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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.

2013

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Abstract

Seasonal time-courses of flower bud initiation and differentiation were monitored during two growing seasons (2011 and 2012) in 19 black currant cultivars of distant geographic origin, grown in the field at a South Norwegian locality (60°40’N, 10°52’E; 250 m asl). For comparison, the time-courses of shoot elongation growth in 15 of the same cultivars were also monitored during the 2012 growing season.The results revealed widely different seasonal timings of growth cessation and floral initiation in cultivars of different latitudinal origin. High latitude cultivars originating from crosses and selections of local, wild black currant populations from the Kola peninsula and Swedish Lapland were particularly early and had ceased growing and had initiated floral primordia by mid-June.This was approx. 5 – 6 weeks earlier than any of the other cultivars from lower latitudes. However, these also varied in their earliness of growth cessation and flower initiation in relation to their latitudinal origin. Many cultivars bred and selected in Southern Scandinavia, Scotland, and Poland did not cease growing and initiate floral primordia until late August, 9 weeks after the early, highlatitude cultivars. Overall, the 19 cultivars constituted a typical latitudinal cline in their photoperiodically controlled timing of growth and flowering responses. The high-latitude Russian cultivars ‘Imandra’ and ‘Murmanschanka’ represent valuable additions to the limited diversity of the available black currant gene-pool, and may be of particular use for breeding cultivars adapted to the sub-Arctic environment.

Abstract

Crop load adjustments in European plum trees (Prunus domestica L.) require thinning either by hand (mechanical) or chemical means to achieve marketable size, fruit quality and to overcome alternate bearing. Efficient tools for crop load management are highly desirable, since only a few chemical thinners are registered and hand thinning is labor intensive and costly. Gibberellic acid (GA3) was tested as a novel approach to regulate the crop load of the plum cultivar ‛Opal’ at Ullensvang, western Norway. The objective was to reduce flower bud induction in the “off-year” thus adjusting crop load the subsequent year. In 2008, an “off-year”, GA3 was applied to 9 year-old ‘Opal’ trees as a high volume spray to the point of run-off at 50 ppm or 100 ppm at either 5 weeks after full bloom or 10 weeks after full bloom, or on both dates and compared with untreated control trees. Trees were unthinned the first year but then thinned to commercial standard the following year. In the year of application, total yield was recorded and fruit quality evaluated. Return bloom, fruit set, yield and fruit quality were assessed the subsequent year. In general, there were no significant differences in crop load of all treated trees compared to untreated trees in the year of application (non-target crop) however, fruit weight increased slightly on those trees when GA3 was applied 5 weeks after full bloom compared to all other treatments and untreated trees. The following year (target crop) fruit set was significantly reduced for all GA3 treatments. The most effective application time was 5 weeks after full bloom. Before thinning, initial fruit set was greatest on untreated trees as well as on those trees treated with GA3 10 weeks after full bloom. Fruit weight and fruit colour were significantly better on trees with the least fruit set. GA3 applications had no effect on fruit firmness. It is concluded that GA3 is an effective tool for inhibiting flower bud induction in an “off-year” thus enabling crop load management the subsequent “on-year”.