production of oxalic acid by H. parviporum. This study is the first to determine the true influence of white-rot fungi on oxalate crystal formation in tree xylem.

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Grantrær og barkbiller har slåss i millioner av år. Kunnskap om granas forsvar kan gjøre det mulig å redusere barkbilleskader gjennom planteforedling og skogskjøtsel. Ny forskning viser at grantrær kan unngå å bli drept av barkbiller hvis de er raske til å produsere mye kvae.

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Heterobasidion parviporum, a common pathogenic white-rot fungus in managed Norway spruce forests in northern and central Europe, causes extensive decay columns within stem heartwood of the host tree. Infected trees combat the lateral spread of decay by bordering the heartwood with a fungistatic reaction zone characterized by elevated pH and phenol content. To examine the mode of fungal feeding in the reaction zone of mature Norway spruce trees naturally infected by H. parviporum, we conducted spatial proWling of pectin and hemicellulose composition, and established transcript levels of candidate fungal genes encoding enzymes involved in degradation of the diVerent cell wall components of wood. Colonized inner heartwood showed pectin and hemicellulose concentrations similar to those of healthy heartwood, whereas the carbohydrate proWles of compromised reaction zone, irrespective of the age of fungal activity in the tissue, indicated selective fungal utilization of galacturonic acid, arabinose, xylose and mannose. These data show that the rate of wood decay in the reaction zone is slow. While the up-regulation of genes encoding pectinases and hemicellulases preceded that of the endoglucanase gene during an early phase of fungal interaction with xylem defense, the manganese peroxidase gene showed similar transcript levels during diVerent phases of wood colonization. It seems plausible that the reaction zone components of Norway spruce interfere with both lignin degradation and the associated co-hydrolysis of hemicelluloses and pectin, resulting in a prolonged phase of selective decay.

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Dieback of European ash (Fraxinus excelsior), caused by the ascomycete Hymenoscyphus pseudoalbidus (anamorph Chalara fraxinea), started around 1992 in Poland and has since then spread over large geographical areas. By November 2010, the disease had been recorded in 22 European countries. The gradual expansion and high intensity of the ash dieback epidemic in Europe may suggest that H. pseudoalbidus is an invasive alien organism. In Norway, ash dieback was first reported in spring 2008, and a survey in early summer of the same year revealed that the disease had spread over large parts of the southern and eastern regions of the country. The distance from the southernmost to the northernmost infected stands was, at that time, about 400 km. Some old necrotic lesions were also observed, indicating that the ash dieback pathogen is likely to have been present in Norway since at least 2006. In 2009, a spore sampler was installed in a diseased ash stand at Ås, South-Eastern Norway. Sampling started in late July and continued until late September. Large numbers of ascospores resembling those of H. pseudoalbidus were observed, with the maximum number of spores occurring from the end of July to mid-August. The deposition of ascospores occurred mainly between 6 and 8 a.m. Ascospores are most likely to be the primary source initiating host infections and responsible for the rapid recent spread of H. pseudoalbidus in Europe.

Sammendrag

A rapid increase in the frequency of Dutch elm disease (DED), a wilting disease of elm trees caused by bark-beetle vectored fungi, was observed in the early 1990s on several wych elm stands around Oslofjord, southern Norway. To examine the current status of the disease and its impacts on elm population, disease frequency and size distribution of elms were recorded at four locations. Northern parts of Lier, a municipality most affected by DED in Norway 15 years ago, showed in the survey season 4% disease frequency, whereas 13.8% of trees were dead, the dead trees having accumulated over several years in the unmanaged stands. In southern parts of the municipality the mean disease and death percentages were 1.9 and 2.4%. Compatible with their low disease incidence in early 1990s, the other two areas now examined, municipality of Larvik and district of Grenland, showed comparably low frequency of DED. Northern part of Lier showed significantly higher overall density of elm trees per hectare than the other examined areas, and also the small elms below 5 cm in d.b.h. were most frequent in this region. In contrast, the density of large trees was lower in northern Lier than in the other examined areas. These data suggest that regeneration of the tree is not prohibited owing to the disease but that the large trees have been locally reduced in frequency as a result of DED. The superior general density of elm trees in northern Lier, owing to the exceptionally rich soil in the warm southern slopes of the region,> may have contributed to the rapid increase of DED in the area 15 years ago and to the subsequent settlement of the disease outbreak as a chronic stage.

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The occurence of Armillaria species was assessed in Norway, enabling the northern-most distribution of this genus to be determined in Europe. Four Armillaria species were found in Norway. Armillaria borealis was the most common species occurring on woody vegetation to the permafrost zone (ca. 69°N). Armillaria cepistipes was present in southern and central Norway, but was not found further than 66°N. Armillaria solidipes and Armillaria gallica were rare, found at only one locality each; 59°40′ and 59°32′, respectively. Armillaria species were found on 14 hosts, but there was no significant difference between occurrence of A. borealis and A. cepistipes on declining and dead trees. Phylogenetic analyses separated each species into separate clades. All isolates of A. borealis, except one, and most isolates of A. solidipes were in separate clades. However, a subclade within the A. borealis clade was formed of two A. ostoyae and one A. borealis isolates. Two small A. cepistipes genets were found in a declining oak stand.

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During a survey conducted in August 2009 in northern Norway, symptoms typical for red band needle blight (1) were observed in four young Scots pine (Pinus sylvestris) stands. The stands, less than 15 years old, were located in humid sites near rivers in Bardu and Målselv municipalities, Troms County. Many of the oldest needles (2- to 3- years-old) in the lower part of young trees were partially or completely brown, but still attached, and red bands could be observed. Aggregations of conidial stromata were often seen in the red bands. Conidia were hyaline, smooth, thin walled, and filiform, 1.9 to 2.6 μm wide and 12 to 36 μm long....

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In forest soils, saprotrophic, necrotrophic and ectomycorrhizal fungi are involved in carbon cycling. Heterobasidion annosum, white rot necrotrophic fungi, is known to decompose wood lignocellulose by secreting a broad range of oxidative enzymes. The genome H. annosum s.l. was sequenced by JGI to a 8.23X coverage and assembled into 39 scaffolds with a total size of 33.7 Mb covering more than 98% of the whole genome. Based on the genome sequence we have characterized gene families coding for enzymes known to participate in conversion of wood lignin: multicopper oxidases (MCOs, 18 genes) as laccases (Lcc), class II peroxidases (8 genes) as manganese peroxidases (MnP), glyoxal oxidases (5 genes, GLOX), quinone-reducing oxidoreductases (19 genes, QOR) and GMC oxidoreductases (12 genes) as aryl alcohol oxidases (AAO). We studied the genomic organisation and phylogeny of these genes as well as their expression using qRT-PCR. Comparative and phylogenetic analyses of genes coding for enzymes involved in wood lignin conversion and decomposition (i.e. lignin-modifying class II peroxidases) reveal differences between white- and brown-rot, necrotrophic and saprotrophic wood-decaying basidiomycetes. Transcript profiling using qRT-PCR revealed that some transcripts were very abundant in lignin-rich media, in cellulose-rich media, in wood or in the free-living mycelium grown liquid culture, suggesting specific functions of these genes, which need to be studied further.

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The causative agent of dieback on European ash (Fraxinus excelsior) was first described as Chalara fraxinea based on cultural morphology because no sexual stage of the fungus was known. Later, based on culturing of ascospores of a candidate teleomorph, morphological comparison and nuclear ribosomal internal transcribed spacer sequencing, the sexual stage of C. fraxinea was assigned as Hymenoscyphus albidus, a native and widespread species in Europe. Recently, the morphological species concept of H. albidus was shown to cover two species that cannot be separated from each other based on teleomorph characters, but which can be distinguished by several DNA markers. As a result, the strains causing ash dieback were reassigned as H. pseudoalbidus. The closely related H. albidus is presumably a non-pathogenic endophyte, but pathogenicity tests to confirm this hypothesis have not yet been performed. Genotyping of herbarium specimens has shown that H. pseudoalbidus was present in Switzerland for at least a decade prior to the epidemic outbreak in Europe. The origin of the ash dieback pathogen, and the general importance of correct pathogen identification to development of effective disease control, are discussed.

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Background: Tree-killing bark beetles (Coleoptera, Scolytinae) are among the most economically and ecologically important forest pests in the northern hemisphere. Induction of terpenoid-based oleoresin has long been considered important in conifer defense against bark beetles, but it has been difficult to demonstrate a direct correlation between terpene levels and resistance to bark beetle colonization. Methods: To test for inhibitory effects of induced terpenes on colonization by the spruce bark beetle Ips typographus (L.) we inoculated 20 mature Norway spruce Picea abies (L.) Karsten trees with a virulent fungus associated with the beetle, Ceratocystis polonica (Siem.) C. Moreau, and investigated induced terpene levels and beetle colonization in the bark. Results: Fungal inoculation induced very strong and highly variable terpene accumulation 35 days after inoculation. Trees with high induced terpene levels (n = 7) had only 4.9% as many beetle attacks (5.1 vs. 103.5 attacks m22) and 2.6% as much gallery length (0.029 m m22 vs. 1.11 m m22) as trees with low terpene levels (n = 6). There was a highly significant rank correlation between terpene levels at day 35 and beetle colonization in individual trees. The relationship between induced terpene levels and beetle colonization was not linear but thresholded: above a low threshold concentration of ,100 mg terpene g21 dry phloem trees suffered only moderate beetle colonization, and above a high threshold of ,200 mg terpene g21 dry phloem trees were virtually unattacked. Conclusion/Significance: This is the first study demonstrating a dose-dependent relationship between induced terpenes and tree resistance to bark beetle colonization under field conditions, indicating that terpene induction may be instrumental in tree resistance. This knowledge could be useful for developing management strategies that decrease the impact of tree-killing bark beetles.

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Rødbandsjuke er for første gang observert i Norge. Sjukdommen som på engelsk kalles Red band needle blight forårsakes av en sopp som står på Mattilsynets liste over sjukdommer som er forbudt å innføre til Norge. Angrep fører til tidlig nålefall og tilveksttap. Ved sterke angrep drepes trea. De første funna ble gjort i Troms, men nå er soppen også funnet i to fylker i Sør- Norge. Alle funna er gjort i ungskog....

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Askeskuddsjuke er på frammarsj i Norge og i Europa. I 2010 var det imidlertid ikke så dramatisk som året før, men på våre overvåkingsflater har vi registrert en liten nedgang i kronetetthet. Så det er all grunn til fortsatt bekymring. Det er stor forskningsaktivitet i mange land, og nå vet vi også hvilken sopp som er årsaken. I tillegg begynner det å komme rapporter om andre askearter som er mottakelige for sjukdommen.

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Helsetilstanden hos bartrær må betegnes som tilfredsstillende, men hos gran ble det observert en del toppskranting og avdøing i hogstklasse 3 og 4. Vi registrerte få insekt- og soppskader på gran der 0,4 % av trærne var skadet, mens 1,7 % av furutrærne hadde slike biotiske skader. Antall nye toppbrekk, vindfall og andre snø- og vindrelaterte skader hos bartrærne var omtrent på samme nivå som tidligere i overvåkingsperioden (hhv. 1,2 og 1,4 % for gran og furu). Av treslagene gran, furu og bjørk er det fortsatt bjørk som er mest utsatt, der 9,4 % av bjørketrærne var angrepet og skadet av insekter, hovedsakelig av fjellbjørkemåleren, mens 9,2 % av bjørketrærne var angrepet av bjørkerustsopp og 3 % hadde skader med abiotiske årsaker.....

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Arter innen Phytophthora-slekten kan forårsake alvorlige sykdommer på trær. Økende handel påskynder spredning av ulike plantepatogener, og det er flere eksempler på at nye sykdommer forårsaket av arter innen Phytophthora-slekten er under utvikling i Europa.

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Klimaendringer og økt handel og transport landa imellom utgjør den største trusselen for introduksjoner av nye skadegjørere. Mycosphaerella pini er en av soppene som de senere åra har spredt seg til nye områder og som i økende grad fører til skog skader rundt omkring i verden. Soppen forårsaker sjukdommen som på engelsk blir kalt "Red band needle blight" så rødbandsjuke er et naturlig navn på norsk. Angrep fører til tidlig nålefall og redusert tilvekst. Ved sterke angrep kan trea dø. Soppen er nå funnet i Norge; i Troms og i to fylker i Sør-Norge. Alle funna er gjort i ungskog.

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Rødbandsjuke på furu er nå funnet i Norge. Sjukdommen, som på engelsk kalles “red band needle blight” eller “Dothistroma needle blight”, er forårsaket av en sopp som står på Mattilsynets liste over sjukdommer det er forbudt å innføre til Norge. Den ble først funnet i Troms, men soppen er også funnet i to fylker i Sør-Norge. Foreløpig er den bare funnet på trær i skog, men mange innførte furuarter er utsatt for smitte.

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Introduction: Windstorm is one of the most destructive environmental disturbance factors on forests, but its influence on conifer defense chemistry and susceptibility to insects and diseases is not well understood. Materials and methods: We selected groups of 10 Norway spruce trees with short leaders, leaning stems, or no apparent damage 17 months after the largest storm ever recorded in Sweden. Trees were mass-inoculated with Ceratocystis polonica, a virulent blue stain fungus associated with the spruce bark beetle (Ips typographus) to estimate tree resistance. Terpene and phenolic composition in the bark was analyzed by gas chromatography–mass spectrometry, two-dimensional gas chromatography, and liquid chromatography. Results: In contrast to our hypothesis, the results showed that trees with no apparent damage were more susceptible to C. polonica inoculation than short-leader and leaningstem trees. Chemical composition also differed between trees in different damage classes. (+)-3-carene and two unidentified stilbenes were higher, and taxifolin glycoside was lower in trees without apparent damage than in the others. The relative amount of (−)-α-pinene was negatively correlated, whereas (+)-3-carene, sabinene, (−)-germacrene D, thunbergol and two unidentified stilbenes were positively correlated with fungal performance. Conclusions: These results suggested that wind damage had increased resistance level of short-leader and leaning trees to C. polonica inoculation, and that change in terpene and phenolic composition in the bark could be at least partly responsible for the induced resistance. Different possible explanations for this unexpected finding are discussed.

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Enkelte mener å ha observert at det var mindre skader på asketrær i 2010 enn året før og tror at bekymringen for askens framtid er betydelig overdreven. På våre overvåkingsflater har vi i 2010 registrert en liten nedgang i kronetetthet, og vi ser også at askeskuddsjuken er på stadig frammarsj både i Norge og i Europa ellers. Så det er all grunn til fortsatt bekymring.

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Plants are exposed to a variety of pathogens in their natural habitats. To understand the key processes of defense responses in aspen (Populus tremulae) at the transcript level two clones C72 and C23 with differential level of resistance from the SwAsp collection were inoculated with a foliar rust (Melampsora magnusiana Wagnar). Leaf samples were collected from adjacent areas of the inoculation site to examine the long distance (systemic) defense responses at day1, day3 and day14 post treatments. We performed microarray experiments on the biothrophic interaction, on comparison with the healthy controls we found that the two clones respond in a widely different fashion to the rust. Clone C23 showed almost no response to biotroph after 24 hours while clone 72 gave a clear defense response to the pathogen. Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) showed a significant differential expression patterns in susceptible and resistant colnes. Chitinase, cinnamic acid reductase and the iaa genes showed signification up-regulation in resistant clone. The level of expression was 5.9 delta threshold cycles in chitinase gene at day14. Data analysis from extracted total phenolics and condensed tannins verify the results of cDNA arrays and qRT-PCR.

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Development in surface mould growth on painted/unpainted wooden claddings and acting climatic factors were investigated over a period of 3 years. Eight wood substrates, including modified, preservative-treated and untreated wood, were tested in combination with three types of paint: (1) water-borne alkyd modified acrylic paint without fungicide; (2) solvent-borne alkyd paint without fungicide; and (3) ICP (internal comparison product). One set of samples was exposed unpainted. The samples were tested according to a modified version of EN 927-3. A logistic regression model was fitted to the data. The degree of mould growth varied with exposure time, coating typology, wood substrate, temperature and relative humidity. Exposure time and coating typology contributed most to the model. After 3 years of outdoor exposure unpainted panels and panels coated with solvent-borne paint without fungicide had more mould growth than panels coated with ICP and water-borne paint without fungicide. Unpainted oil/copper–organic preservative-treated claddings had higher resistance to mould growth than other unpainted wood substrates. Coated untreated pine and coated acetylated pine were more susceptible to mould growth than other coated wooden substrates.

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The genome H. annosum s.l. was sequenced by JGI to a 8.23X coverage and assembled into 39 scaffolds with a total size of 33.7 Mb covering more than 98% of the whole genome. Based of genome sequence we annotated a number of genes for fungal enzymes that are believed to participate in lignin degradation, including: laccases (Lcc18 genes), manganese peroxidases (MnP8 genes) and hydrogen peroxide forming enzymes such as glyoxal oxidases (GLOX5 genes), quinone oxidoreductases (QOR17 genes) and aryl alcohol oxidases (AAO16 genes), which is in concordance with these gene family sizes observed in other sequenced white-rot fungi. We studied the genomic organisation and phylogeny of these genes as well as their expression using NimbleGen arrays and qRT-PCR. Transcript profiling using whole-genome oligo arrays and qRT-PCR revealed that some transcripts were very abundant in lignin-rich media (Lcc5 15, MnP2, GLOX4, QOR2 10, AAO9), in cellulose-rich media (lcc2, 7 16, MnP3 4, GLOX3, QOR4 6, AAO2, 7 10), in wood (Lcc3, MnP4, QOR2, GLOX1, AAO10) or in the free-living mycelium grown liquid culture (Lcc1, 3, 10 13), suggesting specific functions of these genes, which need to be studied further.

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Microbial disfigurement of coated wooden surfaces is considered a major maintenance concern and will shorten the aesthetic service life of wooden facades. The effect of the physical surface structure of a paint film when applied on wood may have an impact on the susceptibility to mould growth. Six model paints were formulated to give the following physical surface structures: glossy, matt, soft, hard, hydrophobic, and a film with air inclusion. The model paints and a standard paint, with and without fungicide, were applied on panels of Norway spruce (Picea abies L Karst.) and exposed outdoors for nearly three years according to a modified version of EN 927-3. A logistic regression model was fit to the data, and the degree of mould growth varied with exposure time and type of paint. Hard model paint was significantly more susceptible than the other model paints and had a performance close to the standard paint without fungicide. Soft model paint provided the best performance, with the least mould growth. Temperature, relative humidity, and precipitation did not significantly contribute to the model. (C) 2010 Elsevier Ltd. All rights reserved.

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Ophiostoma spp. include important pathogens of trees and causal agents of sapstain. These fungi infect wounds on trees and are typically carried by insects, especially bark beetles. Ophiostoma spp. on coniferous hosts in the Northern Hemisphere are well-known. However, other than for the serious pathogens O. ulmi and O. novo-ulmi, very little research has been done on the occurrence of this group of fungi on native broad-leaved trees, especially in the Nordic countries. In this study, surveys were conducted in several areas of Norway to isolate Ophiostoma spp. associated with wounds on native broad-leaved trees belonging to the genera Betula, Fagus, Quercus, Sorbus and Tilia. Morphological studies and comparisons of DNA sequences for the ITS, 5.8S and part of the beta-tubulin gene regions were used to confirm the identity of the fungi collected. Ophiostoma spp., and especially their Pesotum anamorphs, were common on wounds on the trees sampled. In most cases, they were associated with wood stain. Ophiostoma spp. collected included predominantly O. quercus, O. borealis sp. nov., and O. denticiliatum. The results of this study emphasize that the diversity of Ophiostoma spp. on broad-leaved trees is still incompletely understood in Norway and other European countries.

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Helsetilstanden hos bartrær må betegnes som tilfredsstillende, men hos gran ble det observert en del toppskranting og avdøing i hogstklasse 3 og 4. Vi registrerte få insekt- og soppskader på gran der 0,4% av trærne var skadet, mens 1,5% av furutrærne hadde slike biotiske skader. Antall nye toppbrekk, vindfall og andre snø- og vindrelaterte skader var omtrent på samme nivå som tidligere i overvåkingsperioden. Kronetettheten utviklet seg positivt for treslagene gran, furu og bjørk i 2009, selv om bjørk fortsatt har lav gjennomsnittelig kronetetthet. Kronefargen utviklet seg også positivt for bartrærne med 1,6% flere gran- og 5,5% flere furutrær med frisk kronefarge i 2009 enn i 2008. For bjørk ble det derimot registrert 1% færre trær med frisk grønn farge. Det er de eldste trærne som er mest utsatt for kroneutglisning og misfarging. Helsetilstanden til trær, registrert ved kronetetthet, misfarging og skader, påvirkes i stor grad direkte av værforhold som tørke, frost og vind, eller indirekte ved at været påvirker omfanget av soppsykdommer og insektangrep. Langtransporterte luftforurensninger kan komme i tillegg til eller virke sammen med klimatiske forhold.....

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The blue-stain fungus Ceratocystis resinifera colonizes wounds on living Picea spp. and other conifers in Europe and North America. Little is known regarding the pathogenicity of this fungus and consequently, four Norwegian C. resinifera isolates were inoculated on to Norway spruce (Picea abies) using two different techniques. These included single-point inoculations on young trees (two inoculations per tree on 14-year-old trees) and mass-inoculations on older trees (∼200 inoculations per tree on 34-year-old trees). In both experiments, C. resinifera induced minor symptoms that in most cases did not differ significantly from inoculation with sterile agar. The virulent blue-stain fungus C. polonica, which was inoculated for comparative purposes, induced extensive symptoms, causing 83% dead cambium circumference and 82% blue-stained sapwood, and long necrotic lesions in the phloem. The results suggest that C. resinifera is non-pathogenic or only mildly pathogenic to Norway spruce and does not present a threat to these trees.

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Så lenge trær unngår angrep av skadelige organismer, kan de leve i mange hundre år. Men med alderen blir trærne mindre motstandsdyktige mot forskjellige infeksjoner, og det største problemet er gjerne råte. Råte er først og fremst et aldersfenomen. Jo eldre trærne blir, jo lettere blir de utsatt for råteinfeksjoner.

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Rotkjuke, Heterobasidion annosum s.l. er et stort problem i de nordlige barskogsområder. I Norge er hele 20 prosent av grantrærne angrepet av denne skadesoppen. Dette fører ikke bare til at tømmeret blir ubrukelig til de fleste formål, men også til frigjøring av mye CO2 som ellers ville vært bundet i trærne. Rotkjuka angriper via rotkontakter. Dette skjer ofte via stubber av felte nabotrær etter hogst eller tynning. Soppen ødelegger stammen opp til tolv meter fra bakkenivå.

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Constitutive and inducible terpene production is involved in conifer resistance against bark beetles and their associated fungi. In this study 72 Norway spruce (Picea abies) were randomly assigned to methyl jasmonate (MJ) application, inoculation with the bluestain fungus Ceratocystis polonica, or no-treatment control. We investigated terpene levels in the stem bark of the trees before treatment, 30 days and one year after treatment using GC–MS and two-dimensional GC (2D-GC) with a chiral column, and monitored landing and attack rates of the spruce bark beetle, Ips typographus, on the trees by sticky traps and visual inspection. Thirty days after fungal inoculation the absolute amount and relative proportion of (+)-3-carene, sabinene, and terpinolene increased and (+)-α-pinene decreased. Spraying the stems with MJ tended to generally increase the concentration of most major terpenes with minor alteration to their relative proportions, but significant increases were only observed for (−)-β-pinene and (−)-limonene. Fungal inoculation significantly increased the enantiomeric ratio of (−)-α-pinene and (−)-limonene 1 month after treatment, whereas MJ only increased that of (−)-limonene. One year after treatment, both MJ and fungal inoculation increased the concentration of most terpenes relative to undisturbed control trees, with significant changes in (−)-β-pinene, (−)-β-phellandrene and some other compounds. Terpene levels did not change in untreated stem sections after treatment, and chemical induction by MJ and C. polonica thus seemed to be restricted to the treated stem section. The enantiomeric ratio of (−)-α-pinene was significantly higher and the relative proportions of (−)-limonene were significantly lower in trees that were attractive to bark beetles compared to unattractive trees. One month after fungal inoculation, the total amount of diterpenes was significantly higher in putative resistant trees with shorter lesion lengths than in putative susceptible trees with longer lesions. Thus, terpene composition in the stem bark may be related to resistance of Norway spruce against I. typographus and C. polonica.

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The anamorph genus Leptographium Lagerberg and Melin includes species that are typically bark beetleassociated fungi, with teleomorphs in Grosmannia. During a survey of ophiostomatoid fungi in Norway, two unusual species, that fit the broader morphological description of Leptographium, were isolated directly from the rootfeeding beetles, Dryocetes authographus and Hylastes cunicularius, as well as from roots infested by these insects. The first of these could be distinguished from other described species based on a sparse sporulation, black spore drops and chlamydospores in older cultures. This species also produces a Hyalorhinocladiella synanamorph. The second species was characterised by distinctly curved conidia. Based on these unusual morphological characteristics and distinct DNA sequences, these fungi were recognised as new taxa for which the names Leptographium chlamydatum sp. nov. and L. curvisporum sp. nov. are provided.

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European ash (Fraxinus excelsior), also known as common ash, occurs naturally inland in lower areas of southeastern Norway and along the southern coast of the country. It is important both as a forest and ornamental tree. During the last decade, dieback has become a disastrous disease on F. excelsior in many European countries. The anamorphic fungus Chalara fraxinea T. Kowalski (1), described for the first time from dying ash trees in Poland, is now considered the cause of ash dieback (2). In May of 2008, C. fraxinea was isolated from 1.5 m high diseased F. excelsior in a nursery in Østfold County in southeastern Norway. Symptoms included wilting, necrotic lesions around leaf scars and side branches, and discoloration of the wood. From symptomatic branches, small pieces (approximately 1 cm3) were excised in the transition area between healthy and discolored wood. After surface sterilization (10 s in 70% ethanol + 90 s in NaOCl), the pieces were air dried for 1 min in a safety cabinet, cut into smaller pieces, and placed on media. The fungus was isolated on potato dextrose agar (PDA) and water agar (WA). On PDA, the cultures were tomentose, light orange, and grew slowly (21 mm mean colony diameter after 2 weeks at room temperature). Typical morphological features of C. fraxinea developed in culture. Brownish phialides (14.8 to 30.0 [19.5] × 2.5 to 5.0 [4.1] μm, n = 50) first appeared in the center of the colonies on the agar plugs that had been transferred. The agar plugs were 21 days old when phialides were observed. Abundant sporulation occurred 3 days later. Conidia (phialospores) extruded apically from the phialides and formed droplets. Conidia measured 2.1 to 4.0 (3.0) × 1.4 to 1.9 (1.7) μm (n = 50). The first-formed conidia from each phialide were different in size and shape from the rest by being longer (6 μm, n = 10) and more narrow in the end that first appeared at the opening of the phialide. Internal transcribed spacer sequencing confirmed that the morphological identification was correct (Accession No. EU848544 in GenBank). A pathogenicity test was carried out in June of 2008 by carefully removing one leaf per plant on 10 to 25 cm high F. excelsior trees (18 trees) and placing agar plugs from a 31-day-old C. fraxinea culture (isolate number 10636) on the leaf scars and covering with Parafilm. After 46 days, isolations were carried out as described above from discolored wood that had developed underneath necrotic lesions in the bark and subsequently caused wilting of leaves. All the inoculated plants showed symptoms, and C. fraxinea was successfully reisolated. No symptoms were seen on uninoculated control plants (eight trees) that had received the same treatment except that sterile PDA agar plugs had been used.

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To identify differentially expressed genes of the white-rot fungus Heterobasidion parviporum subtractive cDNA libraries were constructed using suppressive subtraction hybridization (SSH) technique with RNA extracted from an advanced stage of decay area and from colonization front next to the reaction zone of the stem of a mature Norway spruce trees. Besides cytochrome P450s and proteins with unknown function, the SSH libraries constructed contained genes involved in basic cellular processes, andcell wall degradation. To examine the role of selected candidate genes three trees, showing a variable degree of wood decay, were used for real-time RT-PCR profiling of candidate genes. In the decay transition areas the study revealed activity centers that showed remarkable similarity in the transcript profiles of monitored genes.

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The genome sequence of the conifer rot root pathogen Heterobasidion annosum was generated at JGI with 8.23 X coverage. The nuclear genome assembles in 39 scaffolds of total 33.7 Mbp estimated to cover 98.1% of the complete genome. We predicted 12,270 genes with an average length of 1,617 bp and exon number and length of 5.54 and 250 bp respectively. About 50% (5999) of the predicted genes could be validated by EST support with the 40,807 EST´s generated with in the project. The genome has a GC content of 52.0% and very little repetitive sequences with 2,895 SSR per mega base. The physical genome is congruent with the genetic linkage map, and most of the linkage groups have been possible to anchor to the 18 largest scaffolds.

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Clonal variation towards resistance has been observed in Norway spruce Heterobasidion annosum s.l. (H.a). H.a. is the main cause of root rot and has a severe economic impact on an economically important conifer tree species. Annual financial losses are in the hundreds of millions of Euros annually. Less susceptible clones appear to have an efficient system of recognizing the pathogen and initiating early defense signalling events. Active defense responses can be started locally and transmitted systemically. This work focus on the expression both spatially (systemically) and temporally in this pathosystem. Two-year-old, somatic saplings of the Norway spruce clone were challenged with H.a., wounded, methyl jasmonate painted and compared to untreated controls and ninety plants were used for the experiment. Stem samples were collected at 1, 3, 6 and 13 days post inoculation (d.p.i). The stem of the saplings were divided into sections along its length and the bark and wood separated from each other at time of collection. In order to see local response an area of 1cm including the site of inoculation was collected, while the spatial (systemic) response was assessed in sections collected at distances of 3 and 6cm away from the site of inoculation. The separated bark and wood were analysed for differential gene expression by qRT-PCR, and the results from peroxidases (PaPX3 and PaPX2) and a chitinase (PaChi4) are presented. Both local and systemic up- and down-regulation were observed at the transcriptional level in both bark and wood, up to 2000 fold local increase in expression was observed for PaChi4.

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Due to the great economic losses caused by the root and butt-rot pathogen Heterobasidion annosum, development of efficient control measures is warranted. H. annosum a necrotroph colonize the Norway spruce from inside and is responsible for 100s of millions of Euros losses annually. Considerable clonal variation has been recorded for Norway spruce in resistance towards H. annosum, but the defence mechanisms contributing to host resistance against both necrotrophic and biotrophic fungi remain poorly understood. The recent genome sequencing of Populus has made the genus a model to facilitate tree genetics. Genome-wide transcript profiling of Populus tremula upon pathogen attack will now be used, and homologues of Norway spruce genes to defence genes up-regulated in Populus will be identified. Two aspen clones (23 and 72) from the SwAsp collection (Luquez 2007) were used in the present study. Plants were propagated from tissue culture and kept in greenhouse under un-manipulated conditions. To study the host defence mechanisms, the rust (Melampsora magnusiana Wagner) and a bluestain fungus were used as a biotrophic and necrotrophic fungus respectively. Melampsora spores solution was applied to the underside of the leaf. To control for sectoriality six leaves were infected on each plant. To ensure high humidity and avoid cross contamination, plastic bags were wrapped around infected leaves. Leaves above infected leaves (10, 9, and 8) were harvested respectively 1, 3 and 14 days after inoculation. Initial results from microarray data indicate a clear separation between two Aspen clone (23 and 72) lines. For line 23 the response to biotroph and necrotroph seems to be similar. Whereas the response for line 72 is divergent for the treatments as they go in opposite direction. The controls show that there is an initial difference in the 2 lines (controls are separated). What are the genes that make biotrohic and necrotrophic treatment of 72 look so different will be worked out from microarray data. Differential expression of defense genes in biotrohic and necrotrophic treatment will be verified further with quantitative real time PCR. Chemical analysis of Aspen leaves gave less phenolic compounds as plants were kept in greenhouse. HPLC will be carried out after reaching some conclusion from microarray data analysis.