Anita Sønsteby
Research Professor
Authors
Samia Samad Rodmar Isak Rivero Pruthvi Balachandra Kalyandurg Ramesh Raju Vetukuri Ola M. Heide Anita Sønsteby Sammar KhalilAbstract
Floral transition in the cultivated everbearing strawberry is a hot topic because these genotypes flower perpetually and are difficult to maintain in a non-flowering state. However, it has rarely been studied using morphogenetic and molecular analyses simultaneously. We therefore examined the morphogenetic effects and the activation of genes involved in floral induction and initiation in seedlings of an everbearing F1-hybrid. Seedlings were grown at 12, 19, and 26 °C under 10 h SD and 20 h LD conditions. We observed a strong environmental influence on meristem development and a FLOWERING LOCUS T1 (FaFT1)–SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (FaSOC1) pathway similar to that in the everbearing woodland strawberry. The everbearing cultivar showed typical features of a quantitative LD plant, flowering earlier under LD than SD conditions at all temperatures. We also found that floral induction is facilitated by FaFT1 upregulation under LD conditions, while FaSOC1 upregulation in the apex leads to photoperiod-independent floral initiation. Moreover, we confirmed the strawberry meristem identity gene FaFUL can also be used as an early indicator of floral initiation in EB cultivars. This study also highlights the advantages of seed-propagated F1-hybrids in genetic studies, namely that they are genetically identical and not biased by a previous flowering history.
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Environmental control of flowering in everbearing strawberry is well known, while the optimal commercial raising conditions for high and continuous yield remains unsettled. We exposed freshly rooted plants of cultivars Altess, Favori and Murano to 9 °C, 15 °C, 21 °C and 27 °C, respectively, at two photoperiods for 4 weeks, and assessed flowering and yield performance. Long days at 15–21 °C enhanced flowering, while short days (SD), particularly at 27 °C, decreased flowering. Runner formation was enhanced by SD, being inversely related to flowering. Yields the next season were highest in plants exposed to 15–21 °C, whereas the seasonal harvest distribution varied. In concurrence with earlier reports, the size of the first fruit flush determined the magnitude of the second flush and the length of the off period when little fruit was produced. The large first fruiting flushes of plants exposed to 21 and 27 °C gave particularly long off periods and small second flushes. Moderate first flushes of plants from intermediate temperatures also resulted in a more evenly distributed harvest and the largest yields. Developing flowers and fruits are strong sinks for photosynthates; therefore, the size of the first fruit flush must be compromised to optimize fruit yield and seasonal crop distribution.
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The morphogenetic changes of the bud meristem during floral initiation in gooseberry were examined by scanning electron microscopy. Six floral stages, similar to those reported for black currants, were identified. We also studied the environmental control of shoot growth and floral initiation of cvs. Mucurines, Pax and Xenia in two experiments in daylight phytotron compartments at 12, 18 and 24°C. Under natural daylength conditions at Ås, Norway (69°40’N), shoot growth started to decline by mid-August and ceased in early September. Cessation of growth was associated with floral initiation at 18 and 12°C, while at 24°C, only ‘Mucurines’ initiated floral primordia. Floral Stage 2 was reached by 3 September in ‘Mucurines’ and ‘Xenia’ at 18 and 12°C and nearly 2 weeks later in ‘Pax’. In a second experiment with controlled photoperiods, all cultivars ceased growing and initiated flowering in 10-h SD within 2–3 weeks, while in 20-h LD, growth continued for 8 weeks without floral initiation. Under 10-h SD conditions, all cultivars initiated flowers also at 24°C. Flowering performance in the following spring verified these results. We conclude that gooseberry is an obligatory SD plant with a critical photoperiod of 15–16 h.
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Background There is limited information on the effect of environment on vegetative growth in everbearing (EB) strawberry (Fragaria x ananassa Duch.) and its comparison with the situation in seasonal flowering types. Methods We investigated the effects of photoperiod (daylengths of 10 and 20 h) and temperature (12, 19 and 26 ℃) on leaf growth, dry matter production and partitioning, concentrations of soluble sugars, starch, and chlorophyll in the F1 hybrid ‘Delizzimo’ grown in a single experiment in daylight phytotron compartments in Norway. Results Plants grown in the long photoperiod (LD) and higher temperatures had greater leaf growth and higher dry matter production than those under short day (SD) and low temperature conditions. Growth decreased over the 39 days of the experiment. The changes in growth in the different environments were associated with changes in relative growth rate (RGR) and these were driven by changes in net assimilation rate (NAR) and leaf area ratio (LAR). The plants directed more dry matter to the leaves and crowns under LD and high temperature conditions and less dry matter to the roots, thus increasing the plant’s shoot to root ratio. Long days decreased the concentrations of sugars and starch in most of the tissues, while the effect of temperature was more complex. Higher temperatures increased the concentrations of sugars in the leaves in LD, while starch accumulated in the roots under SD and low temperature conditions. Sucrose accumulated temporarily in the crowns at the time of flower bud formation in LD and higher temperatures. Conclusions The results of the experiment demonstrate that the effects of photoperiod and temperature on the vegetative growth of everbearing strawberry are similar to those reported for seasonal-flowering strawberry. Increases in temperature and photoperiod and the resulting enhancement of the RGR was associated with accumulation of soluble sugars (sucrose, glucose and fructose) in the above-ground parts of the plant, whereas low temperature and SD resulted in accumulation of starch in the roots.
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Environmental conditions during plant raising determine the yield potential of everbearing strawberries. We studied the effect of three rooting dates in the cultivars ‘Favori’ and ‘Murano’ in a greenhouse with 18 ℃ and 20-h long day and under outdoor conditions in Norway. The highest yield of 1.350 g/plant was obtained in ‘Favori’ plants rooted on 1 August and raised outdoors, being at level with ‘Favori’ plants produced in The Netherlands. High yields were mainly related to fruit size and less to fruit number, and determined by a complex three-factor interaction of rooting date, raising environment, and cultivar. The seasonal pattern of fruit flushes and off periods varied significantly between cultivars and treatments. The large first flush of high yielding ‘Favori’ plants was associated with a long off period, while the small first flush in ‘Murano’ resulted in a more even crop distribution. Earliness of ripening and berry harvest was superior in ‘Favori’, which had a larger share of its crop during the first half-season. We conclude that it is possible by choosing the right rooting date and raising environment to produce plants with the same high quality and yield potential under the cool Nordic conditions as those currently produced in Central Europe.
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Horticultural production systems are under pressure to find environmentally friendly growing media. Peat is currently the most popular substrate for fresh potted herbs production; however, this raw material is not sustainable due to the large amount of greenhouse gases released during its harvesting. Therefore, the goal of the study was to test the performance of various commercial wood fiber products and compare them with peat and coir in an ebb-and-flow production system with basil (Ocimum basilicum L. 'Marian'). Basil plants were grown in three different pot sizes (6, 9 and 12 cm in diameter) and under various fertigation regimes (EC 1, 2 and 3). Height and biomass of the plants were recorded when the best performing plants reached the commercial stage. The tallest plants and greatest biomass were produced in peat and coir, however, the results confirm that wood fiber can be a promising substrate alternative. Further research is needed to study, among others topics, how to modify some properties of wood fibers to fulfil their potential as a replacement for non-sustainable growing media in production of herbs in pots.
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No abstract has been registered
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Background Dormancy regulation in strawberry is a dynamic process that is causally interrelated with regulation of flowering. Interference between the two processes is therefore possible. Methods We studied dormancy control and its relation to flowering and runner formation in ‘Sonata’ strawberry under daylight phytotron conditions. Growth and flowering were observed in plants pretreated for 5 or 10 weeks at 10-h SD and 18-h LD at 6 and 18 ℃ and subsequently forced in a greenhouse in LD at 20 ℃ with and without previous chilling for 6 weeks at 2 ℃ in darkness. Results SD induced constrained leaf and inflorescence growth at both 6 and 18 ℃, while the typical strawberry semi-dormant condition was attained only by exposure to SD at 18 ℃ for 10 weeks, which also completely blocked runner formation. The constrained leaf and inflorescence growth observed in plants grown in SD at 18 ℃ were partially reversed by 6 weeks of chilling and gradually overcome in successively emerging leaves. While plants grown in LD at 18 ℃ for 10 weeks remained vegetative under subsequent forcing, they unexpectedly initiated flowers when subjected to chilling in darkness for 6 weeks before the forcing. Conclusions SD exposure at 18 ℃ constrained leaf and inflorescence growth in ‘Sonata’ strawberry, and when applied for 10 weeks, it induced the persistent semi-dormant state that is typical for strawberry. Transient growth constraints were also induced at 6 ℃ in both SD and LD, while the semi-dormant state was only attained by SD at the higher temperature. Flowering in complete darkness, which is known in both SD and LD plants, did also take place in ‘Sonata’ strawberry in response to chilling in the dark at 2 ℃ for 6 weeks. While the potential impact of the phenomenon seems limited for regulation of flowering in strawberry, we conclude that chilling in the dark at near-freezing temperature may substantially enhance flowering in marginally induced strawberry plants.
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It is not known to what degree growth and fruit yield are source-limited in everbearing strawberry plants. The growth and yield performance effect of bi-weekly removal of all runners and/or one or two leaves during the cropping season of tunnel-grown ‘Favori’ everbearing strawberry plants was determined. Plants were grown on a table-top system in an open plastic tunnel under natural light conditions in Norway from May to October. Removal of runners and leaves was bi-weekly from 5 June until 25 September. Fruits were harvested from 5 July to 7 October. Bi-weekly runner removal increased total and marketable yield and number and size of fruits, while increasing leaf thinning had the opposite effects. However, none of the treatments affected the fruit number and yield of the first fruiting flush. The treatments did not affect realization of the yield potential of the plants at planting, whereas the continued floral initiation and fruit growth were enhanced by runner removal. Increasing leaf thinning had the opposite effects. Both floral initiation and fruit growth in heavily flowering and fruiting everbearing strawberry are source-limited owing to the high fruit/leaf ratio of such plants.
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The growing interest in using everbearing (EB) strawberry cultivars to extend the cultivation period has faced some challenges. These include poor runner production due to its perpetual flowering nature; irregular flowering behavior and extended periods of high temperature have caused floral inhibition and reduced yield. As flowering is an interplay between temperature and photoperiod, it is important to investigate the effects of this interaction on the cultivation. Therefore, this study used meristem dissection as a tool to study the effect of temperature and photoperiod on meristem development. Tray plants of two EB strawberry cultivars ‘Florentina’ and ‘Favori’ were grown at 20 °C, 25 °C, and 30 °C under short day (SD) conditions, and subsequently at 20 °C under long day (LD) conditions. The meristem development was analysed every 6 weeks for a 15-week period in SD and for 14 weeks in LD conditions using meristem dissection. The plants showed similar flowering patterns to previously studied everbearing cultivars, which was qualitative LD plants at high temperatures and quantitative LD plants at lower temperatures. Our results show that meristem dissection can be used to determine the temperature and photoperiodic effect on meristem development, and for the occurrence of cropping peaks, and can therefore be used to decide the environmental input and to evaluate yield potential.
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There is little knowledge about photosynthesis in everbearing strawberry cultivars. We therefore grew three everbearing strawberry cultivars in daylight phytotron compartments at temperatures of 9, 15, 21 and 27°C and photoperiods of 10 h (SD) and 20 h (LD). After three weeks, the rates of dark respiration and photosynthesis and their acclimation were measured in 'Favouri'. Photosynthesis of plants grown in the various conditions was measured as CO2-uptake with an infrared gas analyzer at increasing irradiances (50-1000 µmol quanta m‑2 s‑1) and temperatures ranging from 9 to 27°C. In the dark, CO2-production (dark respiration) increased with increasing measuring temperature and was always largest in plants grown at low temperature (9°C) with no significant effect of photoperiod. Photosynthetic CO2-uptake was lowest at almost all irradiances in plants grown at 9°C, and with no clear effect of growth temperatures in the 15-27°C range. At saturating irradiances (500-1000 µmol), CO2-uptake increased with increasing measuring temperatures, reaching a plateau at about 21°C for plants grown at 15-27°C in SD and at 21-27°C in LD. For plants grown at 15°C in LD, the maximum CO2-uptake rate was obtained at 27°C. Light response curves showed that CO2-uptake increased with increasing irradiance and measuring temperatures and that the irradiance effect was markedly enhanced by increasing growth temperature. Maximum uptake rates were lowest for plants grown at 9°C at both photoperiods and highest for plants grown at 15°C in SD. Comparison of plants of 'Altess', 'Favouri' and 'Murano' at 500 µmol irradiance and 21°C revealed no significant differences in photosynthetic efficiency between the cultivars. Generally, the everbearing strawberry cultivars showed considerable photosynthetic plasticity to temperature within the 9-27°C range, although with an overall optimum at 15-21°C.
Authors
Anita SønstebyAbstract
No abstract has been registered
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The environmental control of dormancy and its relation to flowering and runner formation is poorly understood in everbearing (EB) strawberry cultivars. We studied the topic by growing plants of the seed-propagated F1-hybrid ‘Delizzimo’ and the runner-propagated ‘Favori’ cultivar in daylight phytotron compartments under short day (SD) and long day (LD) conditions at temperatures of 6, 16 or 26 °C for 5 and 10 weeks. This was followed by forcing at 20 °C and 20-h photoperiod for 10 weeks with and without preceding chilling at 2 °C for 6 weeks. The results showed that dormancy in EB strawberry is regulated by a complex interaction of temperature, photoperiod and chilling in much the same way as known for seasonal flowering (SF) cultivars. Surprisingly, the EB cultivars exhibited the same SD dormancy induction response as SF cultivars, despite their opposite photoperiodic flowering requirements. However, at 26 °C the EB cultivars developed partial dormancy also under LD conditions. As known for SF cultivars, none of the EB cultivars became dormant at 6 °C regardless of daylength conditions, whereas they were increasingly sensitive to SD dormancy induction at intermediate and high temperatures. Similar to SF cultivars, the EB cultivars needed exposure to SD and relatively high temperatures for at least 10 weeks for attainment of the semi-dormant state that is typical for strawberry in general. As reported for SF cultivars, there was a close interrelation between the control of flowering, runner formation and dormancy also in the EB cultivars. ‘Favori’ had an obligatory LD requirement for flowering at 26 °C and was almost day neutral at 16 °C, while ‘Delizzimo’ behaved as a quantitative LD plant at both temperatures, and both cultivars were completely day neutral at 6 °C. Except for the stricter LD control of flowering in ‘Favori’, the overall environmental responses were quite similar in the two genetically distant cultivars. Chilling for six weeks at 2 °C was adequate for complete reversal of the constrained elongation of leaf petioles and flower trusses in dormant plants, but had little or no effect on the degree of flowering and runner formation.
Authors
Anita SønstebyAbstract
No abstract has been registered
Authors
Tomasz Leszek Woznicki Krzysztof Kusnierek Unni Myrheim Roos Sofie Andersen Katrin Zimmer Anita SønstebyAbstract
The use of peat as a growing media in horticulture is supposed to be reduced due to negative effects of its production on the environment. Interest in development of alternative growing media is therefore increasing and is enhanced by both political pressure and industry demands. Therefore, the influence of 33 growing media on the performance and productivity of two strawberry cultivars were examined in a polytunnel under Nordic conditions (60.7 N). Alternative substrates including fibers of spruce, birch and flax and coffee grounds were tested standalone or in mixes. Peat and coir were included as controls. Additionally, impregnation of the wood fibers with organic and inorganic substances was examined. All investigated growing media received identical fertigation strategies (EC 1.5). The highest average biomass production was observed for plants grown in bare peat; however, the best yield performance was noted for peat mixed with perlite and for coarse spruce fiber. Strawberries grown in these two best performing substrates showed comparable overall productivity, with 272 and 268 g of berries per plant, respectively. Both peat/perlite mix and the coarse spruce fiber had also a similar weight of berries larger than 25 mm, with 210 and 198 g plant-1, respectively. Moreover, improvement of the substrate structure by adding perlite or wood chips may have had a pronounced effect on fruiting performance. When compared to peat with added perlite (which gave the highest berry yield in the experiment; 272 g plant-1), strawberries grown in pure peat produced only 187 g plant-1. Furthermore, impregnation of spruce fiber with humic acid enhanced fruiting performance by increasing the total yield and number of large berries (≥25 mm). Future prospects for this study include establishment of an optimal structure of spruce fiber substrate suitable for strawberry production and development of the fertigation strategy optimized for the new growing media.
Authors
Sara Durán-Soria Delphine M. Pott Frank Will Jennifer Mesa-Marín Mariusz Lewandowski Karolina Celejewska Agnieszka Masny Edward Zurawicz Nikki Jennings Anita Sønsteby Erika Krüger Sonia OsorioAbstract
Promoting the consumption of fruits is a key objective of nutrition policy campaigns due to their associated health benefits. Raspberries are well appreciated for their remarkable flavor and nutritional value attributable to their antioxidant properties. Consequently, one of the objectives of present-day raspberry breeding programs is to improve the fruit’s sensory and nutritive characteristics. However, developing new genotypes with enhanced quality traits is a complex task due to the intricate impacts genetic and environmental factors have on these attributes, and the difficulty to phenotype them. We used a multi-platform metabolomic approach to compare flavor- and nutritional-related metabolite profiles of four raspberry cultivars (‘Glen Ample’, ‘Schönemann’, ‘Tulameen’ and ‘Veten’) grown in different European climates. Although the cultivars appear to be better adapted to high latitudes, for their content in soluble solids and acidity, multivariate statistical analyses allowed us to underscore important genotypic differences based on the profiles of important metabolites. ‘Schönemann’ and ‘Veten’ were characterized by high levels of anthocyanins and ellagitannins, respectively, ‘Tulameen’ by its acidity, and ‘Glen Ample’ for its content of sucrose and β-ionone, two main flavor contributors. Our results confirmed the value of metabolomic-driven approaches, which may foster the development of cultivars with enhanced health properties and flavor.
Authors
Erika Krüger B. Brauksiepe P. Chartier M.-N. Demene B. Denoye K. Eimert I. Sowik A. Masny G. Savini Anita SønstebyAbstract
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Anita SønstebyAbstract
No abstract has been registered
Authors
Erika Krüger Frank Will Keshav Kumar Karolina Celejewska Philippe Chartier Agnieszka Masny Daniela Mott Aurelie Petit Gianluca Savini Anita SønstebyAbstract
The effect of cultivar and environmental variations and their interaction on anthocyanin components of strawberry were assessed for six cultivars grown in five locations from North to South of Europe in two different years. To evaluate the impact of latitude- and altitude-related factors, daily mean (Tmean), maximum (Tmax) and minimum (Tmin) temperature and global radiation accumulated for 3, 5, 10 and 15 days before fruit sampling, was analyzed. In general, fruits grown in the south were more enriched in total anthocyanin and pelargonidin-3-glucoside (pel-3-glc), the most abundant anthocyanin in strawberry. Principal component analysis (PCA) provided a separation of the growing locations within a cultivar due to latitudinal climatic differences, temporary weather changes before fruit collection and cultivation technique. PCA also depicted different patterns for anthocyanin distribution indicating a cultivar specific reaction on the environmental factors. The linear regression analysis showed that pel-3-glc was relatively less affected by these factors, while the minor anthocyanins cyanidin-3-glucoside, cyanidin-3-(6-O-malonyl)-glucoside, pelargonidin-3-rutinoside and pelargonidin-3-(6-O-malonoyl)-glucoside were sensitive to Tmax. The global radiation strongly increased cya-3-mal-glc in ‘Frida’ and pel-3-rut in ‘Frida’ and ‘Florence’. ‘Candonga’ accumulated less pel-3-glc and total anthocyanin with increased global radiation. The anthocyanin profiles of ‘Gariguette’ and ‘Clery’ were unaffected by environmental conditions.
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Hydroponic production of strawberry (Fragaria × ananassa Duch.) in protected cultivation systems using substrates (growing media) is gaining popularity worldwide. Therefore, it is necessary to develop more sustainable growing media alternatives. This study focused on growth performance of strawberry plants grown in wood fibre from Norway spruce (Picea abies (L.) H. Karst.), in comparison to two industry standards (peat and coco fibres). Plug (tray) plants of the June-bearing strawberry cultivar 'Malling Centenary' and bare root (WBH) plants of cultivar 'Sonata' were transplanted into three different growing media: peat (80%) and perlite (20%) mixture, coconut coir (100%) and Norway spruce wood fibre (100%). The plants received four fertigation strategies (various potassium and nitrogen concentrations) from flowering onwards. Throughout the production season ripe berries were harvested and frozen for later analyses of chemical composition. Plant architecture was also recorded after termination of the experiment. The results revealed that the most significant differences among the majority of the fruit and plant parameters were due to cultivar traits. Strawberries grown in wood fibre produced slightly smaller berries with elevated °Brix and dry matter compared to berries from plants grown in peat and coir. This was most likely caused by the common fertigation strategy applied to all substrates. Nevertheless, among the tested fertigation strategies, application of solutions with elevated potassium resulted in the highest sugar accumulation in berries grown in wood fibre substrate. In general, the experiment revealed relatively negligible differences between the growing media, and we therefore conclude that wood fibre from Norway spruce may be a viable alternative as a growing media in hydroponic strawberry production when the fertigation strategy is precisely adjusted.
Authors
Anita SønstebyAbstract
No abstract has been registered
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BACKGROUND: Bud dormancy is a quantitative condition that is gradually acquired and lost. Better and more convenient methods for assessment of the time of dormancy entrance of woody plants are highly needed. OBJECTIVE: To demonstrate a simple and convenient method for determination of dormancy in woody plants. METHODS: We employed a seasonal series of soft tipping of vigorously growing annual shoots and used the loss of ability of subtending lateral buds to break and grow as a measure of entrance into dormancy. RESULTS: There was a gradual decline in the ability of the buds to burst and grow during the month of July and early August, culminating with a complete loss of this ability. This coincided with the known time of growth cessation and dormancy induction in shoots of intact plants and occurred in the berry shrubs raspberry and black currant and the forest tree silver birch. CONCLUSIONS: The decline and loss of ability of the buds to grow during late summer is a direct expression of the entrance of buds into the state of endodormancy, rendering the tipping method a simple and convenient method for precise determination of the time of entrance into dormancy in woody plants.
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BACKGROUND:The predicted and ongoing climate warming can have far-reaching effects on plant growth and life cycle. Therefore, there is need for simple and convenient methods for analysis and monitoring of consequences of the ongoing warming. OBJECTIVE:To demonstrate the usefulness of so-called climate-photothermographs for studying the consequences of the ongoing warming for production of berry crops. METHODS:Local photothermal climates can be expressed by so-called climate-photothermographs, which show the relationship between temperature and daylength for each month of the year in a rectangular coordinate diagram. When superimposing critical response curves for plant development processes on top of such a diagram, the limitations of the given climate for fulfilment of the processes can be readily assessed. RESULTS:Consequences of 2°C warming for critical development processes such as transition to flowering and breaking of winter dormancy in the berry crops raspberry, black currant and strawberry were clearly exposed by the technique. The locations Geisenheim, Germany and Ås, Norway were used as examples. Inadequate winter chill was identified as the most limiting factor for these crops. CONCLUSIONS:We conclude that the technique is an efficient and convenient tool for monitoring the consequences of climate warming for berry crops.
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Four raspberry cultivars were grown at two different latitudes namely in Geisenheim (DE, 49°60’N; 7°57’E) and in Kapp (NO, 60°42’N; 10°52’E) to investigate the impact of these growing sites on primary and secondary fruit chemical ingredients in the 2017 season. Fruits were harvested at two picking dates each with three field replications. Contents of °Brix, glucose, fructose, sucrose, organic acids, ascorbic acid, polyols, total polyphenols, and anthocyanins were analyzed in the fruits. The geographic growing sites, which in this case is more than10 latitudes between HGU in Germany and NIBIO in Norway, has partly no, partly significant effects on the primary and secondary ingredients of the investigated raspberry cultivars. In respect to the created data set, temperatures shortly before or at the picking dates were not considered. It may be expected that temperatures at harvest have an effect on the fruit ingredients and therefore on a further classification of the samples.
Authors
Sara Duran-Soria Delphine M. Pott William Allwood Erika Krüger Anita Sønsteby Agnieszka Masny Björn Usadel Dorota Jarret Sonia OsorioAbstract
No abstract has been registered
Authors
Anita SønstebyAbstract
No abstract has been registered
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Anita SønstebyAbstract
No abstract has been registered
Authors
Anita SønstebyAbstract
No abstract has been registered
Authors
Anita SønstebyAbstract
No abstract has been registered
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Growth cessation and floral initiation in black currant and red raspberry are jointly controlled by the interaction of temperature and short-day (SD) conditions, and the processes coincide in time in both natural and controlled environments. The critical photoperiods for the two successional responses were found to be approximately 15 and 16 h, respectively, for a range of Western-European black currant cultivars. Both cessation of growth and floral initiation are promoted and enhanced by increasing temperature in the 9 to 24°C range. In contrast, biennial-fruiting red raspberry has a maximum temperature limit for growth cessation and floral initiation. At temperatures above 16°C, most cultivars grow and remain vegetative regardless of day length conditions, at 12 to 16°C they cease growing and initiate flower primordia in photoperiods <15 h, while at temperatures ≤12°C they cease growing and initiate floral primordia regardless of day length. In the annual-fruiting (primocane) types of red raspberry on the other hand, floral initiation is not constrained by high temperature, but readily takes place at temperatures up to 30°C. In addition, floral initiation is also enhanced by long day (LD) conditions in most of these cultivars. Another fundamental physiological difference is that while floral primordia of the biennial types become dormant after initiation, they proceed directly to anthesis in the annual-fruiting types. Chilling at -5°C, and in the -5 to +5°C temperature range were found to be optimal for breaking of bud dormancy and promotion of flowering in black currant and red raspberry, respectively. In black currant, 14 weeks of chilling were optimal, while for raspberry, 20 or more weeks were required for full dormancy release and promotion of flowering along the entire length of the raspberry cane. The consequences of climate warming for the production of these species in different climatic regions are discussed.
Authors
Anita SønstebyAbstract
No abstract has been registered
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Anita SønstebyAbstract
No abstract has been registered
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Anita SønstebyAbstract
No abstract has been registered
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Authors
J. William Allwood Tomasz Leszek Woznicki Yun Xu Alexandre Foito Kjersti Aaby Julie Sungurtas Sabine Freitag Royston Goodacre Derek Stewart Siv Fagertun Remberg Ola M Heide Anita SønstebyAbstract
Introduction Blackcurrant (Ribes nigrum L.) is an excellent example of a “super fruit” with potential health benefits. Both genotype and cultivation environment are known to affect the chemical composition of blackcurrant, especially ascorbic acid and various phenolic compounds. Environmental conditions, like temperature, solar radiation and precipitation can also have significant impact on fruit chemical composition. The relevance of the study is further accentuated by the predicted and ongoing changes in global climate. Objectives The aim of the present study was to provide new knowledge and a deeper understanding of the effects of post flowering environmental conditions, namely temperature and day length, on fruit quality and chemical composition of blackcurrant using an untargeted high performance liquid chromatography–photo diode array–mass spectrometry (HPLC– PDA–MS) metabolomics approach. Methods A phytotron experiment with cultivation of single-stemmed potted plants of blackcurrant cv. Narve Viking was conducted using constant temperatures of 12, 18 or 24 °C and three different photoperiods (short day, short day with night interruption, and natural summer daylight conditions). Plants were also grown under ambient outdoor conditions. Ripe berries were analysed using an untargeted HPLC–PDA–MS metabolomics approach to detect the presence and concentration of molecules as affected by controlled climatic factors. Results The untargeted metabolomics dataset contained a total of 7274 deconvolved retention time-m/z pairs across both electrospray ionisation (ESI) positive and negative polarities, from which 549 metabolites were identified or minimally annotated based upon accurate mass MS. Conventional principal component analysis (PCA) in combination with the Friedman significance test were applied to first identify which metabolites responded to temperature in a linear fashion. Multi-block hierarchical PCA in combination with the Friedman significance test was secondly applied to identify metabolites that were responsive to different day length conditions. Temperature had significant effect on a total of 365 metabolites representing a diverse range of chemical classes. It was observed that ripening of the blackcurrant berries under ambient conditions, compared to controlled conditions, resulted in an increased accumulation of 34 annotated metabolites, mainly anthocyanins and flavonoids. 18 metabolites were found to be regulated differentially under the different daylength conditions. Moreover, based upon the most abundant anthocyanins, a comparison between targeted and untargeted analyses, revealed a close convergence of the two analytical methods. Therefore, the study not just illustrates the value of non-targeted metabolomics approaches with respect to the huge diversity and numbers of significantly changed metabolites detected (and which would be missed by conventional targeted analyses), but also shows the validity of the non-targeted approach with respect to its precision compared to targeted analyses. Conclusions Blackcurrant maturation under controlled ambient conditions revealed a number of insightful relationships between environment and chemical composition of the fruit. A prominent reduction of the most abundant anthocyanins under the highest temperature treatments indicated that blackcurrant berries in general may accumulate lower total anthocyanins in years with extreme hot summer conditions. HPLC–PDA–MS metabolomics is an excellent method for broad analysis of chemical composition of berries rich in phenolic compounds. Moreover, the experiment in controlled phytotron conditions provided additional knowledge concerning plant interactions with the environment.
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The predicted and ongoing climate warming is expected to affect many aspects of plant development. We analysed data from a 31-year series of observations (1985–2016) on spring phenology and flowering and fruiting performance of three plum cultivars in an experimental orchard at Ås in southeast Norway (59° 40′N; 10° 50′E). Regression analyses revealed a trend of increasing March and April temperature during the study period that was highly significantly (P < 0.001) negatively correlated with the date of full bloom (FB). On average for all cultivars, blooming was advanced by 10 days over the study period. August and September temperature, which also increased significantly during the study period, was closely positively correlated with the amount of flowering in the subsequent spring and also interacted with early spring temperature in advancing blooming time. Investigation of the time of floral initiation in two of the studied plum cultivars revealed that the transition to reproductive development took place in early to mid-August. This finding strongly suggests that the close positive correlation between August-September temperature and the amount of flowering in plum observed in this and other studies, is causally linked to a specific physiological effect of elevated temperature on the flower bud formation process. Increasing March and April temperatures during the last 30 years has advanced blooming and spring phenology in plum and the resulting extension of the growing season has led to increasing fruit size at harvest. We conclude that so far, the ongoing climate warming appears to have been positive for plum production in the cool Nordic environment. However, an increasing risk of frost associated with earlier blooming will represent a potential negative effect of continued warming.
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Flowering performance and phenology of six new pear cultivars of Nordic origin were examined during a 12 year period. The seasonal timing of shoot growth and flower initiation were monitored in three years. The morphological floral stages of the flower bud formation process were examined for the cultivar ‘Celina’. Seven floral stages were identified and described. The date of full bloom varied between years as a function of the currently accumulated heat sum in early spring. Still, the earliness ranking of the cultivars was consistent across years for both flower initiation and blooming. The cultivars ‘Anna’ and ‘Ingeborg’ consistently initiated floral primordia 2–3 weeks earlier than ‘Celina’, ‘Clara Frijs’, ‘Fritjof’ and ‘Kristina’, and this was accompanied with 4–5 days earlier blooming in the following spring. The early flower initiation cultivars ‘Anna’ and ‘Ingeborg’ also had richer flowering than the late-blooming cultivars. ‘Fritjof’ was identified as a suitable pollinator for ‘Celina’ in the Nordic climate. Comparison of the flowering phenology of pear and apple cultivars showed that while the pears, on average, flowered a week ahead of the apples, they initiated flower primordia almost two weeks later, thus rendering the intervening period approximately three weeks longer in pear than in apple
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We grew young sweet cherry (Prunus avium L.) trees under controlled temperature and natural summer daylight conditions in order to study the control of flowering of the species. Two experiments with the cultivars ‘Lapins’ and ‘Van’, were conducted and compared with field results with the same cultivars at Ås in southeast Norway (59° 40′N, 10° 50′E, 90 m a.s.l.). Shoot growth increased with increasing temperature in the 12–21 °C range, but ceased in late summer (August) regardless of temperature conditions. A marked drop in temperature always induced an immediate cessation of growth. Under field conditions at Ås, both growth cessation and floral initiation took place by about 1 August. Low temperature (12–15 °C) significantly enhanced flowering of both cultivars compared with 21 °C, which tended to depress flower bud formation during the summer but stimulated the subsequent flower differentiation process. These results concur with earlier regression analyses, which revealed a close positive correlation between historical records of sweet cherry yields over a 40-year period in farmer’s fields in the fjord districts of western Norway and previous year August-September temperature, and a negative correlation with previous year July temperature. Practical implications of the results are discussed and it is suggested that inadequate temperature control in rain-protected cultivation in plastic tunnels might have negative consequences for next year’s flowering and yield.
Abstract
The aim of the investigation was to assess and compare the environmental limits for growth cessation and floralinitiation in a range of new and established biennial-fruiting red raspberry (Rubus idaeus L.) cultivars of diverseorigin under phytotron and field conditions. The results confirmed that growth cessation and floral initiation inbiennial-fruiting red raspberry are jointly controlled by the interaction of low temperature and short days (SD).When transferred from non-inductive high temperature and long day (LD) conditions to naturally decreasingautumn daylengths at varying phytotron temperatures on 18 August, growth immediately levelled off and ceasedcompletely within 2 weeks in all cultivars at 9 °C. Serial dissections of lateral buds revealed that floral initiationsimultaneously took place. At 15 °C on the other hand, the plants continued growing and remained vegetativeuntil around 15 September when the daylength had decreased to approximately 13 h. The change to 9 °C resultedin an immediate but short-lasting floral induction response that did not bring about initiation in buds situatednear the base of the canes, as was the case at 15 °C. At 18 °C, marginal floral induction took place only in thecultivars ‘Glen Ample’, ‘Balder’ and ‘Vene’, even at photoperiods down to 10 h, whereas at 21 °C, all cultivarsgrew vegetatively regardless of daylength conditions. However, exceptions were some plants of ‘Vene’ and‘Anitra’ that initiated terminal flowers at 18 and 21 °C and flowered directly without chilling (so-called tipflowering). Although some cultivars of Northern origin ceased growing and initiated floral primordia somewhatearlier (at longer photoperiods) than those of more southerly origin, the differences were relatively minor andnot consistent (no latitudinal cline). Results obtained in the field under decreasing autumn temperature anddaylength conditions agreed closely with the results in the phytotron. We therefore conclude that results ob-tained with raspberry in properly controlled daylight phytotron experiments are generally applicable to fieldconditions.
Abstract
Effects of annual versus biennial cropping with varying shoot densities on plant structure, berry yield and quality were studied in ‘Glen Ample’ raspberry over a period of four seasons (two cropping years). In the vegetative phase, primocane height and internode length were larger in the annual than in the biennial cropping system. These parameters as well as Botrytis infestation increased with increasing shoot density. In both cropping years, berry yields per unit area were about 20% higher in the biennial cropping system, whereas yields per shoot were not significantly different in the two systems. In both cropping systems, yields per shoot strongly declined with increasing shoot density, while yields per metre row increased slightly. Regardless of cropping system, yields per metre row did not increase with increasing shoot density beyond eight shoots per metre. The concentrations of dry matter, soluble solids, titratable acidity and ascorbic acid as well as the intensity of juice colour all declined with increasing shoot density. We conclude that under controlled shoot density conditions, there is little scope for biennial yield increases that fully compensates for the lost crops every second year. However, the system greatly facilitates berry harvest and eases plant disease pressure.
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The effect of controlled nutrient feeding during the period of short day (SD) induction of flowering has been studied in three SD berry crops. An experimental system with standardized plant material grown with trickle fertigation in controlled environments was used. In strawberry, flowering was advanced and increased when an additional N pulse was given 1-2 weeks after commencement of a 4-week SD induction period, while the opposite resulted when the treatment was applied 2 weeks before start of SD. In blackcurrant, the highest flowering and yield were obtained when fertilization was applied shortly after the natural photoperiod had declined to the inductive length in September. While generous nutrient supply during spring and summer reduced berry soluble solids in blackcurrant, this was not observed with autumn fertilization. Autumn fertilization did not adversely affect plant winter survival or growth vigour in spring. Withdrawal of fertilization prior to, or at various stages during floral induction, did not significantly affect flowering and yield in raspberry, but marginally advanced flowering and fruit ripening.
Authors
Anita SønstebyAbstract
No abstract has been registered
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We examined the influence of fertigation on vegetative and generative parameters of strawberry plants (Fragaria × ananassa Duch.) and evaluated rapid analysing tools for N and K in leaf tissue. The experiments were undertaken in an open polytunnel on “table top” with ‘Sonata’ and ‘Korona’ grown in 2-L pots filled with a peat-based soil mixture. The experimental design was a randomized plot with three replications. Plants were fertigated with EC levels of 0.5, 1.0, 1.5 and 2.0 mS cm-1, based on two stock solutions of 7.5 kg YaraLiva™ Calcinit and 7.5 kg Kristalon™ Indigo, both dissolved in 100 L of water. Percentage N and K in leaves differed between analysing methods, cultivars, EC and date. We found interactions between the cultivar and EC level and between date and cultivar for N and K in leaf. Analysing NO3- by a photometric method (PM) in a lab, and by Laqua twin (LT), showed significant interaction with N% of leaf dry matter (DM) only for LT (r2=0.36). N% increased with higher EC level, more for ‘Korona’ than for ‘Sonata’. LT K+ did not correlate with K% (r2=0.014). The number of crowns and runners increased for both cultivars up to EC 1.5, while the number of leaves was unaffected. Petioles were the shortest at the lowest EC. Flower initiation was earlier at low EC in both cultivars. In the following spring, the time to flowering and first harvest was reduced with the decreasing EC. The number of flowers per plant increased up to EC 1.5, but dropped strongly at EC 2.0 for ‘Korona’, while ‘Sonata’ had a gradual increase of flowers with the increasing EC, but the number was only a third of ‘Korona’, except at EC 2.0, where the amount was equal for both cultivars. The conclusion can be drawn that LT correlated better than ChlDualex with N in strawberry leaves. However, r2 was only 0.36 indicating that LT NO3- is a coarse management tool. LT K+ was not a promising tool for rapid K+ test in these experiments. ‘Korona’ seemed to benefit of higher N levels for both vegetative growth and generative development than ‘Sonata’ up to EC 1.5, but ‘Sonata’ reached a higher floral primordia development stage in early October.
Authors
Inger Martinussen Tomasz Leszek Woznicki Unni Myrheim Roos Anita Sønsteby Eivind Uleberg Anne Linn HykkerudAbstract
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Authors
Inger Martinussen Tomasz Leszek Woznicki Unni Myrheim Roos Anita Sønsteby Eivind Uleberg Anne Linn HykkerudAbstract
No abstract has been registered
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Anita SønstebyAbstract
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Anita SønstebyAbstract
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Anita SønstebyAbstract
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Authors
Elli A. Koskela Takeshi Kurokura Tuomas Toivainen Anita Sønsteby Ola M Heide Daniel J. Sargent Sachiko Isobe Laura Jaakola Hrannar Hilmarsson Paula Elomaa Timo HytönenAbstract
• Vernalisation requirement is an agriculturally important trait that postpones the development of cold-sensitive floral organs until the spring. The family Rosaceae includes many agriculturally important fruit and berry crops that suffer from crop losses caused by frost injury to overwintering flower buds. Recently, a vernalisation-requiring accession of the Rosaceae model woodland strawberry (Fragaria vesca) has been identified in northern Norway. Understanding the molecular basis of the vernalisation requirement in this accession would advance the development of strawberry cultivars better adapted to temperate climate. • We use gene silencing, gene expression analysis, genetic mapping and population genomics to study the genetic basis of the vernalisation requirement in woodland strawberry. • Our results indicate that the woodland strawberry vernalisation requirement is endemic to northern Norwegian population, and mapping data suggest the orthologue of TERMINAL FLOWER1 (FvTFL1) as the causal floral repressor. We demonstrate that exceptionally low temperatures are needed to downregulate FvTFL1 and to make these plants competent to induce flowering at low postvernalisation temperatures in the spring. • We show that altered regulation of FvTFL1 in the northern Norwegian woodland strawberry accession postpones flower induction until the spring, allowing plants to avoid winter injuries of flower buds that commonly occur in temperate regions.
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BACKGROUND: It is questioned if Norwegian nurseries can compete with the continental nursery industry in an open market. OBJECTIVE: Investigated how quality of certified Norwegian strawberry transplants, developed and yielded from planting to first cropping year. METHODS: Plant qualities of Norwegian fresh and cold stored bare root- and plug-plants of ‘Korona’ and ‘Sonata’ were examined for establishing and yield parameters in the open, after three intervals of planting. Fresh plug-plants were delivered when available. Trials were established at NIBIO Research Station Kvithamar, Norway. Growth and yield parameters were registered in the establishing and cropping years. RESULTS: Plant establishment was poor in 2013 compared with 2014. Bare-root plants stored at 2–4°C generally developed poorly. Plug-plants established well at all delivery dates, except fresh plug in one year. Development of runner plants depended on plant type, cultivar and year. Plug- and bare root-plants planted immediately after first delivery generally developed best crowns. Primary flower primordia reached a more developed stage for ‘Sonata’ than for ‘Korona’. Fruit yield of bare root was low in the establishing years. Plant-types differed in yield and fruit weight between cropping years. CONCLUSIONS: Bare-root and plug- plants planted one day after delivery generally yielded best. Storage of bare-root plants generally reduced yield. Fresh plug plants had low yield when planted late. Fruit yield of A15 and A13 in the establishing year was not satisfactory.
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Plants of six strawberry cultivars were raised under controlled conditions and tested for flowering and yield potential. Short days (SD) at intermediate temperatures for 4 weeks in August induced profuse flowering in subsequent long days (LD) in all cultivars except the late-flowering ‘Malwina’. LD conditions induced flowering only in ‘Nobel’, which has an everbearing parent. ‘Nobel’ and ‘Saga’ exhibited broad temperature adaptation for SD floral induction, which was generally reduced or suppressed at 9 and 27°C. After autumn planting, all cultivars flowered most abundantly in plants raised in SD and intermediate temperatures. Flowering was earliest in ‘Nobel’ and ‘Rumba’. Plants that did not reach floral commitment after 4 weeks in SD continued and completed induction under subsequent natural SD conditions after planting in the field, demonstrating the capability of fractional induction. Berry yield varied in parallel with flowering in the field and was always higher in plants raised under SD conditions. The traditional cultivars ‘Florence’ and ‘Sonata’ out-yielded the more recent cultivars. Some cultivars lost more than two thirds of their initiated flowers during the winter with obvious consequences for their yields. With proper raising management, acceptable yields were obtained after autumn planting even in a cool Nordic climate.
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Authors
Tomasz Leszek Woznicki Anita Sønsteby Kjersti Aaby Berit Karoline Martinsen Ola M. Heide Anne-Berit Wold Siv Fagertun RembergAbstract
BACKGROUND Marked effects of the climatic environment on fruit chemical composition have often been demonstrated in field experiments. However, complex covariations of several climatic factors in the natural environment complicate the interpretation of such experiments and the identification of the causal factors. This can be better achieved in a phytotron where the various climatic factors can be varied systematically. Therefore, we grew four black currant cultivars of contrasting origin in a phytotron under controlled post-flowering temperature and photoperiod conditions and analysed the berries for their ascorbic acid, sugar and organic acid contents. RESULTS The analyses revealed significant effects of genotype on all investigated compounds. Particularly large cultivar differences were observed in the concentrations of l-ascorbic acid (AA) and sucrose. The concentrations of both AA and dehydroascorbic acid (DHAA), as well as the concentrations of all major sugars, decreased consistently with an increasing temperature over the temperature range 12–24 °C. Fructose and glucose were the predominant sugars with concentrations several fold higher than that for sucrose. AA was the main contributor to the total ascorbate pool in black currant berries. The AA/DHAA ratio varied from 5.6 to 10.3 among the studied cultivars. The concentration of citric acid, which was the predominant organic acid in black currant berries, increased with an increasing temperature, whereas the opposite trend was observed for malic and shikimic acid. Quninic acid was always present at relatively low concentrations. By contrast, photoperiod had no significant effect on berry content of any of the investigated compounds. CONCLUSION It is concluded that the post-flowering temperature has marked effects on the concentration of important chemical compounds responsible for taste and nutritional value of black currant berries, whereas photoperiod has no such effect in the studied cultivars. © 2016 Society of Chemical Industry
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Black currant is a woody plant in which growth and development are intimately controlled by, and synchronised with seasonal changes in photoperiod and temperature. Concern over the potential impact of global warming on plant phenology and yield, led us to initiate relations. An experimental system with single-stemmed potted plants was developed which allowed a research program to address both qualitative and quantitative assessment of climatic responses. Growth cessation and flowering were both induced by short days, with critical photoperiods of approximately 17 and 16 h, respectively, for most cultivars. Both processes were advanced and promoted by increasing autumn temperature with an optimum in the 18-21°C region. An exception was cultivars of high-boreal origin, which had an early growth cessation at low temperature. Unexpectedly, however, not all plants flowered after exposure to 10 h photoperiod, and the number of flowers decreased as the photoperiod was reduced from the near-critical length of 15 h. This was due to premature dormancy induced by an abrupt change to photoperiods well below the critical level. Field experiments revealed that cultivars of varying geographic origin, exhibited a typical latitudinal cline in their photoperiodically controlled timing of growth and flowering responses. Breaking of bud dormancy and promotion of flower bud development required chilling at -5°C for 14 weeks or more for optimal responses. However, while chilling at -10°C for 8 weeks resulted in dormancy release, continued chilling to 16 weeks inhibited bud break completely. We therefore propose that excessive chilling induces secondary bud dormancy in black currant. The observed high chilling requirements of black currants concur with the reported vulnerability of this crop to declining winter chill in the wake of the ongoing global warming. Furthermore, such conditions also induce a particularly deep bud dormancy state that further increases the chilling need.
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The paper is a mini review on the climatic effects on berry production and berry quality in the Arctic north. Plants in the north are facing short growing seasons with low temperatures and long days with a unique light quality. The winter time is cold but with fluctuating temperatures, especially along the coast. Fluctuating winter temperatures and unstable snow cover is a challenge for the perennials that need to be dormant during winter time. Dormancy is induced in the autumn by a combination of day length and temperature. The wild berries domestic to the Nordic countries are adapted to these growth conditions while many of the commercially important berry species originate from more southern areas. Pre-breeding studies on interactions between genotype and environment are essential in order to develop climatically adapted berry cultivars for northern growth conditions.
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The effect of fertility status and temperature conditions during floral induction on flowering, berry yield,and weight and drupelet numbers of individual berries were studied in ‘Glen Ample’ raspberries grownunder controlled conditions. Withdrawal of normal fertilization prior to and at various stages duringfloral induction did not affect yield and berry size, but marginally advanced flowering and fruit ripening.The successive stages of floral initiation and differentiation were studied and identified by scanning elec-tron microscopy of the uppermost lateral buds of plants grown for six weeks under naturally decreasingautumn photoperiods at temperatures of 9, 15 and 21◦C. Low temperature advanced floral initiation, andadvanced and enhanced flowering and berry yield in the following season. However, at variance fromearlier studies, the plants eventually initiated flower primordia even at 21◦C. Marginal low temperatureand short day conditions during the last days before the temperature treatments were started on 17September might possibly have reduced the subsequent induction requirements enough to explain thisunexpected result. Correlation analyses revealed an over-all positive correlation between fruit weightand drupelet numbers (r = 0.568, P = 0.01). In berries from the early harvests, the number of drupelets perberry increased with decreasing temperature, while the numbers converged to the same level regardlessof temperature in the later harvests. Based on the progress of the floral initiation process at the vari-ous temperatures, we interpret this to mean that only the early initiated flowers, that gave rise to theearly maturing berries, were differentiated during the actual period of controlled temperature exposure,whereas the remaining flowers were differentiated afterwards when all plants were exposed to identicallow temperature conditions. Increased femaleness under optimal floral induction conditions is in agree-ment with results in both monoecious and dioecious plants and circumstantial evidence suggest that,in the raspberry, this might be mediated by changes in gibberellin activity which acts as a male sexualhormone in plants and is known to inhibit growth cessation and floral initiation in raspberry.
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Berry yield and chemical composition of four commercial black currant cultivars were recorded in a field experiment in Norway over an 8-year period and related by linear regression analysis to temperature and precipitation conditions prevailing during the May-July preharvest period. Highly significant differences between cultivars and among years were found for all measured parameters. Fruit dry matter, soluble solids and pH were positively correlated with temperature and negatively correlated with precipitation during May-July, while yield, berry weight, and the concentration of total phenols and ascorbic acid showed the opposite relationship, being highly negatively correlated with temperature and positively correlated with precipitation. Similar black currant experiments elsewhere in Europe have often given deviating results, varying from opposite to no effects of the same weather variables, suggesting that fruit composition is influenced by several interacting genetic and environmental parameters. We conclude that differences in local weather and soil conditions and the use of different cultivars complicate direct comparison of such field experiments. Nevertheless, the observed strong and opposite correlations with precipitation and temperature suggest an inherently low drought tolerance of black currant plants.
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In order to investigate the relationship between environmental conditions and vegetative growth and reproductive development in the strawberry, freshly rooted runner plants of the cultivar ‘Sonata’ were grown in a phytotron at temperatures of 12, 18 and 24 °C and photoperiods of 10 h short day (SD) and 20 h long day (LD) for 31 d and harvested at 10 d intervals. Plant dry weight and leaf area increases were exponential versus time, giving a linear regression with the natural log (ln). This rendered the relative growth rate (RGR) constant over time at each environmental condition. Over the entire 31 d growth period, the RGR increased linearly with increasing temperature across the range of temperatures with a further 10–13% enhancement by LD. A maximum RGR value of 0.077 g/g/d was determined in LD at 24 °C. Increases in the RGR was driven by a combined increase in net assimilation rate (NAR) and leaf area ratio (LAR) and was associated with an increased allocation of dry matter production into leaves and less into crowns and roots. Because of this, the shoot/root ratio increased consistently with increasing temperature and photoperiod, which was also associated with a significant increase in the tissue C/N concentration ratio. Low temperature promoted starch accumulation markedly in all parts of the plants, with a further enhancement by LD conditions, while the concentrations of soluble sugars were less affected by the climatic environment. Forcing of plants exposed to the various growth conditions for 31 d showed that all plants at 12 and 18 °C and 80% of those at 24 °C had initiated flowers in SD, whereas none had initiated flowers in LD regardless of temperature conditions. All these results demonstrate an opposite environmental relationship between vegetative growth and reproductive development in the strawberry.
Authors
Tomasz Leszek Woznicki Kjersti Aaby Anita Sønsteby Ola M. Heide Anne-Berit Wold Siv Fagertun RembergAbstract
The effects of postflowering temperature and daylength on the concentration of individual phenolic compounds were studied in black currant (Ribes nigrum L.) berries under controlled phytotron conditions. The four cultivars studied varied greatly in their concentrations of individual phenolic compounds and temperature stability for accumulation. The concentrations of a wide range of identified phenolic compounds were strongly influenced by temperature over the 12–24 °C range, often with opposite temperature gradient patterns for compounds within the same subclass. Accumulation of anthocyanins and flavonols increased under natural long day conditions, which provided an increased daily light integral, while under identical light energy conditions, photoperiod had little or no effect on the concentration of phenolic compounds. Furthermore, with the exception of members of the hydroxycinnamic acid subclass, the concentration of most phenolic compounds was higher in berries ripened outdoors than in the phytotron, apparently due to screening of UV-B radiation by the glass cover.
Abstract
As part of an overall assessment of the commercial suitability of strawberry cultivars for the Nordic environment, we studied 13 diverse cultivars in an experimental field in South East Norway. Early-maturing cultivars were characterized by early initiation of floral primordia and early flowering and fruit maturation. High temperatures in July and early August delayed floral initiation in the early cultivars, resulting in more synchronous initiation of early and late cultivars. The recent Norwegian cultivar ‘Nobel’, which has an everbearing parent, differed from the other cultivars by early initiation also at elevated summer temperature. Inadequate yield and berry size were identified as important causes for outdating of older cultivars, such as ‘Senga Sengana’ and ‘Glima’. Overall, the high-yielding and large-fruited ‘Sonata’ was judged as the best fresh consumption cultivar in Norway, and market trends indicate that it will continue to expand its market share at the expense of ‘Korona’, mainly because of inadequate fruit firmness and shelf life of the latter. Adequate yields and berry quality justify the use of the late maturing ‘Florence’ for prolongation of the fresh market season. The results are discussed together with practical experiences and market preferences in an attempt to provide overall cultivar recommendations for Norway.
Authors
Elli Aurora Koskela Anita Sønsteby Henryk Flachowsky Ola M. Heide Magda-Viola Hanke Paula Elomaa Timo HytönenAbstract
The effects of daylength and temperature on flowering of the cultivated octoploid strawberry (Fragaria × ananassa Duch.) have been studied extensively at the physiological level, but information on the molecular pathways controlling flowering in the species is scarce. The flowering pathway has been studied at the molecular level in the diploid short-day woodland strawberry (F. vesca L.), in which the FLOWERING LOCUS T1 (FvFT1)–SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (FvSOC1)–TERMINAL FLOWER1 (FvTFL1) pathway is essential for the correct timing of flowering. In this work, we show by transgenic approach that the silencing of the floral repressor FaTFL1 in the octoploid short-day cultivar ‘Elsanta’ is sufficient to induce perpetual flowering under long days without direct changes in vegetative reproduction. We also demonstrate that although the genes FaFT1 and FaSOC1 show similar expression patterns in different cultivars, the regulation of FaTFL1 varies widely from cultivar to cultivar and is correlated with floral induction, indicating that the transcription of FaTFL1 occurs at least partially independently of the FaFT1–FaSOC1 module. Our results indicate that changing the expression patterns of FaTFL1 through biotechnological or conventional breeding approaches could result in strawberries with specific flowering and runnering characteristics including new types of everbearing cultivars.
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Adam Vivian-Smith Jørn Henrik Sønstebø Thomas Marcussen Eivind Uleberg Julie Graham Anita Sønsteby Inger MartinussenAbstract
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Jon Anders Stavang Sabine Freitag Alexandre Foito Susan Verrall Ola M. Heide Derek Stewart Anita SønstebyAbstract
In order to identify the optimal harvest time and monitor changes in raspberry (Rubus idaeus L. cv. Glen Ample) fruit quality during ripening and storage, quality was assessed and compared by physical, chemical and sensory fruit quality criteria. Visual classification of fruit colour according to the Natural Colour System (NCS) chart and by physical measurement of fruit adherence to the receptacle or fruit compression resistance yielded parallel and highly significant results. The light red colour stage corresponding to NCS S code 3060-Y90R was identified as the optimal harvest stage for commercial fresh marketing of the ‘Glen Ample’ cultivar. Fruit harvested at this stage developed the same chemical and sensory qualities as in situ matured fruits and maintained high sensory quality after 8 days of storage in the dark at 2–3 °C. As the fruits mature, the concentration of titratable acids decreases, whereas the concentrations of anthocyanins and the sugar:acid ratio increase in parallel with colour development. While correlation analysis revealed a correlation between sensory traits like sweetness and acidity with sucrose and the sugar:acid ratio, respectively, the overall fruit tastefulness was not strongly correlated with any specific phytochemical component, thus illustrating the complex nature of this sensory trait. Due to its ease of performance, picking raspberry fruits related to a standardised colour chart is recommended for picking raspberry fruits with optimal quality.
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Sebastian Mazur Anita Sønsteby Arnfinn Nes Anne-Berit Wold A. Foito S Freitag Susan Ramsey Verrall Derek Stewart Ola M. HeideAbstract
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Sebastian Mazur Anita Sønsteby Anne-Berit Wold A. Foito S Freitag S. Verrall S. Conner Derek Stewart Ola M. HeideAbstract
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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.
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Jahn Davik Gage Koehler Britta From Torfinn Torp Jens Rohloff Petter Eidem Robert Wilson Anita Sønsteby Stephen K, Randall Muath Alsheikh-YousefAbstract
The use of artificial freezing tests, identification of biomarkers linked to or directly involved in the low-temperature tolerance processes, could prove useful in applied strawberry breeding. This study was conducted to identify genotypes of diploid strawberry that differ in their tolerance to low-temperature stress and to investigate whether a set of candidate proteins and metabolites correlate with the level of tolerance. 17 Fragaria vesca, 2 F. nilgerrensis, 2 F. nubicola, and 1 F. pentaphylla genotypes were evaluated for low-temperature tolerance. Estimates of temperatures where 50 % of the plants survived (LT50) ranged from −4.7 to −12.0 °C between the genotypes. Among the F. vesca genotypes, the LT50 varied from −7.7 °C to −12.0 °C. Among the most tolerant were three F. vesca ssp. bracteata genotypes (FDP821, NCGR424, and NCGR502), while a F. vesca ssp. californica genotype (FDP817) was the least tolerant (LT50 −7.7 °C). Alcohol dehydrogenase (ADH), total dehydrin expression, and content of central metabolism constituents were assayed in select plants acclimated at 2 °C. The LT50 estimates and the expression of ADH and total dehydrins were highly correlated (r adh = −0.87, r dehyd = −0.82). Compounds related to the citric acid cycle were quantified in the leaves during acclimation. While several sugars and acids were significantly correlated to the LT50 estimates early in the acclimation period, only galactinol proved to be a good LT50 predictor after 28 days of acclimation (r galact = 0.79). It is concluded that ADH, dehydrins, and galactinol show great potential to serve as biomarkers for cold tolerance in diploid strawberry.
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Gage Koehler Jens Rohloff Robert Wilson Per Winge Anita Sønsteby Muath Alsheikh Stephen K, RandallAbstract
There is limited research about variations between cultivars for freezing tolerance in fruit crops and indeed much less is known about the distinctive in ground structure of the crown that herbaceous perennials depend on for regeneration in spring. Because strawberry is a representative species for the Rosaceae crops knowledge gained is expected to be transferrable to benefit improvement of many of these related crops. To gain insight into the molecular basis that may contribute to overwintering hardiness, a comparative proteomic analysis was carried out for four Fragaria x ananassa (octoploid strawberry) cultivars that differ in freezing tolerance. Protein expression was investigated in the overwintering relevant crown structure of strawberry from plants exposed to 0, 2, and 42 day cold treatments and were examined by two-dimensional gel electrophoresis (2D). Some proteins, such as molecular chaperones, antioxidants / detoxifying enzymes, metabolic enzymes, and pathogenesis related proteins were revealed to be at significantly higher levels before cold exposure in the most freezing tolerant cultivars, (‘Jonsok’ and ‘Senga Sengana’) compared to the least tolerant cultivars (‘Frida’ and ‘Elsanta’). Freezing tolerance was evaluated for the cultivars before and after cold exposure, with findings that support that the most freezing tolerant cultivars are poised for rapid adaptation to cold exposure, suggesting potential differences in capacity or rate for cold acclimation. Thus, the molecular basis for enhanced overwintering survival may be related to the elevated basal level of a number of proteins, many of which are known to confer stress tolerances. These findings are presented and overlaid with a LFQP shotgun analysis and microarray analysis. This study presents the largest quantitative proteomic data-set for strawberry crown tissue during cold exposure to date. Through the comparison of these cultivars that differ in freezing tolerance, proteins that may contribute to cold tolerance but lack significant cold induction were revealed.
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Authors
Muath Alsheikh-Yousef Gage Koehler Robert Wilson Jens Rohloff Anita Sønsteby Jahn Davik Stephen K, RandallAbstract
A crucial consideration for strawberry producers in Norway and other northern countries is winter freezing damage. A long-term goal of the Norwegian strawberry breeding is to increase winter hardiness and to improve fruit quality. Due to the complexity involved in regulating and enhancing freezing tolerance, the progress in the improvement of cultivars using traditional screening methods have had limited success. Thus, the development of molecular markers for freezing hardiness would facilitate the selection work for this trait. In this effort, we have developed and adopted state-of-art molecular tools to investigate cold response in strawberry plants during the acclimation phase resulting in the identification of a large number of genes, proteins, and distinct metabolites that correspond to cold/freezing tolerance in strawberry. To identify proteins responsible for freezing tolerance in strawberry we have examined alterations in protein levels in strawberry varieties that differ in cold tolerance using either 2-DE gel analysis followed by LC-MS/MS analysis or a shotgun MS/MS approach. Proteomic analysis suggested 30 potential biomarkers that showed significant changes in the cultivated strawberry in response to cold. In addition, GC-MS-based metabolite profiling revealed the up-regulation of carbohydrates, polyols, amino acids, TCA intermediates, and other distinct secondary metabolites after cold treatment. Transcriptional analysis of the cold acclimated samples also confirmed the regulation upon cold-treatment with varietal differences in strawberry. Moreover, several F2-populations from the model F. vesca parents diverging in cold tolerance have been developed in order to facilitate mapping of QTLs by performing GBS analyses. The knowledge attained from these endeavors is expected to expedite breeding of strawberries to achieve freezing tolerant lines and provide an integrative understanding of the molecular pathways that underlie this characteristic. * Rohloff et al. (2012) Metabolite profiling reveals novel multi-level cold responses in the model Fragaria vesca. Phytochemistry 79:99-109. * Koehler et al. (2012) Proteomic study of low temperature responses in strawberry cultivars (Fragaria x ananassa) that differ in cold tolerance. Plant Physiology 159:1787–1805 * Davik et al., (2012) Low temperature tolerance in diploid strawberry species (Fragaria ssp.) and its correlation to alcohol dehydrogenase levels, dehydrin levels, and central metabolism constituents. Planta (in press; DOI: 10.1007/s00425-012-1771-2).
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Authors
Gage Koehler Robert Wilson John V. Goodpaster Anita Sønsteby Xianyin Lai Frank A. Witzmann Jin-Sam You Jens Rohloff Stephen K, Randall Muath Alsheikh-YousefAbstract
To gain insight into the molecular basis contributing to overwintering hardiness, a comprehensive proteomic analysis comparing crowns of Fragaria × ananassa (octoploid strawberry) cultivars that differ in freezing tolerance was conducted. Four cultivars were examined for freeze tolerance and the most cold-tolerant cultivar (‘Jonsok’) and least tolerant cultivar (‘Frida’) were compared with a goal to reveal how freezing tolerance is achieved in this distinctive overwintering structure and to identify potential cold-tolerance associated biomarkers. Supported by univariate and multivariate analysis, a total of 63 spots from 2DE analysis and 135 proteins from label-free quantitative proteomics (LFQP) were identified as significantly differentially expressed in crown tissue from the two strawberry cultivars exposed to 0, 2, and 42 day cold treatment. Proteins identified as cold tolerance associated included molecular chaperones, antioxidants/detoxifying enzymes, metabolic enzymes, pathogenesis related proteins and flavonoid pathway proteins. A number of proteins were newly identified as associated with cold tolerance. Distinctive mechanisms for cold tolerance were characterized for two cultivars. In particular, the ‘Frida’ cold response emphasized proteins specific to flavonoid biosynthesis, while the more freezing tolerant ‘Jonsok’ had a more comprehensive suite of known stress responsive proteins including those involved in antioxidation, detoxification, and disease resistance. The molecular basis for ‘Jonsok’ enhanced cold tolerance can be explained by the constitutive level of a number of proteins that provide a physiological stress-tolerant “poise”.
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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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Earliness, fruit yield and quality of six annual-fruiting raspberry (Rubus idaeus L.) cultivars were tested under protected cultivation in a cool Nordic environment. After raising plants for 5 weeks in greenhouses with average mean temperatures of 20 degrees C, 22 degrees C, or 26 degrees C, the plants were cropped in an open plastic tunnel at latitude 61 degrees N. The highest yielding cultivars were 'Autumn Bliss' and 'Polka', with 640 g plant(-1). Overall, the most promising cultivar was 'Polka' which combined high yield with large fruit of good flavour and firmness. In earliness, 'Polka' was surpassed only by 'Autumn Bliss', which confirmed its position as the earliest commercial annual-fruiting cultivar. However, 'Autumn Bliss' had soft fruits with little flavour and a short shelf-life, which greatly reduced the potential of the cultivar for the fresh fruit market. The later ripening cultivar 'Erika' did not complete its crop under these conditions, but its large unrealised yield potential and good fruit quality rendered it extremely promising for environments with a longer growing season. 'Sugana' was late, with low yields and poor fruit quality, while 'Marcela' did not yield enough fruit to be of interest under the present conditions. High temperatures during the 5-week raising period generally advanced flowering and fruit ripening in all cultivars, with the notable exception of 'Autumn Treasure' in which flowering was suppressed and strongly delayed by high temperature. Under the present conditions, there was a highly positive correlation between earliness and fruit yield. Regression analyses identified a low number of dormant buds as the single most important component of plant architecture associated with high fruit yield, accounting for 47% of the total variation.
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The effects of postflowering temperature on the fruit chemical composition of Glen Ample raspberries were studied under controlled environment conditions. The berry weight decreased significantly with increasing temperature (12, 18, and 24 degrees C) and with progress of the harvest period. Because the moisture content increased in parallel with the berry weight, the antioxidant capacity (AOC) and the concentration of a range of bioactive compounds decreased with decreasing temperature and progress of the harvest season when expressed on a fresh weight basis in the conventional way. Under those circumstances, dry weight units are therefore preferable. However, despite the dilution effect of large berries, the concentration of ascorbic acid (vitamin C) increased with decreasing temperature, even on a fresh weight basis. Berry AOC was closely correlated with total phenolic concentration (r = 0.958), predominantly anthocyanins and ellagitannins. While a total of 10 anthocyanins were detected, cyanidin-3-sophoroside and cyanidin-3-(2(G)-glucosylrutinoside)-rutinoside accounted for 73% of the total, the former decreasing and the latter increasing with increasing growth temperature. By far, the most prevalent ellagitannins were lambertianin C and sanguiin H-6, both of which increased significantly with increasing temperature. It is concluded that the growth temperature has significant and contrasting effects on the concentration of a range of potentially bioactive compounds in raspberry.
Abstract
Red raspberry (Rubus idaeus L.) is an economically important small fruit species, rich in antioxidants and other phytochemicals (Rao and Snyder, 2010). Most research in the area of screening the antioxidant activity in dietary plants have mainly been focused on variation among species and cultivars and effects of postharvest handling and storage (e.g. Kalt et al., 2002). Little is known about the impact of environmental factors such as temperature and light conditions. The use of plastic tunnels for out-of-season production of red raspberries has expanded production in Norway. This involves a change in climate environment which might influence the chemical composition of the fruits. Here we present the results of an investigation of temperature on fruit quality of red raspberry (Remberg et al., 2010).
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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.
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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.
Abstract
The effects of timing of nitrogen (N) fertilization relative to the beginning of a 4-week floral-inducing short-clay (SD) period have been studied in 'Korona' strawberry plants under controlled environment conditions. Groups Of low fertility plants were fertilized with 100 ml of calcium nitrate solution for 3 days a week for a period of 3 weeks starting at various times before and at the beginning of the SD period, as well as at different times during the SD period. All plants, including SD and long day (LD) control plants, received a weekly fertilization with a low concentration complete fertilizer Solution throughout the experiment. Leaf at-ea. fresh and dry matter increments of leaves, crowns and roots, as well as leaf chlorophyll concentration (SPAD Values) were monitored during the experimental period. A general enhancement of growth took place at all times of N fertilization. This was paralleled by an increase in leaf chlorophyll concentration, indicating that the control plants were in a mild state of N deficiency. When N fertilization was started 2 weeks before beginning of the SD period, flowering was delayed by 7 days, and this was gradually changed to an advancement of 8 days when the same treatment was started 3 weeks after the first SD. The amount of flowering was generally increased by N fertilization although the effect varied greatly with the time of N application. The greatest flowering enhancement Occurred when N fertilization started I week after the first SD when the number of flowering crowns and the number of inflorescences per plant were more than doubled compared with the SD control, while fertilization 2 weeks before SD had no significant effect on these parameters. Importantly, the total number of crowns per plant was not affected by N fertilization at any time, indicating that enhancement of flowering was not due to an increase in potential inflorescence sites. No flowering took place in the control plants in LD. Possible physiological mechanisms involved and practical applications of the findings are discussed. (C) 2009 Elsevier B.V. All rights reserved.
Abstract
In the Nordic strawberry industry only single-cropping cultivars are used. Several everbearing cultivars have been tried, but neither yield nor quality has been satisfactory. In 2005, new everbearing cultivars were collected and an experiment was established in a polyethylene tunnel. Yield and runnering capacity were recorded in two seasons. The cultivars were the English 'Flamenco' and 'Everest', the Dutch 'Elan' and the Norwegian 'Rita', 'Rondo', 'Ridder' and 'Rosa'. Plug plants were planted in double rows on low ridges mulched with plastic at a plant density equivalent to 50,000 plants per ha. A block design with 20 plants per plot and four replicates was used. The field was harvested two to three times a week during the whole season from June until the beginning of October in both years. Berry size was recorded at all harvests while taste and general performance were evaluated using a scale 1-9. In the first year, the everbearing cultivars had significantly higher yield than the single-cropping cultivars due to more inflorescences, but this was levelled out the second year. While the cropping season of the single-cropping cultivars is only about four weeks, the everbearing cultivars were picked from late June until beginning of October, in both years. The highest yields were obtained by 'Everest' (729 and 844 g) followed by 'Rita' and 'Ridder'. The cultivars 'Elan' and 'Rondo' scored highest both in taste and general performance. 'Everest' also performed well, but flavour was not acceptable.
Abstract
Techniques for the production of raspberry long canes with high yield potential were studied on a research station and in two commercial nurseries in South Norway. Potted 'Glen Ample' plants were grown in the open and in polyethylene greenhouses during two seasons in order to optimize Cultural practices. Dates of propagation and transfer to the production sites were varied. Following cold storage from December to early June, the canes were tipped (cut) at 160 cm height and grown in open plastic tunnels in the fruiting season for the evaluation of growth and yield performance. Remarkable berry yields of 1.5-3.8 kg per plant (cane) were regularly achieved. When grown in the open, later starts than June 1 (June 15 and July 1) successively reduced yields. On the other hand, an earlier start involves risks of growth cessation due to low spring temperature. When grown in greenhouses, high yields were still possible when plants were transferred from propagation conditions as late as July 1, although optimal yields of nearly 4 kg per plant were obtained with transfer on June 15. In a year with unusually high summer temperatures, the yields of canes produced in the open and in greenhouses did not vary significantly, whereas in the second year with normal summer temperatures, canes produced in greenhouses consistently out-yielded those produced in the open by about I kg per cane. Regression analyses revealed that high yields were associated with fruiting cane architecture traits such as cane height, number and length of laterals, and a low proportion of dormant buds. The single most important component was lateral length which alone accounted for 82% of the yield variation. Since lateral lengths increased from the shoot tip towards the base, cane heights in excess of 2 m are required for the attainment of top yields as the uppermost nodes with short and low-yielding laterals then can be eliminated by tipping. (C) 2009 Elsevier B.V. All rights reserved.
Abstract
Environmental control of the annual growth cycle of 'Glen Ample' raspberry has been studied in order to facilitate crop manipulation for out-of-season production. Plants propagated from root buds were raised in long days (LD) at 21 degrees C and then exposed to different temperature and daylength conditions at varying ages. Shoot growth was monitored by weekly measurements and floral initiation by regular sampling and examination of axillary bud #5. Under natural summer daylight conditions at 60 degrees N shoot growth was nearly doubled at 21 degrees C compared with 15 degrees C, while at 9 degrees C one half of the plants ceased growing and formed flower buds at midsummer. Developing shoots have a juvenile phase and could not be induced to flower before the 15-leaf stage. No significant reduction in induction requirements was found in larger plants. Plants exposed to natural light conditions from 10th August, had an immediate growth suppression at 9 and 12 degrees C with complete cessation after 4 weeks (by September 7). This coincided with the first appearance of floral primordia. At 15 degrees C both growth cessation and floral initiation occurred 2 weeks later (by September 21), while at 18 degrees C continuous growth with no floral initiation was maintained until early November when the photoperiod had fallen below 9 h. The critical photoperiod for growth cessation and floral initiation at 15 degrees C was 15 h. Plants exposed to 10-h photoperiods at 9 degrees C for 2-4 weeks had a transient growth suppression followed by resumed growth under subsequent high temperature and LD conditions, while exposure for 5 or 6 weeks resulted in complete growth cessation and dormancy induction. The critical induction period for floral initiation was 3 weeks although no transitional changes were visible in the bud before week 4. When exposed to inductive conditions for marginal periods of 3 or 4 weeks, an increasing proportion of the plants (20% and 67%, respectively), behaved as primocane flowering cultivars with recurrent growth and terminal flowering. It is concluded that growth cessation and floral initiation in raspberry are jointly controlled by low temperature and short day conditions and coincide in time as parallel outputs from the same internal induction mechanism. (C) 2008 Elsevier B.V. All rights reserved.
Abstract
A field fertilizer trial planted in late August was used to study effects of fertilizer timing and application method on flowering and ripening in strawberry cv. Korona. In treatment 1 (T1), fertilization in August prior to planting was followed by fertigation with low nutrient rate from May to August in the first harvest year. In treatment 2 (T2) all nutrients were applied as nutrient solution from May to August the first harvest year. By August in the first harvest year, the total amount of fertilizer applied was similar for both treatments (80 kg N ha(-1)). Equal amounts of water were also applied in both treatments. In the second harvest year, all the fertilizer was applied using fertigation from May to August. Both treatments were given the same fertilizer rate (80 kg N ha(-1)) to study after-effects of T1 and T2. In the first harvest year, preplant fertilized plants flowered earlier and required a higher number of days and day-degrees from anthesis to berry ripening than did T2 plants which were not fertilized until spring the first harvest year. Significant differences were found in yield but not in the number of berries, as berry size was significantly higher in T1. No significant differences were found between fertilizer treatments in the second harvest year, although T2 tended to yield the maximum number of berries later in the season than T1.
Abstract
The environmental control of flowering in five populations of Fragaria virginiana ssp. glauca and three populations of F virginiana ssp. virginiana (henceforth referred to as F virginiana), obtained as seed from the National Plant Germplasm Repository, Corvallis, OR, USA, has been studied under controlled environment conditions. Except for the F virginiana ssp. glauca population PI 551648 from the Wasatch Mountains in Utah, which was truly day-neutral across a 9 degrees - 27 degrees C temperature range, all the other populations of both sub-species behaved as quantitative (facultative) short-day (SD) plants with earlier and more abundant flowering under SD than under long-day (LD) conditions. Flowering of the remaining F virginiana ssp. glauca populations was governed by a significant interaction of photoperiod and temperature. The SD dependence for flowering increased with increasing temperature from 9 degrees C to 27 degrees C. The optimum temperature for the SD flowering response was 15 degrees - 21 degrees C. While SD promotion of flowering was more pronounced in the F virginiana populations, temperature had no significant main effect on flowering in this sub-species, demonstrating a wide temperature tolerance for flowering. Vigorous runner formation was observed in all populations, in both SD and LD, with a highly significant advancement effect of increasing temperature. The flowering and runnering responses of these E virginiana populations are discussed in relation to their putative paternity of perpetual-flowering F. X ananassa cultivars. It is concluded that, with the complex inheritance in these octoploid plants, the flowering responses of the populations studied here are not reflected in the LD flowering response of cultivated everbearing strawberries.
Abstract
The environmental control of flowering in the perpetual-flowering (everbearing) diploid strawberry Fragaria vesca ssp. semperflorens cultivars 'Rugen' and 'Baron Solemacher' has been studied in controlled environments. Seed-propagated plants were exposed to 10-h short-day (SD) and 24-h long-day (LD) conditions at temperatures ranging from 9 degrees - 27 degrees C. The results revealed a quantitative LD response of flowering that increased in strength with increasing temperature, to become almost obligatory at 27 degrees C. Occasional runner formation was observed in SD at high temperature, conditions which were inhibitory to flowering, demonstrating that runnering ability is not completely lost in these genotypes. A comparison with the perpetual-flowering octoploid F X ananassa 'Elan', in one experiment, demonstrated an identical LD X temperature interaction in the two species. The results are discussed in relation to available information on the genetics of flowering habits in the two species. Since seasonal flowering types of F vesca and E X ananassa have also been shown to share a principally identical flowering response, controlled by SD and low temperature, it is concluded that a remarkably similar flowering control system is present in the diploid F vesca and the octoploid F. X ananassa. Despite the large genetic differences between the two species, and regardless of the origin of the cultivars, the seasonal flowering types are all SD plants, while their perpetual-flowering counterparts all appear to be LD plants. In both cases, there is a pronounced interaction with temperature; the photoperiodic responses increasing with increasing temperature, in both cases. This raises the question whether a common genetic flowering control system is present in both species.
Abstract
The effect of night temperature on short day (SD) floral induction has been studied in three June-bearing strawberry cultivars of different geographic origin and compared with yield performance in the cool Nordic environment. At the optimum day temperature of 18 degrees C, the SD flowering response of the cultivars 'Florence' and 'Korona' increased significantly with increasing night temperature from 9 to 18 degrees C, while an optimum was reached at 15 degrees C in the cultivar 'Frida' that is selected under cool-environment conditions in Norway. Also, while saturated flowering response was obtained with 3 weeks of SD treatment at all temperatures in 'Frida', several plants of 'Florence' and 'Korona' failed to initiate flowers at 9 degrees C night temperature even with 5 weeks of SD. The effect of extended SD period was particularly pronounced in 'Florence'. The slow SD floral induction response of 'Florence' was associated with a 2 week delay of anthesis in subsequent long day (LD) conditions at 21 degrees C. Yield performance of the same cultivars during 2 years under field conditions at Nes Hedmark and in North Norway also demonstrated that the yield potential of 'Florence' was not realized under the climatic conditions prevailing at these locations. In both years the yields varied significantly among the cultivars,'Frida' having the highest yields followed by 'Korona', with 'Florence' far below. It is concluded that, in the Nordic environment, autumn (September) night temperatures are obviously suboptimal for yield performance of some June-bearing strawberry cultivars, and that this effect is mediated by autumn temperature effects on flower initiation responses. (C) 2008 Elsevier B.V. All rights reserved.
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Abstract
Floral induction and development requirements of a range of latitudinal and altitudinal Norwegian populations of the wild strawberry Fragaria vesca L. have been studied in controlled environments. Rooted runner plants were exposed to a range of photoperiods and temperatures for 5 weeks for floral induction and then transferred to long day (LD) at 20 degrees C for flower development. A pronounced interaction of temperature and photoperiod was shown in the control of flowering. At 9 degrees C, flowers were initiated in both short day (SD) and LD conditions, at 15 and 18 degrees C in SD only, whereas no initiation took place at 21 degrees C regardless of daylength conditions. The critical photoperiod for SD floral induction was about 16 h and 14 h at 15 and 18 degrees C, respectively, the induction being incomplete at 18 degrees C. The optimal condition for floral induction was SD at 15 degrees C. A minimum of 4 weeks of exposure to such optimal conditions was required. Although the populations varied significantly in their flowering performance, no clinal relationship was present between latitude of origin and critical photoperiod. Flower development of SD-induced plants was only marginally advanced by LD conditions, while inflorescence elongation and runnering were strongly enhanced by LD at this stage. The main shift in these responses took place at photoperiods between 16 and 17 h. Unlike all other populations studied, a high-latitude population from 70 degrees N ('Alta') had an obligatory vernalization requirement. Although flowering and fruiting in its native Subarctic environment and after overwintering in the field in south Norway, this population did not flower in the laboratory in the absence of vernalization, even with 10 or 15 weeks of exposure to SD at 9 degrees C. Flowering performance in the field likewise indicated a vernalization requirement of this high-latitude population.
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