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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.

2006

Sammendrag

Bark beetles and associated phytopathogenic fungi elicit defence responses in conifers that may interfere with beetle establishment and development. Norway spruce is serving as a useful model species for studies of induced defences elicited by beetle attacks, fungal inoculation, and treatment with chemical elicitors.When trees are pretreated with a sublethal dose of fungal inoculations or with the phytohormone methyl jasmonate they become much more resistant to subsequent bark beetle attacks or artificial mass inoculations with fungi. This induced disease resistance follows dose-response dynamics, is nonspecific with respect to the pretreatment organism, appears to be nonsystemic, takes weeks rather than days to become activated, and can also be activated by mechanical wounding alone.Application of methyl jasmonate to Norway spruce stems induces a massive increase in terpene levels and external resin flow on the stem, whereas no increase is observed in soluble phenolics. Methyl jasmonate-application also leads to significantly less bark beetle colonization, with shorter parental galleries and fewer eggs laid in treated bark. There were also reductions in the number of beetles produced and the mean dry weight per beetle in methyl jasmonate-treated bark. Furthermore, fewer beetles were attracted to conspecifics tunneling in MJ-treated bark.The exact mechanisms responsible for induced resistance in Norway spruce and other conifers have not been determined, but inducible anatomical defense responses such as changes in polyphenol-containing parenchyma cells (PP cells) in the phloem and induction of traumatic resin duct formation in the sapwood seem to play an important role.

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Sammendrag

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.

Sammendrag

The pine wood nematode, Bursaphelenchus xylophilus, which is indigenous to North America, was introduced to Asia in the early 1900 and now causes severe damage to susceptible pine species in Japan, China, Korea and Taiwan. B. xylophilus was included in the A1 list of quarantine organisms by EPPO (European Plant Protection Organization) in 1985. B. xylophilus was reported for the first time in Europe in Portugal in 1999. There are more than 50 described species within the genus Bursaphelenchus worldwide, that are associated with coniferous and deciduous trees and spread by insect vectors. Within this genus is a group of morphologically very similar species; B. xylophilus, B. mucronatus, B. fraudulentus, B. kolymensis, B. conicaudatus and B. luxuriosae. This group of species is often referred to as the "B. xylophilus group". Due to the morphological similarity of the species, identification of Bursaphelenchus species in the B. xylophilus group is difficult. The common method of molecular identification for separating species within the B. xylophilus group is the use of ITS-RFLP (Hoyer et al. 1998). We have developed a multiplex polymerase chain reaction (PCR) method with specific primers, and the primers amplified product were 740, 340 and 300 bp for B. xylophilus, B. fraudulentus and B. mucronatus respectively. No cross reactions on the three studied species were observed. In contrast to the previously described PCR-RFLP method, this new method allows detection not only on pure isolates, but also on crude nematode suspensions from wood samples, and it could be very useful for quarantine purposes. References Hoyer U, Burgermeister W, Braasch H 1998 Identification of Bursaphelenchus species (Nematoda, Aphelenchoididae) on the basis of amplified ribosomal DNA (ITS-RFLP). Nachrichtenbl. Deut. Pflanzenschutzd. 50:273-27. Mota M M, Braasch H, Bravo M A, Penas A C, Burgermeister W, Metge K, and Sousa E 1999. First report of Bursaphelenchus xylophilus in Portugal and in Europe. Nematology 1:727-734. Smith, I. M. 1985. Pests and disease problems in European forests. FAO Plant Prot. Bull. 33:159-164. Yi C, Park J, and Chang K 1989. Occurrence of pinewood nematode, Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle, and its vector, Monochamus alternatus Hope, in Korea. Pages 183-193 in: Proc. IUFRO Reg. Workshop For. Insect Pests and Tree Dis. in NE Asia. For. Prod. Res. Inst., Tsukuba, Japan.

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Sammendrag

We have made and partially sequenced two subtracted cDNA libraries, one representing genes predominantly expressed in a tree from an early-flushing family of Norway spruce (early-flushing library; EFL) and the second from a late flushing family (late flushing library; LFL), during 4 weeks before bud burst. In the EFL, expressed sequence tags (ESTs) encoding proteins of the photosynthetic apparatus and energy metabolism and proteins related to stress (abiotic and biotic) and senescence were abundant. ESTs encoding metallothionein-like and histone proteins as well as transcription factors were abundant in the LFL. We used quantitative real-time reverse transcription polymerase chain reaction to study the expression patterns of 25 chosen genes and observed that the highest levels of activity for most genes were present when plants were still ecodormant. The results indicate that the late flushing is not a result of a delay in gene activity, but is rather associated with an active transcriptional process. Accordingly, certain metabolic processes may be turned on in order to prevent premature flushing. We discuss the putative role of the studied genes in regulation of bud burst timing. Among the candidate genes found, the most interesting ones were the DNA-binding proteins, water-stress- related genes and metallothioneins. Expression patterns of some genes involved in chemical modification of DNA and histones indicate that epigenetic factors are involved in the timing of bud burst. In the obtained transcriptomes, we could not find genes commonly believed to be involved in dormancy and bud set regulation (PHY, CRY, ABI etc.) in angiosperm plants.

Sammendrag

Alternative metoder for å begrense skader forårsaket av gransnutebillen er svært aktuelle, både av hensyn til miljøet og fordi dagens kjemiske midler er på vei ut av bruk. I denne artikkelen fokusere vi på muligheten for å bruke et biologisk middel, nyttenematoder. Strategien med bruk av nyttenematoder går ut på å redusere produksjonen av nye gransnutebiller ved å drepe så mange larver som mulig i stubbene hvor de lever.