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Uppsala, Sweden

Christensen B.,AgroTech A S | Sriskandarajah S.,Uppsala BioCenter | Jensen E.B.,Copenhagen University | Lutken H.,Copenhagen University | Muller R.,Copenhagen University
Acta Horticulturae | Year: 2010

In Kalanchoë blossfeldiana, root inducing lines were regenerated from hairy roots produced by transformation with the natural occurring bacteria A. rhizogenes. Transformed plants (T1) displayed distinct changes in plant morphology. A number of T1-lines were analysed thoroughly in greenhouse trials. Several lines had a more compact growth habit and an increased number of lateral shoots. Time to flowering was delayed in most lines. However, for one line the flowering period was similar to the control plants. In ethylene free environment, transformants performed better than control plants and single flowers lasted longer. In response to exogenous ethylene, flowers of T1-lines exhibited increased tolerance compared to control plants. Possible mechanisms behind the improved postharvest performance of plants transformed with rol genes are presently investigated. Crossings between T 1-lines and the cultivar 'Sarah' proved the heredity of the traits of interest, since dwarfism was also observed in the offspring. The presence of rol genes was proved in those F1 progenies exhibiting dwarfism. The heredity of the traits will be further investigated. Selecting for a compact growing plant, without delayed flowering and improved postharvest performance will be of great value for further breeding programmes. Source


Bakys R.,Uppsala BioCenter | Vasaitis R.,Uppsala BioCenter | Skovsgaard J.P.,Swedish University of Agricultural Sciences
Plant Protection Science | Year: 2013

The extent and temporal pattern of crown damage (attributed to Hymenoscyphus pseudoalbidus) in even-aged stands of Fraxinus excelsior in relation to bud flushing phenotype, stand density, and season was investigated. Data were collected in 2007 in four statistically designed thinning experiments located in 12-15-years old plantations of ash in Denmark. The study included 21 plots of four contrasting, residual stand densities: (1) 1700-5500 trees/ha (unthinned control plots), (2) 1500 trees/ha, (3) 500 trees/ha, and (4) 100-150 trees/ha. Assessments included estimation of flushing phenotype in May, followed by evaluation of severity of crown damage (percentage of crown killed) in June and September. Simultaneously, for each tree, the presence or absence of crown wilt and dead tops were recorded. The seasonal pattern of disease severity (average crown damage) was similar in all stands, and disregarding stand density the extent of tree crown damage increased significantly towards the end of the growing season (P < 0.005). Disease severity was the worst in unthinned plots, but otherwise unrelated to stand density. Late-flushing trees were most severely affected (P < 0.001). The observed patterns of disease severity are probably associated with ecological features of the pathogen that still remain largely unknown. Source


Nalawade S.,Uppsala BioCenter | Nalawade S.,Mahyco Research Center | Liu C.,Hunan Agricultural University | Jansson C.,Lawrence Berkeley National Laboratory | Sun C.,Uppsala BioCenter
Applied Energy | Year: 2012

We have developed a protocol for rapid generation of barley plants with introduced genes by employing techniques of tissue culture, plant regeneration and crossing. Compared to conventional protocols, the time between pollination of T0 plants and identification of phenotypic expression in the T1 generation is reduced from around 17-9weeks. All of the selected candidates after the tissue culture screening exhibited phenotypic expression. Furthermore, by utilizing ordinary pollen crossing, we demonstrated a route for introduction of genes to a recalcitrant barley elite cultivar. This Tissue Culture after Crossing (TCC) procedure significantly enhances the prospects for producing transgenic barley lines from desirable germplasm. We suggest that the TCC method will contribute to improve barley as a promising bioenergy crop. © 2011 Elsevier Ltd. Source


Beste L.,Uppsala BioCenter | Beste L.,University of Stockholm | Nahar N.,Uppsala BioCenter | Dalman K.,Swedish University of Agricultural Sciences | And 4 more authors.
Plant Physiology | Year: 2011

To explore mechanisms in plant sterol homeostasis, we have here increased the turnover of sterols in Arabidopsis (Arabidopsis thaliana) and potato (Solanum tuberosum) plants by overexpressing four mouse cDNA encoding cholesterol hydroxylases (CHs), hydroxylating cholesterol at the C-7, C-24, C-25, or C-27 positions. Compared to the wild type, the four types of Arabidopsis transformant showed varying degrees of phenotypic alteration, the strongest one being in CH25 lines, which were darkgreen dwarfs resembling brassinosteroid-related mutants. Gas chromatography-mass spectrometry analysis of extracts from wild-type Arabidopsis plants revealed trace levels of α and βforms of 7-hydroxycholesterol, 7-hydroxycampesterol, and 7-hydroxysitosterol. The expected hydroxycholesterol metabolites in CH7-, CH24-, and CH25 transformants were identified and quantified using gas chromatography-mass spectrometry. Additional hydroxysterol forms were also observed, particularly in CH25 plants. In CH24 and CH25 lines, but not in CH7 ones, the presence of hydroxysterols was correlated with a considerable alteration of the sterol profile and an increased sterol methyltransferase activity in microsomes. Moreover, CH25 lines contained clearly reduced levels of brassinosteroids, and displayed an enhanced drought tolerance. Equivalent transformations of potato plants with the CH25 construct increased hydroxysterol levels, but without the concomitant alteration of growth and sterol profiles observed in Arabidopsis. The results suggest that an increased hydroxylation of cholesterol and/or other sterols in Arabidopsis triggers compensatory processes, acting to maintain sterols at adequate levels. © 2011 American Society of Plant Biologists. All Rights Reserved. Source

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