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.
2011
Forfattere
Inger Martinussen Abdelhameed Elameen Håvard Eikemo Monica Skogen Jahn Davik S. Fitwi Sonja Klemsdal May Bente BrurbergSammendrag
Rotstokkråte i jordbær ble første gang rapportert i Norge i 1992 og siden er den blitt funnet på mer enn 100 steder over hele landet. Sykdommen forårsakes av Phytophthora cactorum og karakteriseres ved at unge blader visner raskt og hele planten visner i løpet av noen dager. I løpet av en sesong kan opptil 40 % av plantene dø. P. cactorum smitter plantene gjennom rothårene ved hjelp av svermesporer (zoosporer). Sykdommen starter oftest i fuktige områder av et felt siden sporene trenger vann for å bevege seg. Når en først har fått smitten i jorda er det vanskelig å bli kvitt den siden P. cactorum danner hvilesporer som kan overleve i flere år. Ulike jordbærsorter har ulik grad av mottakelighet for sykdommen. De mest brukte kommersielle sortene er dessverre mottakelige for sykdommen. Resistensegenskaper kan styres av ett eller flere gener og man kan derfor foredle fram resistente sorter. Tradisjonell foredling er tidkrevende og overføringa av resistens til en mottakelig sort vil kreve gjentatte tilbakekrysninger slik at man ikke mister alle de positive egenskapene til denne sorten. Ved å utvikle genetiske kart med markører for resistens kan man teste planter raskere og slik komme raskere fram til en resistent sort. Kunnskap om hvor mange resistensgener som er involvert i kampen mot skadegjøreren, når disse blir slått på og hvilke proteiner disse lager er også viktig. Når en skadegjører angriper en plante lager den bl.a. proteiner som bryter ned plantecelleveggen og svekker plantens immunforsvar. Planten på sin side lager resistensproteiner som gjenkjenner proteinene laget av skadegjøreren. Denne gjenkjennelsen setter i gang en forsvarsrespons hos planten. Resistensproteinene kodes for av resistensgener (R-gener). De fleste kjente R-genene inneholder en kort bestemt nukleotidsekvens. Dette fellestrekket gjør jakten på resistensgener enklere. I jakten på resistensgener i jordbær har vi valgt å arbeide med markjordbær (Fragaria vesca) istedenfor kommersielle jordbær (Fragaria x ananassa Duch.). Markjordbær er diploid og egner seg derfor godt for molekylærbiologiske studier. For å isolere R-gener og studere hvordan de ble uttrykt ble en mottakelig kultivar og en resistent kultivar smittet med zoosporer. Vevsprøver ble høstet i en tidsserie fra tid 0 (kontroll før smitting) til maksimum 8 dager etter smitting. Resultatet så langt viser at vi har isolert fragmenter fra mange ulike resistensgener og at disse blir uttrykt gjennom hele tidsrommet fra smitting til 8 dager etterpå.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
May Bente BrurbergSammendrag
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Sammendrag
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Sammendrag
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Sammendrag
We treated Norway spruce (Picea abies) stems with methyl jasmonate (MeJA) to determine possible quantitative and qualitative eVects of induced tree defenses on pheromone emission by the spruce bark beetle Ips typographus. We measured the amounts of 2-methyl-3-buten-2-ol and (S)-cis-verbenol, the two main components of the beetle’s aggregation pheromone, released from beetle entrance holes, along with phloem terpene content and beetle performance in MeJA-treated and untreated Norway spruce logs. As expected, phloem terpene levels were higher and beetle tunnel length was shorter (an indication of poor performance) in MeJA-treated logs relative to untreated logs. Parallel to the higher phloem terpene content and poorer beetle performance, beetles in MeJA-treated logs released signiWcantly less 2-methyl-3-buten-2-ol and (S)-cis-verbenol, and the ratio between the two pheromone components was signiWcantly altered. These results suggest that host resistance elicited by MeJA application reduces pheromone emission by I. typographus and alters the critical ratio between the two main pheromone components needed to elicit aggregation. The results also provide a mechanistic explanation for the reduced performance and attractivity observed in earlier studies when bark beetles colonize trees with elicited host defenses, and extend our understanding of the ecological functions of conifer resistance against bark beetles.
Forfattere
Axel Schmidt Raimund Nagel Trygve Krekling Erik Christiansen Jonathan Gershenzon Paal KrokeneSammendrag
Norway spruce (Picea abies) defends itself against herbivores and pathogens by formation of traumatic resin ducts filled with terpenoid-based oleoresin. An important group of enzymes in terpenoid biosynthesis are the short-chain isoprenyl diphosphate synthases which produce geranyl diphosphate (C10), farnesyl diphosphate (C15), and geranylgeranyl diphosphate (C20) as precursors of monoterpenes, sesquiterpenes, and diterpene resin acids, respectively. After treatment with methyl jasmonate (MJ) we investigated the expression of all isoprenyl diphosphate synthase genes characterized to date from Norway spruce and correlated this with formation of traumatic resin ducts and terpene accumulation. Formation of traumatic resin ducts correlated with higher amounts of monoterpenes, sesquiterpenes and diterpene resin acids and an upregulation of isoprenyl diphosphate synthase genes producing geranyl diphosphate or geranylgeranyl diphosphate. Among defense hormones, jasmonate and jasmonate-isoleucine conjugate accumulated to higher levels in trees with extensive traumatic resin duct formation, whereas salicylate did not. Jasmonate and ethylene are likely to both be involved in formation of traumatic resin ducts based on elevated transcripts of genes encoding lipoxygenase and 1-aminocyclopropane-1-carboxylic acid oxidase associated with resin duct formation. Other genes involved in defense signalling in other systems, mitogen-activated protein kinase3 and nonexpressor of pathogenesis-related gene1, were also associated with traumatic resin duct formation. These responses were detected not only at the site of MJ treatment, but also systemically up to 60 cm above the site of treatment on the trunk.
Forfattere
May Bente Brurberg Abdelhameed Elameen Vinh Hong Le Ragnhild Nærstad Arne Hermansen Ari Lehtinen Asko Hannukkala Bent Nielsen Jens Hansen Björn Andersson Jonoathan YuenSammendrag
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Forfattere
Roman Gebauer Daniel Volařík Josef Urban Isabella Børja Nina Elisabeth Nagy Toril Eldhuset Paal KrokeneSammendrag
Conifers and other trees are constantly adapting to changes in light conditions, water/nutrient supply and temperatures by physiological and morphological modifications of their foliage. However, the relationship between physiological processes and anatomical characteristics of foliage has been little explored in trees. In this study we evaluated needle structure and function in Norway spruce families exposed to different light conditions and transpiration regimes. We compared needle characteristics of sun-exposed and shaded current-year needles in a control plot and a thinned plot with 50% reduction in stand density. Whole-tree transpiration rates remained similar across plots, but increased transpiration of lower branches after thinning implies that sun-exposed needles in the thinned plot were subjected to higher water stress than sun-exposed needles in the control plot. In general, morphological and anatomical needle parameters increased with increasing tree height and light intensity. Needle width, needle cross-section area, needle stele area and needle flatness (the ratio of needle thickness to needle width) differed most between the upper and lower canopy. The parameters that were most sensitive to the altered needle water status of the upper canopy after thinning were needle thickness, needle flatness and percentage of stele area in needle area. These results show that studies comparing needle structure or function between tree species should consider not only tree height and light gradients, but also needle water status. Unaccounted for differences in needle water status may have contributed to the variable relationship between needle structure and irradiance that has been observed among conifers.
Forfattere
Abdelhameed Elameen Arild Larsen Sonja Klemsdal Siri Fjellheim Leif Sundheim Susan Msolla Esther Masumba Odd Arne RognliSammendrag
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