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
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2008
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Authors
Aslaug Helgadottir Petter Marum Sigridur Dalmannsdottir Kristin Daugstad Thordis Anna Kristjansdottir Tor LunnanAbstract
Background and aims: White clover (Trifolium repens) is an important component of sustainable livestock systems around the world. Its exploitation for agriculture in the northern, marginal areas, is, however, currently limited by the lack of cultivars that combine persistence and high production potential. The aims are to investigate whether it is feasible to create breeding material of white clover for these areas by combining winter hardiness of northerly populations with good yielding ability of more southerly cultivars. Methods: A total of 166 crosses of 14 different parental combinations between winter-hardy, low-yielding populations of northern origin and high-yielding commercial cultivars of more southerly origin were tested under field conditions in Iceland and Norway and the parental combinations were compared in Norway. Spaced plants were transplanted into a smooth meadow grass (Poa pratensis) sward. Dry matter yield was estimated for 2 years after planting in Norway and morphological characters associated with yielding capacity were measured at both sites. Key results: The results showed that southerly cultivars had larger leaves and higher yielding potential than northern types but suffered more winter damage. Significant variation was found between full-sib families within the different parental combinations for all morphological characteristics measured in all three trials. However, it was difficult to detect any consistens morphological patterns between progeny groups across trial sites. No significant correlations were found between leaflet area and survival. Conclusions: The present study has confirmed that it should be possible to simultaneously select for good winter survival and larger leaves and, hence, higher yielding ability under marginal conditions.
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Due to a late harvesting season compared to that found in other European countries, the sweet cherry industry in Norway is now expanding, aiming for export markets. Cultivars producing high quality fruit that ripen late (late July and throughout August) and that are suitable to grow in high density production systems are sought. In addition, early ripening cultivars are sought for local marketing in early and middle July. Testing cultivars and advanced selections has been carried out at Ullensvang Research Centre since 1959. During the last decade, 130 cultivars and advanced selections have been included in the testing program. Important parameters like fruit size, fruit firmness, low fruit cracking, high and precocious yield, fresh appearance and good flavour have been evaluated. Based on the results from this testing program, the following cultivars are currently recommended: a) for early season: `Burlat", `Moreau" and `Merchant", b) for mid-season: `Giorgia", `Chelan", `Samba", `Techlovan" and `Van", c) for late season: `Lapins", `Kordia", `Regina" and `Sweetheart".
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Some high density sweet cherry orchards in Norway suffer from decay of trees resulting in death or reduced vigour of trees. A survey monitoring healthy and infected trees from several orchards found differences between cultivars and rootstocks in sensitivity of tree decay. In order to investigate this cherry tree decay further, new field trials were established in 2002 with trees of the cultivar Van grafted on the two rootstocks Prunus avium seedling and Colt and trained as central leader trees. Two parallel trials were planted; one in the soil of an old cherry orchard and the other in the soil from agricultural land where no fruit production had been conducted in advance. During the first years significant larger annual vegetative growth measured as trunk girth, annual shoot growth and leaf areas were registered from the trees growing in the virgin soil. In the replanted cherry soil, trees grafted on the rootstock Colt grew more vigorously than the seedling rootstock based on leaf areas and shoot growth measurements. The rootstock Colt may be the answer for avoiding cherry replant diseases.
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