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.
2011
Abstract
Recent research on how the structure and physiological development of red raspberry (Rubus idaeus L.) plants are controlled by genotype and the climatic environment is reviewed. Some older work, specially on plant structure relations, is also included. Physiological differences between annual- and biennial-fruiting plant types are highlighted. One major difference is the different requirements for flower formation. While biennial-fruiting cultivars have an absolute low temperature (≤ approx. 15°C) requirement for floral initiation, annual-fruiting cultivars readily initiate floral primordia at temperatures as high as constant 30°C. Also, while biennial-fruiting cultivars are facultative short-day plants with a critical photoperiod of 15 h at intermediate temperatures, flowering is promoted by long photoperiods in at least some annual-fruiting cultivars. However, the essential difference that determines whether the shoot life-cycle becomes annual or biennial is that, in biennial-fruiting genotypes, floral initiation is linked to the induction of bud dormancy, whereas in annual-fruiting cultivars, floral initiation is followed by direct flower development. Although this is genetically determined, it is a plastic trait that is subject to modification by the environment. Thus, at low temperatures and short photoperiods, the majority of initiated buds do enter dormancy also in annual-fruiting cultivars, with tip-flowering as a result. Practical applications are discussed, and it is concluded that our present physiological knowledge-base provides excellent opportunities for manipulation of raspberry crops for out-of-season production and high yields. It also provides a firm platform for further exploration of the underlying molecular genetics of plant structures and response mechanisms.
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Authors
Mekjell MelandAbstract
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Abstract
‘Summerred" apples (Malus domestica) Borkh are highly susceptible to biennial bearing if not properly thinned. This results in erratic yields and also affects fruit quality adversely. Between 2003 and 2005 ‘Summered"/‘M9" trees were treated with ethephon at concentrations of 250, 375 and 500 mL·L-1 when most king flowers opened (ca. 20% bloom) or at concentrations of 500, 625 and 750 mL·L-1 when the average fruitlet size was 10 mm in diameter. The experimental design was a completely randomised block design with 6 whole tree plots per replication. Trees were sprayed to the point of run-off with a hand applicator only when temperatures exceeded 15ºC. Within two weeks after the second application fruit set was reduced linearly with increasing concentrations of ethephon to less than 1 fruitlet per cluster at the highest concentrations used. Most thinning treatments reduced fruit set significantly compared to unthinned trees. Fruit numbers per tree decreased significantly with increasing ethephon concentrations, and the highest concentrations of ethephon applied during bloom or when the average fruitlet size was 10 mm in diameter resulted in over-thinning. Yield results confirmed the fruit set response where yield reductions were significant at highest concentrations of ethephon (2.1 kg·tree-1) compared to hand-thinned trees (7.3 kg·tree-1) in 2005. All thinning treatments resulted in higher percentage of fruits larger than 60 mm diameter average fruit size compared to unthinned control fruit. Thinning resulted in significantly higher soluble solid contents, and this was especially so for hand-thinned trees. Other fruit quality parameters like yellow/green background color did not show a clear response to thinning. Fruit firmness, however, decreased slightly in all ethephon treated trees whereas return bloom was improved on all thinned trees. It is recommended that ethephon be applied at a rate of 375 mL·L-1 when king flowers open or at a rate of 625 mL·L-1 when the average fruitlet size is 10 mm in diameter. These treatments thin ‘Summerred" apples to a target of about 5 fruits·cm-2 per trunk cross sectional area or 50-70 fruits·100 flower clusters-1 without impacting fruit quality, yield or return bloom the following year.
Authors
Clive Kaiser Philip B. Hamm Stacy Gieck Nicholas David Lynn Long Mekjell Meland J. Mark ChristensenAbstract
In vitro dose responses of several calcium and potassium salts were determined on some commercially significant plant pathogens including: Helminthosporium solani, Fusarium oxysporum f. sp. pisi race 2, Colletotricum coccodes, Phytophthora cactorum, Phytophthora cinnamomi, Phytophthora erythroseptica, Phytophthora infestans, Phytophthora megasperma, Pythium ultimum and Venturia inaequalis. Mycelial growth inhibition was both salt-specific and dose-related. Pythium ultimum was completely inhibited by ≥75 mg·L-1 calcium propionate, but needed ≥ 300 mg·L-1 of calcium acetate and ≥ 40 mL·L -1 of potassium silicate for complete inhibition. Phytophthora infestans was completely inhibited by ≥150 mg·L-1 calcium acetate, ≥150 mg·L-1 calcium propionate or ≥ 5 mL·L-1 potassium silicate. Phytophthora cactorum was completely inhibited by ≥ 300 mg·L-1 calcium propionate, but required ≥ 600 mg·L-1 calcium acetate and ≥10 mL·L-1 potassium silicate for complete inhibition. Phytophthora cinnamomi was completely inhibited by calcium propionate at ≥ 600 mg·L-1, or by ≥10 mL·L-1 potassium silicate. Only potassium silicate inhibited Phytophthora megasperma, Phytophthora erthroseptica, V. inequalis and H. solani at concentrations of ≥ 5mL·L-1, ≥ 20 mL·L-1, ≥ 40 mL·L-1 or ≥ 80mL·L-1 respectively. Potassium acetate did not completely inhibit any of the pathogens in this study when tested at concentrations ≤ 1200 mg·L-1.
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Authors
Merete Wiken Dees Arild Sletten Ricardo Holgado Eldrid Lein Molteberg Tor J. Johansen May Bente Brurberg Vinh Hong Le Ragnhild Nærstad Arne HermansenAbstract
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No abstract has been registered