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.
2004
Forfattere
O. NordalSammendrag
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Forfattere
Tore SkrøppaSammendrag
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Forfattere
Nina Elisabeth Nagy Carl Gunnar Fossdal Paal Krokene Trygve Krekling Anders Lönneberg Anders Lønneborg Halvor SolheimSammendrag
Polyphenolic parenchyma cells (PP cells) in Norway spruce (Picea abies (L.) Karst.) stem phloem play important roles in constitutive and inducible defenses. To determine whether anatomical and molecular changes in PP cells are correlated with tree resistance, we infected two Norway spruce clones with the pathogenic fungus Ceratocystis polonica (Siem.) C. Moreau. The fungus induced significantly different lesion lengths in the two clones, indicating that one clone was more resistant to the fungus (short lesions) than the other (long lesions). After infection, the cross-sectional area of PP cells and their vacuolar polyphenol bodies increased in the three most recent annual rings of PP cells in both clones. The more resistant clone had larger PP cells with denser polyphenol bodies than the less resistant clone, whereas the less resistant clone accumulated relatively more polyphenols after infection. Compared with the less resistant clone, the more resistant clone contained higher starch concentrations before infection that were reduced more quickly after infection before returning to original values. Low transcript levels of chalcone synthase were detected in uninfected tissues of both clones, but the levels increased dramatically after infection. Transcript levels were higher and peaked 6 days earlier in the more resistant clone than in the less resistant clone. The activity of at least one highly basic peroxidase isoform was greatly enhanced after infection, and this increase occurred earlier in the more resistant clone.
Forfattere
J.W. Hudgins Erik Christiansen Vincent R. FranceschiSammendrag
Conifers have evolved constitutive and inducible defense mechanisms to help in both wound healing and defense against attack by bark beetles and other organisms. These defenses include oleoresin, phenolics, and static structures in secondary phloem, such as lignified cells and calcium oxalate crystals, that create physical barriers. We used a phylogenetic approach to investigate the defense anatomy of conifer stems of 13 species from five families following treatment with methyl jasmonate (MJ), a compound that induces defense responses in stems of several Pinaceae species.Methyl jasmonate induced a response similar to wounding except that the response was not accompanied by lesion formation, necrosis or a hypersensitive response. In the Pinaceae species studied, MJ induced polyphenolic parenchyma (PP) cell activation and xylem traumatic resin duct (TD) formation. Members of the Taxodiaceae, which are not known to produce large quantities of resin, showed massive xylem TD formation and surface resinosis following MJ treatment.Treatment with MJ caused members of the Araucariaceae and Cupressaceae to form axial phloem resin ducts but not xylem ducts, whereas Podocarpaceae species showed no induction of resin-producing structures. All species treated with MJ showed phenolic deposition in PP cells, and early lignification of phloem fibers was observed in most of the non-Pinaceae species.We conclude that, although evolution of resin-producing structures occurred independently in conifer lineages, MJ seems to induce resin production regardless of tissue location, as well as inducing deposition of phenolic compounds. Co-evolution of conifer defensive strategies and bark beetle pests is discussed.
Forfattere
Gro Skøien Johannessen Randi Berland Frøseth Liv Solemdal Jorunn Jarp Yngvild Wasteson Liv Marit RørvikSammendrag
Aim: To investigate the bacteriological quality, and the occurrence of selected pathogenic bacteria from organically grown Iceberg lettuce fertilized with bovine manure in the form of compost, firm manure and slurry in a 2-year field trial. Methods and Results: Samples of soil, fertilizer, fertilized soil, seedlings and lettuce were analysed for aerobic plate counts (APC), thermotolerant coliform bacteria (TCB), Escherichia coli, E. coli O157:H7, Salmonella spp. and Listeria monocytogenes. No difference in bacteriological quality could be shown in lettuce at harvest, however, APC varied significantly from year to year in the study. The various treatments gave significantly different APC and numbers of TCB isolated from fertilized soil. Escherichia coli O157:H7 was isolated from firm manure and slurry, and soils fertilized with the respective fertilizers the second year, but were not recovered from the lettuce. Conclusions: No difference in bacteriological quality could be detected in lettuce at harvest after application of various types of manure-based fertilizers grown under Norwegian conditions. Significance and Impact of the Study: The results may indicate that the use of manure does not have considerable influence on the bacteriological quality of organic lettuce. However, others have suggested that there is a risk by using manure. There is a need for more research in the field.
Sammendrag
The searching efficiency of Encarsia formosa Gahan (Hymenoptera: Aphelinidae) and the control efficiency of E. formosa and Macrolophus caliginosus Wagner (Hemiptera: Miridae) were studied on the hairy poinsettia (Euphorbia pulcherrima Willd.ex Koltz.) cultivar `Lilo" (2030 hairs/cm2, hair length 18.0 mm) and the less hairy cultivar `Sonora" (449 hairs/cm2, hair length 11.8 mm) at 18 - 21oC, in order to evaluate their potential as biological control agents in greenhouse poinsettia production. Inexperienced (less than 24 hours old) E. formosa (EN-STRIP, Koppert B.V.) were observed individually for 7 minutes on poinsettia leaves without whiteflies, using the automatic video tracking system for behavioural studies, EthoVision Color Pro. Their walking speed, walking activity and walking pattern were not influenced by the leaf hairiness. When the temperature was lowered from 20 to 18oC, the mean walking speed decreased by 15%, from 0.52 to 0.44 mm/sec on `Lilo" and from 0.51 to 0.43 mm/sec on `Sonora". The mean walking activity was 89% on `Lilo" and 88% on `Sonora" at 20oC, and was decreased by 6 and 13%, respectively, at 18oC. Temperature did not influence the straightness of the walking path. The control efficiency of E. formosa and M. caliginosus (MIRICAL, Koppert B.V.) was studied on `Lilo" and `Sonora" infested with Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) B biotype in 2 cage experiments at 21oC, and is currently being studied at lower temperatures. E. formosa was introduced when the first whitefly nymphs had reached the 3rd instar, and was released weekly 3 times at a total rate of 4.2 parasitoids/adult whitefly. M. caliginosus was introduced when the first whitefly nymphs had reached the 1st instar, and was released every 2 weeks 3 times at a total rate of 1.5 predatory bugs/adult whitefly. One tobacco plant (Nicotiana tabacum `Xanthi") was placed in each of the cages where M. caliginosus was released. The control efficiency (measured as % reduction of number of immature whiteflies compared to the control when the plants were ready for sale) ranged from 63 to 93% for E. formosa and from 64 to 82% for M. caliginosus. E. formosa gave slightly better control than M. caliginosus on `Sonora", and in one of the experiments with `Lilo". The parasitoids were more efficient, and the parasitism was higher, on `Sonora" than on `Lilo". No damage to green leaves or bracts has been observed on the plants where M. caliginosus was released.
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