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 Nadeem Yaqoob Benedicte Riber Albrectsen Halvor SolheimAbstract
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.
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.
Authors
Isabella Børja Jan Svtlík Toril Drabløs Eldhuset Holger Lange Frank Newell Kidder Douglas Lawrence GodboldAbstract
No abstract has been registered
Authors
Carl Gunnar Fossdal Ari M. Hietala Igor A. Yakovlev Gustav Vaaje-Kolstad Emil Stefaczyk Halvor SolheimAbstract
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.
Authors
Venche TalgøAbstract
No abstract has been registered
Authors
Venche TalgøAbstract
No abstract has been registered
Authors
Guro BrodalAbstract
Sydowia polyspora was found to be seed borne on true fir (Abies spp.) where it is associated with two serious diseases; current season needle necrosis (CSNN) and Sclerophoma shoot dieback [1]. To our knowledge, S. polyspora was previously only reported to be seed borne on Scots pine (Pinus sylvestris) [3]. In 2009, we discovered S. polyspora on Norway spruce (Picea abies) seedlings from germination tests at the Norwegian Forest Seed Center. This indicated that S. polyspora also was seed borne on spruce. Based on this, we wanted to investigate how widespread S. polyspora was on conifer seeds. In 2010, we tested 44 seed lots from 8 genera. S. polyspora was isolates from seeds from the following genera; Abies, Larix, Picea, Pinus, Pseudotsuga, Thuja, and Tsuga. Interestingly, they are the exact same genera that Funk [2] reported S. polyspora from on diseased foliage and shoots. We found S. polyspora on Norway spruce harvested in 1970, thus, the fungus may survive for decades in seed lots. In Norway, Sclerophoma shoot dieback has been found on Norway spruce in Christmas tree fields. Fungal species from a number of other genera were also detected in the seed test, but here we only report S. polyspora.
Authors
Guro BrodalAbstract
No abstract has been registered
Authors
Arne StensvandAbstract
No abstract has been registered
Abstract
No abstract has been registered