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.
2008
Forfattere
Lars Tørres HavstadSammendrag
Konklusjonene i halmbehandlingsforsøkene i timotei og engsvingel er følgende: Flere av de prøvde halmbehandlingsmetodene kan være brukbare alternativ til halmfjerning. I praksis vil halmkutting ved tresking være det mest effektive og minst arbeidskrevende alternativet til å fjerne halmen. Ved en slik praksis bør stubbehøyden ved siste tresketid være så lav som mulig (helst under 10 cm). Alternativt : snitte lang stubb etter tresking. Halmen må spres jevnt utover enga. Viktig med skarpe kniver på halmkutteren.
Forfattere
Lars Tørres HavstadSammendrag
Fordrag om modningsforløp, riktig høstetid, innstilling av tresker ved frøavl av timotei. Se vedlegt pdf-fil av foredraget for mer info.
Forfattere
Lars Tørres HavstadSammendrag
I forsøk med utprøving av ulike metoder for behandling av dekkvekstens halm (vårhvete) i gjenlegg av rødkløverfrøeng, har kutting av halm med treskerens kutteutstyr vært avlingsmessig fullt på høyde med ruter hvor halmen har vært fjernet De høyeste frøavlingene, både når halmen var fjernet og når halmen var kuttet, ble høstet på rutene som var stubbet lavt (5-10 cm) ved tresking av dekkveksten. Når halmen ble kuttet ved lav stubbehøyde under treskinga, og halmen jevnt spredd på enga, var det i forsøkene ingen avlingsgevinst å hente ved å kjøre en ekstra omgang med halmsnitter etter tresking for ytterligere å snitte halm og stubb. I tilfeller hvor halmen er ujevnt fordelt og stubben av varierende høyde, kan det likevel være en fordel å benytte halmsnitteren for å jevne ut stubb og fordele halmen bedre etter høsting.
Forfattere
Erling FløistadSammendrag
Vi skaffer oss i gjennomsnitt mer enn én julestjerne hver. Til sammen kjøper vi hvert år ca 6 millioner julestjerner for å pynte til jul. Helt fram til 1980 ble det solgt flere julegleder enn julestjerner i Norge. I dag selges det 28 julestjerner for hver gang noen kjøper en juleglede. Hva det er som har gitt julestjerna denne populariteten? Potteplanten julestjernes historie er en fortelling om en plante og en bakterie som sammen gir oss den juleblomsten vi kjenner i dag. Men det er også en fortelling om fremsynte personer, bevisst markedsføring og jakten på "Annette Heggs hemmelighet".
Forfattere
David M. Gadoury Arne Stensvand Robert C. Seem Catherine Heidenreich Maria Herrero Mary Jean Welser Andrew Dobson Håvard Eikemo Belachew AsalfSammendrag
Cleistothecia on leaves of deciduous perennials are often dispersed before leaf fall to other substrates. In contrast, strawberry leaves remain attached during winter, and cleistothecia of Podosphaera macularis remained attached to these leaves. Release of overwintered ascospores was coincident with renewed plant growth, and pathogenicity of ascospores was confirmed. Upper and lower surfaces of emergent leaves were similarly susceptible, but upper surfaces were obscured by folding in emergent leaves. Emergent leaves exposed to airborne inoculum developed severe infection of the lower surface, but not the obscured upper surface. Emergent leaves acquired ontogenic resistance during unfolding, and the upper leaf surface thereby escaped infection. We found no evidence that the pathogen survives winters in New York, USA or Norway within crown tissue. Plants stripped of infected leaves remained mildew-free when forced after overwintering, while mildew colonies commonly developed on emergent leaves of plants not stripped of mildewed leaves. Unsprayed plots established using mildew-free plants either remained asymptomatic or developed only traces of powdery mildew during one growing season, even when located within 100 to 150 meters of severely diseased plots. In summary, our results suggest the following: (i) sanitation, use of disease-free plants, and eradicative treatments could contribute greatly to management of strawberry powdery mildew; (ii) cleistothecia represent a functional source of primary inoculum; and (iii) the common observation of higher mildew severity on lower leaf surfaces may reflect escape of the upper epidermis due to the combined effect of leaf folding and rapid acquisition of ontogenic resistance.
Sammendrag
Colletotrichum acutatum is the causal agent of anthracnose/bitter rot in cherry and apple in Norway. It is the most important fruit decay in sour cherry in the country and may give severe losses also in sweet cherry and apple. Single spore isolates frequently develops the ascigerous stage of the fungus (Glomerella acutata) in culture, but it has not yet been detected on apple or cherry plant material. We thus anticipate that the predominant inoculum source is conidia (formed in acervuli). The fungus overwinters in old infected fruits and fruit stalks, in bud shells and in wood of cherry and apple. Infected flowers and leaves may serve as additional inoculum for fruit infections during the growing season. If still attached to the tree, fruits and fruit stalks of sour cherry infected the previous year may produce inoculum of C. acutatum throughout the entire following season. Up to 80% of the fruit spurs on sweet cherry may have buds infected with C. acutatum in spring. Apple buds may also contain the fungus. More than 90% of the sweet cherry leaves may contain C. acutatum around harvest in heavily infected orchards. The entire leaf surface may be infected, but visible infections never appear. We frequently also find such asymptomatic leaf infections in apples. Most of the inoculum seems to be present on the fruit trees themselves. However, initial inoculum in newly planted, disease free plantings may come from older fruit trees, ornamentals and weeds in or in close vicinity to the orchards.
Forfattere
Arne Stensvand Heidi Udnes Aamot Gunn Mari Strømeng Venche Talgø Abdelhameed Elameen Jorunn Børve Sonja KlemsdalSammendrag
The ascigerous stage (formation of perithecia with viable ascospores) of Colletotrichum acutatum was recently reported to occur on fruits of highbush blueberry (Vaccinium corymbosum) in Norway. When 113 isolates of C. acutatum from various plant species were cultured on strawberry leaf agar, nine developed perithecia with viable ascospores. Four isolates originated from apple (Malus domestica) and one each from sweet cherry (Prunus avium), raspberry (Rubus idaeus), highbush blueberry (Vaccinium corymbosum), hollyberry cotoneaster (Cotoneaster bullatus), and northern dock (Rumex longifolius). Except from blueberry, we never detected the ascigerous stage on decaying fruits or any other parts of the above mentioned plant species. On potato dextrose agar, colour of the underside of the cultures forming perithecia varied from light grey-green to dark grey-green or dark brown-green. Colour of the upperside varied greatly, being dark grey-green, grey-brown, grey, and beige-pink, and only two of the isolates were beige-pink (the raspberry and blueberry isolates). Amplified fragment length polymorphism (AFLP) analysis of the isolates using six primer combinations resulted in 103 clear polymorphic bands. A dendrogram was constructed, and based on cluster analysis using genetic similarity, the isolates could be divided into several clusters. Eight of nine perithecia-forming isolates grouped together in the dendrogram, indicating genetical difference from other isolates. This was also supported by Principal Coordinate (PCO) analysis.
Sammendrag
Most fungicide applications targeting apple scab aim to control primary infections caused by ascospores and spraying is thereby linked to ascospore availability. We investigated the effect of pre bud break climatic conditions on seasonal patterns of ascospore release. Apple leaves bearing pseudothecia of Venturia inaequalis were overwintered at orchard sites in 8 countries for up to 3 years. Leaf samples were collected 2 to 5 weeks before bud break and again at bud break, air dried, and sent via airmail to Norway. The samples were stored at -18 ºC upon arrival until tested. Disks cut from each replicate leaf sample were incubated moist at 20 ºC to allow ascospore maturation but prevent discharge. Matured ascospores were induced to discharge twice a week and enumerated until the supply was exhausted. The proportion of ascospores ejected was fitted against degree day accumulation using logistic regression. The regression intercept (onset maturation), slope (maturation rate), as well as the absolute number of spores counted differed significantly (P < 0.001, P = 0.05, P < 0.001 respectively) among sites and sampling dates. There was a significant interaction between site and sampling date, indicating that climatic conditions prior to bud break differentially impacted the subsequent ascospore availability. Observed differences could perhaps be used to further refine previously described models of ascospore maturity.
Forfattere
Arne StensvandSammendrag
Black spot caused by Colletotrichum acutatum is occasionally found in strawberry fields in Norway. It was detected for the first time in 1999 and found in certified production in 2002. More than half of the certified nurseries, including the elite plant station, had symptomless infections of C. acutatum in strawberry planting material the following two years. A renovation programme was carried out, and in 2005 and 2006 C. acutatum was found in only one certified nursery. However, in 2007 latent infections of C. acutatum was detected in four certified strawberry plant nurseries. As been reported before from Norway, C. acutatum is present in almost all fruit and berry species grown in the country and has also been found on many ornamentals and in weeds, but it is a quarantine organism only in strawberry. It is particularly severe in cherry and apple. We have detected the perfect stage of the fungus in highbush blueberry, and when isolating the fungus we find a high frequency of isolates forming the perfect stage in culture. When doing genetic analysis (AFLP), the Norwegian isolates from strawberry separated in two groups. One set of isolates grouped together with strawberry isolates of C. acutatum from other countries, and the other set grouped with Norwegian isolates from several hosts, with a majority of isolates from sweet- and sour cherry. The latter group had more than 90% similarity between the polymorphic bands. There was also a third, very genetically diverse group of isolates that included most of the perithecia forming isolates. Further research will reveal if isolates from the different groups may vary in their aggressiveness to strawberry and if it will be possible to distinguish between them in simple molecular tests.
Forfattere
Arne Stensvand Maria Herrero Håvard Eikemo Andrew Dobson Belachew Asalf David M. Gadoury Robert C. Seem Catherine Heidenreich Mary Jean WelserSammendrag
Artikkelen omtalar resultat frå eit 4-årig prosjekt om mjøldogg i jordbær.