Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2012
Authors
Carl Gunnar Fossdal Nina Elisabeth Nagy Ari Hietala Harald Kvaalen Rune Slimestad Steve Woodward Halvor SolheimAbstract
No abstract has been registered
Abstract
This chapter provides an overview of anatomical and ecological aspects of resin-based defences in pines and contrasts the defence strategy of pines with that of other conifers. The main constituents of conifer resin are mono- and diterpenes in about equal amounts, with smaller amounts of sesquiterpenes. Resin production and storage represent a great cost for the trees, and because resin is both chemically toxic and physically deterring to insects and pathogens it has long been considered an important defence mechanism in conifers. Preformed or constitutive resin structures are present in pines and all other members of the pine family, but are generally absent in non-Pinaceae species. Resin stored under pressure in constitutive ducts flows out when a tree is injured and helps trapping or repelling invading organisms and sealing the wound. Pines have constitutive resin ducts in needles, phloem and xylem. In the phloem and xylem constitutive resin ducts are oriented both radially (within the radial rays) and axially in the form of cortical resin ducts in the outer phloem and constitutive resin ducts in the xylem. Numerous connections between the radial resin ducts and the axial resin ducts in the xylem create a large inter-connected resin reservoir. In addition, so-called traumatic resin ducts can be induced axially in the xylem in response to wounding, insect attack or other biotic and abiotic stresses. Traumatic resin ducts may contribute to so-called acquired or systemic induced resistance that increases tree resistance to future attacks.
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Mohamed Abdelhalim Åshild Ergon Mallikarjuna Rao Kovi Anil Kunapareddy May Bente Brurberg Ingerd Skow Hofgaard Anne Marte Tronsmo Odd Arne RognliAbstract
No abstract has been registered
Authors
Åke Olson Andrea Aerts Fred Asiegbu Lassaad Belbahri Ourdia Bouzid Anders Broberg Björn Canback Pedro M. Coutinho Dan Cullen Kerstin Dalman Giuliana Deflorio Linda T.A. van Diepen Christophe Dunand Sébastien Duplessis Mikael Durling Paolo Gonthier Jane Grimwood Carl Gunnar Fossdal David Hansson Bernard Henrissat Ari Hietala Kajsa Himmelstrand Dirk Hoffmeister Nils Högberg Timothy Y. James Magnus Karlsson Annegret Kohler Ursula Kües Yong-Hwan Lee Yao-Cheng Lin Mårten Lind Erika Lindquist Vincent Lombard Susan Lucas Karl Lundén Emmanuelle Morin Claude Murat Jongsun Park Tommaso Raffaello Pierre Rouzé Asaf Salamov Jeremy Schmutz Halvor Solheim Jerry Ståhlberg Heriberto Vélëz Ronald P. de Vries Ad Wiebenga Steve Woodward Igor A. Yakovlev Matteo Garbelotto Francis Martin Igor V. Grigoriev Jan StenlidAbstract
• 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.
Authors
Igor A. Yakovlev Gustav Vaaje-Kolstad Ari Hietala Emil Stefanczyk Halvor Solheim Carl Gunnar FossdalAbstract
No abstract has been registered
Abstract
In South-east Norway, several scattered observations of reduced growth and dieback symptoms were observed over the last 20 years in 40-60 years old Norway spruce (Picea abies) trees. Typical symptoms start with yellowing in the top and subsequent dieback downwards from the top. These symptoms are often combined with bark beetle (Ips typographus), honey fungus (Armillaria spp.) infections, and a sudden decrease in diameter and height growth. After about 1-5 years, most of the symptomatic trees are dead.We selected 11 representative stands in six counties. In each stand all trees in ten 250 m2 plots were evaluated, in total about 4000 trees. In each of these 110 plots, one symptomatic and one non-symptomatic tree were investigated in more detail. We measured tree diameter, height, took increment cores and assessed crown condition, wounds, resin flow, stem cracks, bark beetle infection and Armillaria presence. In addition, internode lengths of the last 20 years were measured in two of the stands.Preliminary results of internode lengths and increment cores showed a sudden decrease of height and diameter growth in the symptomatic trees. Many of these trees had a secondary infection of bark beetles and Armillaria. Some years appear to be typical problem years for many of the trees. These years also correspond with summer drought, i.e. negative Palmer drought severity indexes which were estimated for each stand. In comparison, the non-symptomatic trees, growing close to the symptomatic ones, showed none or minor growth reductions and discolouration.Climate change and increased summer drought may worsen spruce dieback problems. Management adaptions are uncertain. We conclude that Norway spruce is sensitive to drought, which reduce the growth and weaken the health, and probably reduce the defence against secondary infections.
2011
Abstract
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.
Abstract
No abstract has been registered