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.

2019

Sammendrag

Aims Bacterial decays of onion bulbs have serious economic consequences for growers, but the aetiologies of these diseases are often unclear. We aimed to determine the role of Rahnella, which we commonly isolated from bulbs in the United States and Norway, in onion disease. Methods and Results Isolated bacteria were identified by sequencing of housekeeping genes and/or fatty acid methyl ester analysis. A subset of Rahnella spp. strains was also assessed by multilocus sequence analysis (MLSA); most onion strains belonged to two clades that appear closely related to R. aquatilis. All tested strains from both countries caused mild symptoms in onion bulbs but not leaves. Polymerase chain reaction primers were designed and tested against strains from known species of Rahnella. Amplicons were produced from strains of R. aquatilis, R. victoriana, R. variigena, R. inusitata and R. bruchi, and from one of the two strains of R. woolbedingensis. Conclusions Based on binational testing, strains of Rahnella are commonly associated with onions, and they are capable of causing mild symptoms in bulbs. Significance and Impact of the Study While Rahnella strains are commonly found within field‐grown onions and they are able to cause mild symptoms, the economic impact of Rahnella‐associated symptoms remains unclear.

Sammendrag

I 2018 vart totalt 130 prøvar av jord frå importerte grøntanleggsplanter analyserte for nematodar og Phytophthora spp. i OK-programmet «Nematoder og Phytophthora spp. i jord på importerte planter”. Prøvane vart tatt ut av inspektørar ved regionkontora til Mattilsyner. Større tre til utplanting hadde førsteprioritet. Her rapporterar vi Phytophthora-delen av OK-programmet. I 35 % av prøvane vart det totalt funne 14 Phytophthora-artar fordelt på fleire opphavsland; Polen, Tyskland, Nederland, Belgia, Italia og våre to naboland Sverige og Danmark. Ingen av Phytophthora-artane var karanteneorganismar, men fleire av dei gjer i dag skade i både grøntanlegg og norsk natur, til dømes Phytophthora cambivora og P. plurivora på bøk (Fagus sylvatica). Kartleggingsprogrammet skal fylgjast opp i 2019.

Sammendrag

I 2011 vart symptom på angrep av Phytophthora på bøk (Fagus sylvatica) i bøkeskogen i Larvik oppdaga for fyrste gong. Skadegjeraren vart identifisert til Phytophthora cambivora. I tillegg vart det funne andre Phytophthora-artar i jord/vatn i og nær bøkeskogen. Dette førte til ei grundig kartlegging av situasjonen og Phytophthora vart tatt omsyn til i ein forvaltningsplan for bøkeskogen frå Fylkesmannen i Vestfold i 2013. I denne planen vart det stadfesta at Phytophthora-situasjonen skulle fylgjast opp med ny kartlegging om 5 år, noko som vart gjennomført i 2018 og presentert i denne rapporten. Vi fann fleire tre som hadde vorte sjuke sidan førre kartlegging, men utviklinga har ikkje gått så raskt som vi frykta. Også andre skadegjerarar det bør tast omsyn til ved skjøtsel av bøkeskogen vert omtala.

Til dokument

Sammendrag

Four species of the destructive forest pathogen Heterobasidion annosum sensu lato (s.l.) are present in Europe: H. annosum sensu stricto (s.s.), H. abietinum and H. parviporum are native species, while H. irregulare is a non‐native invasive species currently reported only in Italy, yet recommended for regulation throughout Europe. In this study, real‐time PCR detection tests were developed for each of the four species, which can be used simultaneously or individually thanks to probes labelled with species‐specific fluorescent dyes. The different performance criteria of each assay were evaluated, and it was determined that they were theoretically capable of detecting amounts of DNA corresponding to 311, 29 and 29 cell nuclei in H. annosum s.s., H. irregulare and H. parviporum, respectively. The specificity of each assay was assessed with a wide set of strains. Real‐time PCR tests successfully detected Heterobasidion species from 36 fruiting bodies taken from the forest, as well as from artificially inoculated or naturally infected wood samples. The multiplex real‐time PCR assays developed in this study could have practical applications both in forest management and in phytosanitary monitoring.

Til dokument

Sammendrag

Several studies have looked at how individual environmental factors influence needle morphology in conifer trees, but interacting effects between drought and canopy position have received little attention. In this study, we characterized morphological responses to experimentally induced drought stress in sun exposed and shaded current-year Norway spruce needles. In the drought plot trees were suffering mild drought stress, with an average soil water potential at 50 cm depth of -0.4 MPa. In general, morphological needle traits had greater values in sun needles in the upper canopy than in shaded needles in the lower canopy. Needle morphology 15 months after the onset of drought was determined by canopy position, as only sun needle morphology was affected by drought. Thus, canopy position was a stronger morphogenic factor determining needle structure than was water availability. The largest influence of mild drought was observed for needle length, projected needle area and total needle area, which all were reduced by ~27% relative to control trees. Needle thickness and needle width showed contrasting sensitivity to drought, as drought only affected needle thickness (10% reduction). Needle dry mass, leaf mass per area and needle density were not affected 15 months after the onset of mild drought. Our results highlight the importance of considering canopy position as well as water availability when comparing needle structure or function between conifer species. More knowledge about how different canopy parts of Norway spruce adapt to drought is important to understand forest productivity under changing environmental conditions.

Til dokument

Sammendrag

Standardized tools are needed to identify and prioritize the most harmful non-native species (NNS). A plethora of assessment protocols have been developed to evaluate the current and potential impacts of non-native species, but consistency among them has received limited attention. To estimate the consistency across impact assessment protocols, 89 specialists in biological invasions used 11 protocols to screen 57 NNS (2614 assessments). We tested if the consistency in the impact scoring across assessors, quantified as the coefficient of variation (CV), was dependent on the characteristics of the protocol, the taxonomic group and the expertise of the assessor. Mean CV across assessors was 40%, with a maximum of 223%. CV was lower for protocols with a low number of score levels, which demanded high levels of expertise, and when the assessors had greater expertise on the assessed species. The similarity among protocols with respect to the final scores was higher when the protocols considered the same impact types. We conclude that all protocols led to considerable inconsistency among assessors. In order to improve consistency, we highlight the importance of selecting assessors with high expertise, providing clear guidelines and adequate training but also deriving final decisions collaboratively by consensus.

Sammendrag

Infections of Neonectria ditissima, the cause of European fruit tree canker, may be initiated during propagation. In a survey of 19 commercial apple orchards in southern Norway in the year of planting or the following year, the graft-union area of 15,270 trees was examined. The disease was found in 53% of the orchards, at a low incidence (<10%) with two exceptions (13 and 42%). Scion wood from mother trees with no, a few or several cankers were used to propagate trees that were surveyed for up to 38 months. In total 20 out of 1116 (1.8%) trees developed canker. The higher the number of cankers was on the mother trees, the higher was the number of trees developing canker after grafting. Infections developed on both cultivars (Discovery, Summerred) and all three rootstocks (Antonovka, B9, M9), but more so on grafted than T-budded trees, and more in 2015 than in 2014. When the scion wood was inoculated at the time of T-budding or grafting, disease development went faster and to a higher incidence on T-budded (94%) than on grafted trees (50%). Dipping the scion wood end in a spore suspension prior to grafting resulted in more infections than when a suspension droplet was placed on the bud and bark surface of the scion wood after grafting. The present investigation documents that scion wood may harbour inoculum of N. ditissima. Furthermore, infections may be initiated at time of propagation, and management practices of both scion wood production and nurseries should encounter that fact.