Publikasjoner
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2016
Sammendrag
Satisfactory seed yield of red clover (Trifolium pratense L.) cultivars is crucial for the availability of seeds on the market. Many breeders and researchers have used seed yield components to measure, compare, and explain differences in seed yield between diploid and tetraploid red clover cultivars and populations; however, the relative importance of each component varies between studies. In 2011 and 2012, single-plant trials with several tetraploid and one diploid red clover cultivar were established at the Norwegian plant breeding station at Bjørke. The goal was to study the impact of different seed-yield components on the seed yield of tetraploid plants. Seed weight per flower head was the seed-yield component that correlated best with the seed yield plant−1 (r = 0.91 and r = 0.68 in 2011 and 2012, respectively). Path coefficient analysis has also shown that the seed weight per flower head had the highest direct impact on seed yield plant−1 (direct path coefficients were 0.867 and 0.783 in 2011 and 2012, respectively). In comparison, the direct path coefficients for calculated number of flower heads, which was previously highlighted as the most important seed-yield component, were lower and more variable (0.739 and 0.392 in 2011 and 2012, respectively). Since previously seed yield per flower head was also identified as the most important seed-yield component in dense plant canopy, this component might have the potential to select for improved seed yield of new cultivars based on single plants. However, further studies are required to confirm this conclusion.
Forfattere
Helga Amdahl Trygve S. Aamlid Åshild Ergon Mallikarjuna Rao Kovi Petter Marum Muath K Alsheikh Odd Arne RognliSammendrag
While tetraploid plants of red clover are taller, have thicker stems, and have broader leaves that altogether result in a higher forage yield compared to diploids, they generally have substantially lower seed yields than diploid plants. Tetraploid red clover can be induced chemically by colchicine or nitrous oxide (N2O) and sexually by union of unreduced gametes. The average seed yield of tetraploid red clover in Norway is 60% of the diploid yield, while in Sweden it is 75%. One objective of this paper was to examine whether there is a difference in seed yield among chromosome doubled tetraploids and crossed tetraploids. A second objective was to investigate differences in seed yield and seed yield components in Norwegian and Swedish tetraploid populations. The third objective was to study which yield component most correlates with the seed yield per hectare. Seed production experiments were established at Landvik and Bjørke in Norway and Svalöv and Lännäs in Sweden. Populations made by crossings of tetraploids gave significantly greater yield (p < 0.001) compared to populations that were made by chromosome doubling. On average, Norwegian and Swedish varieties had equal yields in both experimental years. Norwegian and Swedish varieties differed mostly in earliness traits. Swedish populations began flowering on average 4 d earlier than Norwegian populations. Genotypic correlations showed that seed yield per flower head was the component with the highest correlation (r = 0.956 and r = 0.977) with yield per hectare in both experimental fields. Results from the second experimental year indicate a trend towards improved seed yield after several cycles of recurrent selection for higher seed yield per flower head.
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Forfattere
Bjørn Egil FløSammendrag
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Forfattere
Louise C. Ross Gunnar Austrheim Leif Jarle Asheim Gunnar Bjarnason Jon Feilberg Anna Maria Fosaa Alison J. Hester Øystein Holand Ingibjörg S Jónsdóttir Lis E. Mortensen Atle Mysterud Erla Olsen Anders Skonhoft James David Mervyn Speed Geir Steinheim Des B.A. Thompson Anna G. ThorhallsdottirSammendrag
Sheep grazing is an important part of agriculture in the North Atlantic region, defined here as the Faroe Islands, Greenland, Iceland, Norway and Scotland. This process has played a key role in shaping the landscape and biodiversity of the region, sometimes with major environmental consequences, and has also been instrumental in the development of its rural economy and culture. In this review, we present results of the first interdisciplinary study taking a long-term perspective on sheep management, resource economy and the ecological impacts of sheep grazing, showing that sustainability boundaries are most likely to be exceeded in fragile environments where financial support is linked to the number of sheep produced. The sustainability of sheep grazing can be enhanced by a management regime that promotes grazing densities appropriate to the site and supported by area-based subsidy systems, thus minimizing environmental degradation, encouraging biodiversity and preserving the integrity of ecosystem processes.
Forfattere
Radoslaw Juszczak Bogdan Chojnicki Marek Urbaniak Jacek Leśny Hanna Marika Silvennoinen Mariusz Lamentowicz Anna Maria Basinska Maciej Gabka Marcin Stróz ̇ecki Mateusz Samson Dominika Łuców Damian Józefczyk Mathias Hoffmann Janusz OlejnikSammendrag
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Forfattere
Nicholas Clarke Hugh Cross Toril Drabløs Eldhuset Kjersti Holt Hanssen Ari Hietala O. Janne Kjønaas Holger Lange Jørn-Frode Nordbakken Tonje Økland Ingvald Røsberg Silje SkårSammendrag
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