Browsing by Subject "flowering"

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  • Qin, Kaiyue Jr (Helsingin yliopisto, 2020)
    Strawberries (Fragaria sp.) are perennial plants that belong to Rosaceae family. According to flowering habit, strawberries are classified as seasonal flowering and perpetual flowering strawberries. Environmental factors regulate flowering in plants. Among them, photoperiod and temperature are two important cues to affect flowering in strawberries. Besides, FT is a general flowering activator in many plant species. This thesis explored the flowering habits and FT expression level of two diploid strawberries F. bucharica and F. nilgerrensis under short and long day at cool temperature at 11 °C. The results were compared with F. vesca which has been studied earlier. After 2, 4 and 6 weeks of cool temperature (11 °C) treatment, all F. vesca and the majority of F. bucharica flowered regardless of photoperiod. As for F. nilgerrensis, there was no floral induction under SD and 20 % flowering rate after 6 weeks of LD treatment. After 4 weeks of the treatment, the expression of FT was down-regulated in F. vesca and F. bucharica compared with control groups under long day at 20 °C. In conclusion, the cool temperature at 11 °C induced flowering both in F. vesca and F. bucharica. The photoperiod affected flowering in F. vesca, while not in F. bucharica. As for F. nilgerrensis, the treatments were not strongly inductive for flowering. It may need more time for floral induction. The FT1 expression was down regulated after 4-week cool temperature treatments in F. vesca and F. bucharica, which was negatively correlated with flower induction. The photoperiod and temperature significantly affect branch crown formation in F. nilgerrensis, while the temperature had significant effects on runner formation and leaf formation in these three species.
  • Luomajoki, Alpo (The Society of Forestry in Finland - The Finnish Forest Research Institute, 1999)
    Male flowering was studied at the canopy level in 10 silver birch (Betula pendula Roth) stands from 8 localities and in 14 downy birch (B. pubescens Ehrh.) stands from 10 localities in Finland from 1963 to 1973. Distributions of cumulative pollen catches were compared to the normal Gaussian distribution. The basis for the timing of flowering was the 50 per cent point of the anthesis-fitted normal distribution. To eliminate effects of background pollen, only the central, normally distributed part of the cumulative distribution was used. Development up to the median point of the distribution was measured and tested in calendar days, in degree days (> 5 °C) and in period units. The count of each parameter began on and included March 19. Male flowering in silver birch occurred from late April to late June depending on latitude, and flowering in downy birch took place from early May to early July. The heat sums needed for male flowering varied in downy birch stands latitudinally but there was practically no latitudinal variation in heat sums needed for silver birch flowering. The amount of male flowering in stands of both birch species were found to have a large annual variation but without any clear periodicity. The between years pollen catch variation in stands of either birch species did not show any significant latitudinal correlation in contrast to Norway spruce stands. The period unit heat sum gave the most accurate forecast of the timing of flowering for 60 per cent of the silver birch stands and for 78.6 per cent of the for downy birch stands. Calendar days, however, gave the best forecast for silver birch in 25 per cent of the cases, while degree days gave the best forecast for downy birch in 21.4 per cent of the cases. Silver birch seems to have a local inclination for a more fixed flowering date compared to downy birch, which could mean a considerable photoperiodic influence on flowering time of silver birch. Silver birch and downy birch had different geographical correlations. Frequent hybridization of birch species occurs more often in northern Finland in than in more southern latitudes. The different timing in flowering caused increasing scatter in flowering times in the north, especially in the case of downy birch. The chance of simultaneous flowering of silver birch and downy birch so increased northwards due to a more variable climate and also higher altitudinal variations. Compared with conifers, the reproduction cycles of both birch species were found to be well protected from damage by frost.
  • Luukkanen, Olavi (Suomen metsätieteellinen seura, 1981)
  • Luukkanen, Olavi; Johansson, Stig (Suomen metsätieteellinen seura, 1980)
  • Andrés Jiménez, Javier (Helsingfors universitet, 2017)
    The Rosaceae family accounts for more than 90% of the total fresh fruit production in Finland and for more than 25% worldwide in 2013. Thus, improving the yield potential of Rosaceae species works in favor of economic growth and food security. To achieve that, expanding the knowledge on Rosaceae species is required. Fragaria vesca (F. vesca), particularly the everbearing F. vesca semperflorens accession ‘Hawaii-4’ (H4), provides several features that makes it formidable as a model organism for the study of physiological processes in Rosaceae species, where the CENTRORADIALIS/TERMINALFLOWER 1/SELF-PRUNING (CETS) genes play a remarkable role. In this Thesis, I have studied the expression patterns and functions of the CETS genes by performing gene expression analysis, generation of H4 transgenic lines and observation on H4 plants (both transgenic and wild type) grown under different sets of conditions. My results confirmed the expression patterns and functions previously reported for F.vesca TERMINAL FLOWER1 and F.vesca FLOWERING LOCUS T1. I showed that F.vesca CENTRORADIALIS-LIKE2 is a floral repressor and demonstrated that F.vesca FLOWERING LOCUS T3 is a flowering promoter. Additionally, our data suggest that F.vesca MOTHER OF FT is directly related with stolon formation and that F.vesca CENTRORADIALIS-LIKE1 is most likely a floral repressor. This new information could be used in the future to improve the efficiency of Rosaceae crops farming by adapting flowering and vegetative responses and also for breeding more productive Rosaceae crops.
  • Koskela, Elli (Helsingfors universitet, 2009)
    Strawberry (Fragaria × ananassa) is the most important berry crop cultivated in Finland. Due to the species' economic importance, there is a national breeding programme aimed at extending the cropping season from the current one month to up to three months. This could be achieved by growing cultivars which would initiate flowers throughout the summer months, without the requirement of a period of short days as is the case with currently grown cultivars. The cultivated strawberry is an octoploid and therefore has complex patterns of inheritance. It is desirable to study the genetic mechanisms of flowering in the closely related but diploid species F. vesca (L). In the diploid Fragaria, a mutation in a single locus, namely the SEASONAL FLOWERING LOCUS (Sfl), changes the flowering phenotype from seasonal to perpetual flowering. There is also an array of genetic tools available for F. vesca, which facilitate genetic studies at molecular level. Experiments described here aimed at elucidating the identity of the gene which confers perpetual flowering in F. vesca by exploring the flowering characteristics and genotypes of five F2 populations (crosses between seasonal × perpetual flowering cultivars). The study took advantage of a genetic map for diploid Fragaria, publicly available EST and genomic Fragaria sequences and a recently developed BAC library. Sequence information was used for designing gene–specific primers for a host of flowering–related candidate genes, which were subsequently mapped on the diploid Fragaria genetic map. BAC library was screened with molecular markers supposedly located close to the Sfl, with the aim of positionally cloning the Sfl. Segregation of flowering phenotypes in the five F2 populations showed, that the Sfl indeed controls flowering in all the tested cultivars. A genetic map was constructed of the chromosome with the Sfl, and a positional cloning attempt was initiated with the closest flanking markers. 45 gene–specific primers pairs were designed for 21 flowering–related genes, and eight genes were successfully mapped on the diploid Fragaria map. One of the mapped genes, namely PRR7, located very close to the Sfl, and is a potential candidate for the gene that has evaded identification so far.
  • Jokela, Venla; Trevaskis, Ben; Seppanen, Mervi M. (2015)
    Timothy is a perennial forage grass grown commonly in Boreal regions. This study explored the effect of vernalization and photoperiod (PP) on flowering and growth characteristics and how this related to changes in expression of three flowering related genes in accessions from different geographic origin. Large variation was found in accessions in their vernalization and PP responses. In southern accessions vernalization response or requirement was not observed, the heading date remained unchanged, and plants flowered without vernalization. On the contrary, northern types had obligatory requirement for vernalization and long PP, but the tiller elongation did not require vernalization at 16-h PP. Longer vernalization or PP treatments reduced the genotypical differences in flowering. Moreover, the vernalization saturation progressed stepwise from main tiller to lateral tillers, and this process was more synchronized in southern accessions. The expression of PpVRN1 was associated with vernalization while PpVRN3 accumulated at long PP. A crucial role for PpVRN3 in the transition to flowering was supported as in southern accession the transcript accumulated in non-vernalized plants after transfer to 16-h PP, and the apices transformed to generative stage. Differences in vernalization requirements were associated with variation in expression levels of PpVRN1 and PpVRN3, with higher expression levels in southern type. Most divergent transcript accumulation of PpMADS10 was found under different vernalization conditions. These differences between accessions can be translated into agronomic traits, such as the tiller composition of canopy, which affects the forage yield. The southern types, with minimal vernalization response, have fast re-growth ability and rapidly decreasing nutritive value, whereas northern types grow slowly and have better quality. This information can be utilized in breeding for new cultivars for longer growing seasons at high latitudes.
  • Rantanen, Marja; Kurokura, Takeshi; Mouhu, Katriina; Pinho, Paulo; Tetri, Eino; Halonen, Liisa; Palonen, Pauliina; Elomaa, Paula; Hytonen, Timo (2014)
  • Richterich, Daniel (Helsingin yliopisto, 2014)
    The strawberry is the most widely cultivated berry in Finland. Producers in Finland grow short-day varieties of strawberry with the mid-season variety Polka being the most popular. Very little breeding is done in Finland and the characteristics of foreign varieties are not tailored to the local growing con-ditions here. Given these circumstances, it is a challenge to choose varieties for production that will flourish in Finland. The calculated and polyvalent use of different strawberry varieties could prolong the growing season and help stimulate productivity and growth in this area of horticulture. The aim of this research is to develop a rapid test for identifying strawberry varieties whose flowering phenology will suit production in Finland. In this research we aimed to develop a test based on short-day treatment to compare the earliness of different varieties. The influence of short-day treatment on flowering and growth was studied in seven short-day strawberry varieties in a greenhouse experiment. Beside the influence of the treatment on the timing of flowering we tested the relationship between earliness and changes in the vegetative growth of our varieties. The experimental conditions comprised two day-length treatments and one control. The first short-day-treatment lasted six weeks with a photoperiod of 12 h. The second short-day treatment, a so called “step” treatment, lasted nine weeks. The day-length in the step treatment was shortened every three weeks, starting at 16 h, and then dropping to 14 h and 12 h. In the long-day control the day-length was 18 h. The greenhouse temperature was a constant 18 ºC in all treatments. We tested early varieties Honeoye, Elianny, Flair and Wendy, the mid-season variety Polka and late varieties Bounty and Florence. The plants in our experiment didn’t develop as we expected. The early variety Wendy was amongst the first to flower, and the late variety Florence amongst the last in both treatments. The earliness of the other varieties we tested was not consistent with how these varieties flower in the open field. Furthermore, the relative vegetative growth couldn’t be associated with the flowering time. In both short-day treatments the growth of the runners stopped first in the early varieties Wendy, Honeoye and Flair. In the remaining varieties, the growth of the runners was unrelated to the expected earliness of the flowering. The length of the petiole was responsive to the first short-day treatment, but growth of the runners and the petioles did not correlate with early flowering. However slow growth of the late variety, Florence, suggests that the growth rate may be connected with the flower phenology in the variety. Finally, Polka was the variety to exhibit most crown branching in this experiment. According to the results of this experiment the earliness of short-day strawberry varieties cannot be determined with just an experimental short-day treatment. The other growing conditions in the green-house are also likely to affect the response of the tested varieties, potentially masking or interacting with the day-length effect. In addition to day-length, the response of the varieties to the temperature, and to the combined effect of day-length and temperature, should be taken into account. A suitable greenhouse test could comprise day-length and temperature treatments or the combination of both of them. Alternatively flower induction could be performed in the field and subsequently plants could be forced in the greenhouse.
  • Fan, Guangxun; Andres, Javier; Olbricht, Klaus; Koskela, Elli; Hytönen, Timo (2022)
    In perennial fruit and berry crops of the Rosaceae family, flower initiation occurs in late summer or autumn after downregulation of a strong repressor TERMINAL FLOWER1 (TFL1), and flowering and fruiting takes place the following growing season. Rosaceous fruit trees typically form two types of axillary shoots, short flower-bearing shoots called spurs and long shoots that are, respectively, analogous to branch crowns and stolons in strawberry. However, regulation of flowering and shoot architecture differs between species, and environmental and endogenous controlling mechanisms have just started to emerge. In woodland strawberry (Fragaria vesca L.), long days maintain vegetative meristems and promote stolon formation by activating TFL1 and GIBBERELLIN 20-OXIDASE4 (GA20ox4), respectively, while silencing of these factors by short days and cool temperatures induces flowering and branch crown formation. We characterized flowering responses of 14 accessions of seven diploid Fragaria species native to diverse habitats in the northern hemisphere and selected two species with contrasting environmental responses, Fragaria bucharica Losinsk. and Fragaria nilgerrensis Schlecht. ex J. Gay for detailed studies together with Fragaria vesca. Similar to F. vesca, short days at 18 degrees C promoted flowering in F. bucharica, and the species was induced to flower regardless of photoperiod at 11 degrees C after silencing of TFL1. F. nilgerrensis maintained higher TFL1 expression level and likely required cooler temperatures or longer exposure to inductive treatments to flower. We also found that high expression of GA20ox4 was associated with stolon formation in all three species, and its downregulation by short days and cool temperature coincided with branch crown formation in F. vesca and F. nilgerrensis, although the latter did not flower. F. bucharica, in contrast, rarely formed branch crowns, regardless of flowering or GA20ox4 expression level. Our findings highlighted diploid Fragaria species as rich sources of genetic variation controlling flowering and plant architecture, with potential applications in breeding of Rosaceous crops.
  • Koski, Veikko (Suomen metsätieteellinen seura, 1980)
  • Siljamo, Pilvi; Sofiev, Mikhail; Ranta, Hanna; Linkosalo, Tapio; Kubin, Eero; Ahas, Rein; Genikhovich, Eugene; Jatczak, Katarzyna; Jato, Victoria; Nekovar, Jiri; Minin, Alexander; Severova, Elena; Shalaboda, Valentina (2008)
  • Koskela, Elli Aurora; Sonsteby, Anita; Flachowsky, Henryk; Heide, Ola Mikal; Hanke, Magda-Viola; Elomaa, Paula; Hytönen, Timo (2016)
    The effects of daylength and temperature on flowering of the cultivated octoploid strawberry (Fragaria x 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.
  • Mäkelä, Tii (Helsingfors universitet, 2013)
    The aim of this research was to find out the effect of photoperiod and quantity of light on growth and flowering of arctic bramble (Rubus arcticus L.) cv. Mesma. The object was also to find out the effect of light on development of floral organs in apical buds of root suckers. Three 12 week long standard treatments were: LD (long day, 12 h HPS-light + 12 h incandescent light), SD (short day, 12 h HPS-light) and HPS (24 h HPS-light). Additionally, the effect of changing the light conditions was examined in four treatments: SD->LD (6 wk SD-treatment + 6 wk LD-treatment), SD->HPS (6 wk SD-treatment + 6 wk HPS-treatment), HPS->SD (6 wk HPS-treatment + 6 wk SD-treatment) and HPS->LD (6 wk HPS-treatment + 6 wk LD-treatment). In standard treatments the vegetative growth determined as the dry weight of the shoots was increased in HPS and decreased in SD. Elongation of shoot was enhanced by LD and development of new leaves was increased in LD and HPS. The number of flowers was highest in HPS and lowest in SD. The average dry weight of a flower and the number of flowers in relation to vegetative growth were increased in HPS. In SD growth and flowering were suppressed towards the end of the experiment. When plants were moved from SD to HPS or LD, growth and flowering were continued. Growth and flowering were clearly enhanced by continuous HPS light. Cessation of growth and flowering in SD suggests that the plants were becoming dormant. Growth and flowering continued when plants were moved from SD to LD or HPS, which indicates that plants were not fully dormant. The differences between treatments LD and SD were probably a consequence of dormancy induction in SD. Floral initiation in apical buds of root suckers occurred in all three standard treatments regardless of photoperiod or quantity of light.