Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2016
Forfattere
R. Drenkhan Halvor Solheim A. Bogacheva T. Riit K. Adamson T. Drenkhan T. Maaten Ari HietalaSammendrag
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.
Forfattere
Ari HietalaSammendrag
Det er ikke registrert sammendrag
Forfattere
Ari HietalaSammendrag
Det er ikke registrert sammendrag
Forfattere
Ari HietalaSammendrag
Det er ikke registrert sammendrag
Sammendrag
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.
Sammendrag
In Europe, common ash (Fraxinus excelsior) is being decimated because of the invasive fungus Hymenoscyphus fraxineus. In its native range in Asia this ascomycete is considered a harmless leaf associate of F. mandshurica and F. chinensis subsp. rhynchophylla. Field observations from Europe suggest that there is speciesspecific variation in disease susceptibility among European and North American Fraxinus species, but a wider comparison at the genus level has been missing so far. We assessed disease symptoms and pathogen apothecium development in 17 Fraxinus species from Asia, Europe and North America exposed to high infection pressure in a Danish arboretum. We also tested their susceptibility to pathogen infection through controlled stem and leaf inoculations and subsequently assessed the level of pathogen DNA by a qPCR assay. The results suggested the presence of a phylogenetic signal in disease susceptibility where closely related Asian, European and North American species in section Fraxinus had relatively high levels of H. fraxineus DNA in the leaves and supported high production of apothecia. Leaves from some North American species also contained relatively high levels of H. fraxineus DNA, supported moderate production of apothecia and developed lesions—stating the need to avoid introduction of H. fraxineus to North America.
Forfattere
Ari HietalaSammendrag
Det er ikke registrert sammendrag
Forfattere
Isabella BørjaSammendrag
Det er ikke registrert sammendrag
Forfattere
Isabella BørjaSammendrag
Det er ikke registrert sammendrag
Forfattere
Isabella Børja Jan Svetlik Valeriy Nadezhdin Jan Čermák Sabine Rosner Nadezhda NadezhdinaSammendrag
Top dieback of Norway spruce (Picea abies), triggered by drought in 2004–2006, has been observed in Southeast Norway and trees died within four years after appearance of the first symptoms. The aim of our study was to use sap flux measurements as a diagnostic method for assessment of tree vitality. We used the heat field deformation method to monitor the sap flux density (SFD) in four pairs of healthy and declining trees in situ. To provide retrospective information on hydraulic performance of the trees we took samples for wood anatomical analysis. After felling the trees we used the modified differential translucence method (MDT) as a proxy for the SFD measurements. Healthy trees had three times higher SFD values as declining trees. In some healthy trees we detected decreasing SFD with time. The MDT method agreed with the SFD measurements. In conclusion, we detected sap flux dysfunction in declining trees and showed that the SFD reduction may occur during a short period, prior to occurrence of any visual symptoms. We suggest incorporating the SFD measurements into the repertoire of diagnostic tools in forest pathology.