Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2009
Abstract
Growth and flowering of the annual-fruiting raspberry (Rubus idaeus L.) cultivar 'Polka' were studied under controlled environment conditions in order to facilitate out-of-season production. Vegetatively-propagated plants originating from adventitious root buds were used. Height growth and the rate of leaf formation increased with increasing temperature, up to a broad optimum in the mid-20 degrees C range. While elongation was consistently enhanced by long-day (LD) conditions, photoperiod had no effect on the rate of leaf formation. LD stimulation of growth thus resulted from increased internode length only. In agreement with earlier reports, it was found that, in contrast to biennial-fruiting cultivars, such annual-fruiting cultivars do not need low temperatures for flower initiation, nor do they appear to have a juvenile phase during which they are un-responsive to flower-inducing conditions. 'Polka' plants responded to inductive conditions as early as the 5-leaf stage, and flowered freely across the entire range of growth temperatures, even at 30 degrees C. Flowering was advanced and the number of flowers increased with increasing temperature, up to an optimum at 27 degrees C. Flowering was also consistently advanced and occurred at lower nodes under LD than under short-day (SD) conditions across the whole range of temperatures. Night interruption for 3 h in the middle of the night was also effective, demonstrating that this is a true photoperiodic response and not merely an effect of increased light integral in LD. It was also confirmed that a distinct vernalisation-type advancement of flowering took place when small, non-dormant plants were exposed to additional chilling at 6 degrees C for several weeks. At low temperatures, a large proportion of the lateral buds were dormant, so that, at 12 degrees C, the plants actually flowered only at their tips. Dissections also revealed that the dormant buds had initiated flowers; but, because of their dormant state, they needed several weeks of chilling before they could flower (biennial-fruiting behaviour). Both types of buds were initiated by the same environmental conditions. Practical applications of the findings are suggested.
Authors
Vibeke LindAbstract
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Authors
B. Kronvang H. Behrendt H. E. Andersen B. Arheimer A. Barr Stig A. Borgvang F. Bouraoui K. Granlund B. Grizzetti P. Groenendijk E. Schwaiger J. Hejzlar L. Hoffmann H. Johnsson Y. Panagopoulos A. Lo Porto H. Reisser O. Schoumans S. Anthony M. Silgram M. Venohr S. E. LarsenAbstract
No abstract has been registered
Abstract
Environmental control of flowering and runnering in three contrasting Fragaria chiloensis populations with geographic origins in Alaska, Oregon, and Chile have been studied under controlled environment conditions. All populations were principal short-day (SD) plants at intermediate temperatures (15 degrees C or 21 degrees C), while at low temperature (9 degrees C) the 'Alaska' and 'Chile' populations were essentially day neutral. However, the populations had contrasting temperature responses for flowering in SD at both constant and fluctuating day/night temperatures. At a day temperature of 18 degrees C, flowering increased with increasing night temperature from 9 degrees C to 21 degrees C in the 'Alaska' population, while the opposite trend was observed in the 'Chile' population. The sparsely flowering 'Oregon' population flowered only in SD within a narrow range of temperatures (15-18 degrees C). Photoperiod (10, 16, or 20 h) had no effect on flower development at 18 degrees C. All populations were runnering freely, but with different temperature and photoperiod modifications. It is concluded that the SD X temperature interaction in the flowering behaviour of the June-bearing cultivated strawberry, F. X ananassa, is inherited to a large extent from F. chiloensis, whereas the species does not appear to have contributed to the long-day (LD) flowering control in everbearing cultivars.
Authors
Øystein Johnsen Igor A. Yakovlev Carl Gunnar FossdalAbstract
Temperature during zygotic and somatic embryogenesis regulates an epigenetic memory in Picea abies. Conditions colder than normal advance the timing of bud burst and bud set, whilst temperatures above normal delay the onset of these processes. The long-lasting memory affects growth and hardiness in the field. We made a search of candidate genes and micro RNAs that could regulate the memory, using specialized library sequencing approaches. Two subtracted cDNA libraries, representing genes that are mainly expressed in plants from a cold (CE) or a warm (WE) embryogenesis, revealed considerable differences in the transcriptomes. Many contigs were unknown. We used qRT-PCR to demonstrate that five genes with no matching in the database were differentially expressed in close correlation with the memory-induced differences in bud set. Partial sequencing of two concatemerized small RNA libraries revealed 199 different small RNAs, with predominant length of 21-nt. We found 24 novel candidate miRNAs among them, and 4 described earlier. Most of the predicted miRNA targets were related to unknown and “no-hit” genes, 5 target different disease-related genes, and 4 contigs were homologous to described functional genes. Using qRT-PCR we confirmed that three selected genes regulated by miRNAs pab-miR100, 175 and 176, could to be involved in the memory regulation. Additionally, several novel miRNAs; pab-miR080, 105, 119, 122, 132, 144a,b and 157 were differentially expressed between epigenetically distinct plants. Our data illustrates that micro RNAs will guide us to candidate genes that are putative elements in the epigenetic machinery, regulating the long-lasting memory that affects adaptive traits in this species.
Authors
Knut Anders Hovstad Silje Borvik Mikael OhlsonAbstract
In modern agricultural landscapes, large herbivores are often restricted in their mobility or are found at low densities, and other animal vectors may therefore be important for seed dispersal. In our study, a range of plant species were able to disperse by attaching seeds to, and having their seeds retained in, the fox fur some distance. We suggest that the red fox may be an important vector for epizoochorous seed dispersal in the agricultural landscape.
Abstract
The report presents model simulations of irrigation water requirements over the period 1973-2008 for various crops in four regions of Norway. A detailed summary in English is given on pp. 47-49.
Authors
Belachew Asalf Tadesse Håvard Eikemo Andrew Dobson Anne-Marte Tronsmo Cecilie Hagen David M. Gadoury Robert C Seem Arne StensvandAbstract
Several non-chemical control agents are now registered and available for control of powdery mildews. However, there is little or no information about their efficacy against strawberry powdery mildew, caused by Podosphera aphanis. Trials were conducted to compare the performance of non-chemical control agents to chemical fungicides under laboratory, greenhouse and high plastic tunnel conditions. The treatments included: AQ10 (active ingredient is Ampelomyces quisqualis, a hyperparasite on powdery mildew), AQ10 + Silwet Gold (organosilicon adjuvant, enhances distribution and wetting), Vacciplant (active ingredient is laminarin, an extract from brown algae), JMS Stylet oil (mineral oil), Rape seed oil + detergent, Thiovit (wettable sulphur), Topas 100 EC (penconazole) + Candit (kresoximmethyl) and water as control. In the greenhouse, one quarter of the recommended dose was used either daily in one experiment or three times per week in another. In the field, half of recommended rates were applied twice weekly. Both in the greenhouse and tunnel experiments, the chemical control Topas + Candit and AQ10 + Silwet Gold significantly reduced disease severity. AQ10,Vacciplant and Thiovit were moderately effective when applied daily in the greenhouse trial, but not significantly different from the water control when applied three time per week in the greenhouse and twice a week in the tunnel experiment. In the plastic tunnel, the JMS stylet oil and Rape seed oil + detergent treatments caused severe phytotoxic reaction (necrosis). AQ10 used alone had the poorest performance in the tunnel. This indicated that the spreader either enhances the effect of AQ10 and/or the spreader itself had an effect. In laboratory experiments with powdery mildew grown on strawberry leaflets in Petri dishes, spore germination after treatments with water, Stylet oil, Candit and Thiovit were 74, 53, 8 and 7%, respectively. The effect of Thiovit found in the laboratory was not reflected in the greenhouse and plastic tunnel trials. We will further explore the protectant, curative and eradicative effects of the compounds included here.