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.
2006
Abstract
When conifers such as Picea abies Karst. (Norway spruce) are attacked by insects or pathogens, they often respond by producing increased quantities of terpenoid oleoresin. This response can be mimicked in young P. abies seedlings by treatment with methyl jasmonate (MJ). In this study, we determined the effects of MJ on terpenoids and other chemical defenses of mature P. abies, and investigated whether this treatment protected trees against attack by the blue-stain fungus Ceratocystis polonica (Siem.) C. Moreau, the most important fungal associate of the spruce bark beetle Ips typo-graphus L. Methyljasmonate treatment induced the formation of traumatic resin ducts in the developing xylem, enhanced resin flow and stimulated increased accumulation of monoterpenes, sesquiterpenes and diterpene resin acids. However, only minor changes were detected in terpene composition in response to MJ treatment and no changes in soluble phenolic concentration were measured. There was much variability in the timing and degree of response to MJ among clones. The observed chemical and anatomical changes in response to MJ treatment were correlated with increased resistance to C. polonica, suggesting that terpenoid oleoresin may function in defense against this pathogen.
Abstract
Detailed analyses of thresholded ecological interactions can improve our understanding of the transition from aperiodic to periodic dynamics. We develop a threshold model of the population dynamics of outbreaking bark beetle populations that alternate between non-epidemic and epidemic behavior. The model involves accumulation of resources during low-density periods and depletion during outbreaks. The transition between the two regimes is caused by disturbance events in the form of major tree felling by wind. The model is analyzed with particular reference to the population dynamics of the spruce bark beetle (Ips typographus) in Scandinavia for which a comprehensive literature allows full parameterization. The fairly constant outbreak lengths and the highly variable waiting time between outbreaks that are seen in the historical records of this species agree well with the predictions of the model. The thresholded resource-depletion dynamics result in substantial variation in the degree of periodicity between stochastic realizations. The completely aperiodic tree colonizations are partly predictable when the timing of the irregular windfall events are known. However, the predictability of inter-outbreak periods is low due to the large variation of cases falling most frequently in the middle between the extremes of purely nonperiodic (erratic) and periodic (cyclic) fluctuations.
Abstract
No abstract has been registered
Abstract
Pulpwood has been imported to Norway since the beginning of the 20th century. However, exotic plant species hitchhiking with pulpwood were not observed before c.1985. Prior to this the imported timber was debarked, and the chances that diaspores would have attached to a debarked log (compared to a log with bark) are very small.A greenhouse germination experiment based on 385 dm2 of sifted bark from the holds of nine Estonian pulpwood ships yielded 3187 seeds of 201 species of vascular plants, few of which were typical of coniferous forests. Approximately 39% of the hitchhiking seeds did not germinate until after a period of cold treatment.Most of the species germinated in low densities, and those occurring in greater numbers are common and widespread in Norway. Six species were new to Norway: Agrostis clavata, Androsace filiformis, Bidens radiata, Carex montana, Melica picta, and Ranunculus cassubicus.During the last 20 years, pulpwood has been imported to Norway from many countries around the world, e.g. Russia, Scotland, Canada, and Zaire. While the present data do not indicate any immediate threat from aggressively invasive exotics, in order to avoid the introduction of non-native species and reduce the potential for biological invasion, timber should ideally be debarked prior to importation.
Authors
Guro BrodalAbstract
A survey of the loose smut frequencies in certified barley seed lots in Norway during 1997"2002 showed that the disease has become more prevalent and has occurred at higher infection frequencies in recent years. Laboratory analyses (embryo method) of barley seeds harvested in 2001 and 2002, including both certified and farm saved seed, showed a large number of infected seed lots with higher than expected infection frequencies. One lot of farm saved seed (cv. Otira) from 2002 had 32% seed infection. Unexpectedly high loose smut infection frequencies recorded in fields sown with carboxin treated barley seed suggest a reduced effectiveness of the fungicide. A seed treatment experiment was conducted in 2002 using both greenhouse and field trials with two infected seed lots (cv. Otira with 14.4% and cv. Fager with 6.9% infected seeds) to evaluate and compare the effect of Fungazil C (carboxin + imazalil) and Premis Robust (triticonazol + imazalil) against loose smut. Fungazil C at normal rates reduced loose smut frequencies by approximately 50% or less. At twice the normal rate, loose smut symptoms were reduced by 60-80%. Premis Robust showed more effective loose smut control, but did not confer complete control.
Abstract
No abstract has been registered
Abstract
Twenty-five tree species were recorded as hosts for five European Armillaria species in studies on forest ecosystems in Serbia. Armillaria was most frequently isolated from the conifers Picea abies and Abies alba and from the deciduous trees Fagus moesiaca and Quercus petraea. A. mellea and A. gallica coexisted in hardwood forests in northern and central parts of Serbia, while A. ostoyae and A. cepistipes were mostly present in coniferous forests in the southern mountain region of Serbia. The distribution depended on the Armillaria species, altitude, and the forest type.
Abstract
To identify chemical resistant markers induced by fungal or mechanical injury, young trees of Scots pine (Pinus sylvestris) were subjected to inoculations of blue stain fungi associated with the pine shoot beetles Tomicus piniperda and T. minor. Among the 20 trees selected for chemical analyses, 16 were divided into four groups: one as control and three were pretreated by wounding only, or by inoculation with either the blue stain fungus Leptographium wingfieldii or Ophiostoma canum.Four wk after pretreatment, all 16 pretreated trees were mass-inoculated with L. wingfieldii. The absolute and relative amounts, as well as the enantiomeric compositions of monoterpene hydrocarbons in the phloem, were determined via a small sample of the phloem before and after the pretreatment and mass inoculation, by using two-dimensional gas chromatography (2D GC) and GC-mass spectrometry (MS).After mass inoculation, the absolute amounts of most of the monoterpenes decreased in the phloem sampled 20 cm from the fungal infection, and were higher in the phloem sampled within the infected reaction zone.The relative amounts of both ()--pinene and ()-limonene increased in phloem samples taken 20 cm above the fungal inoculation in the preinoculated trees compared with phloem sampled from the remaining four control trees. The enantiomeric compositions of -pinene and limonene changed, after fungal growth, at defined distances from the inoculation site: the proportion of the ()-enantiomers was highest in the phloem sampled 20 cm from the fungal inoculation.Four wk after pretreatment, monoterpene production in the phloem at the site of inoculation was more enhanced by L. wingfieldii than by O. canum. However, the different virulence levels of the fungi did not affect the enantiomeric composition of the monoterpenes. The biosynthesis of monoterpene enantiomers is discussed in relation to induced pathogen resistance.
Abstract
No abstract has been registered
Abstract
No abstract has been registered