Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2012
Forfattere
DJ Sargent T Passey N Surbanovski E. Lopez Girona P Kuchta Jahn Davik R. Harrison A Passey AB Whitehouse DW SimpsonSammendrag
Det er ikke registrert sammendrag
Forfattere
Jens Rohloff Muath Alsheikh Gage Koehler Robert Charles Wilson Jahn Davik Stephen K, RandallSammendrag
Det er ikke registrert sammendrag
Sammendrag
The winter hardiness of strawberry cultivars used in perennial production systems varies greatly, although a strong linkage exists between transcriptional and metabolic changes during cold acclimation. Still, little information is available on how plant metabolism adapts to cold and freezing temperatures under natural temperature and light conditions. In order to examine the hardening process of overwintering meristematic tissue in Fragaria x ananassa, crown samples of field-grown cvs. ‘Polka’ and ‘Honeoye’ were consecutively collected over a period of 15 weeks, i.e. from the end of the season (week 35/ end August) until midwinter (week 50/ December). Samples were subjected to qGC MS metabolite profiling to assess the reconfiguration of central metabolism, and characterize the regulation of selected compatible solutes (amino acids, Krebs metabolites, sugars, polyols). Besides changes in amino acid patterns (glutamic acid, aspartic acid, and asparagine), monosaccharide levels (fructose) were strongly enhanced until the end of the acclimation period in cv. ‘Honeoye’ (180-fold compared to start control). In contrast, ‘Polka’ showed a concentration peak (36-fold) in week 47 and a decline towards week 50. Also sucrose levels were steadily enhanced throughout the cold hardening period with averagely 6-fold higher levels in ‘Honeoye’ compared to ‘Polka’, thus underscoring cultivar differences. However, both cultivars showed a clear decline in sucrose levels after week 47. Particularly, the raffinose pathway was affected leading to strongly and transiently increased levels of the precursor galactinol (week 42/ mid October) and the trisaccharide raffinose (weeks 43 to 47/ end October to mid November). While galactinol biosynthesis was obviously earlier induced in cv. ‘Polka’ (week 38) compared to ‘Honeoye’ (week 39), subsequent raffinose production and concentration peaks were clearly delayed in ‘Polka’ (week 47) in contrast to ‘Honeoye’ (week 45). Major metabolic changes in both cultivars coincided with a decrease in daylength below 14 h after week 37 (mid September), and a consistent drop below 10°C average day temperature in week 39 (end September). The effect of temperature and light conditions on metabolic cold acclimation in field-grown strawberry is discussed. Keywords: Winter hardiness, metabolite profiling, quadrupole gas chromatography-mass spectrometry (qGC-MS), temperature, light
Forfattere
Jens Rohloff Joachim Kopka Alexander Erban Per Winge Robert Charles Wilson Atle M. Bones Jahn Davik Stephen K, Randall Muath AlsheikhSammendrag
Winter freezing damage is a crucial factor in overwintering crops such as the octoploid strawberry (Fragaria × ananassa Duch.) when grown in a perennial cultivation system. Our study aimed at assessing metabolic processes and regulatory mechanisms in the close-related diploid model woodland strawberry (Fragaria vesca L.) during a 10-days cold acclimation experiment. Based on gas chromatography/ time-of-flight-mass spectrometry (GC/TOF-MS) metabolite profiling of three F. vesca genotypes, clear distinctions could be made between leaves and non-photosynthesizing roots, underscoring the evolvement of organ-dependent cold acclimation strategies. Carbohydrate and amino acid metabolism, photosynthetic acclimation, and antioxidant and detoxification systems (ascorbate pathway) were strongly affected. Metabolic changes in F. vesca included the strong modulation of central metabolism, and induction of osmotically-active sugars (fructose, glucose), amino acids (aspartatic acid), and amines (putrescine). In contrast, a distinct impact on the amino acid proline, known to be cold-induced in other plant systems, was conspicuously absent. Levels of galactinol and raffinose, key metabolites of the cold-inducible raffinose pathway, were drastically enhanced in both leaves and roots throughout the cold acclimation period of 10 days. Furthermore, initial freezing tests and multifaceted GC/TOF-MS data processing (Venn diagrams, Independent Component Analysis, Hierarchical Clustering) showed that changes in metabolite pools of cold-acclimated F. vesca were clearly influenced by genotype.
Forfattere
Jens Rohloff Pankaj Barah Per Winge Jahn Davik Robert Wilson Stephen K, Randall Atle M. Bones Muath Alsheikh-YousefSammendrag
Freezing damage is a crucial factor in the cultivation of perennial crops. Overwintering plants acclimate to decreasing temperatures in their environment and thus, prevent freezing damage of plant tissue. To assess transcriptional and metabolic changes in meristematic tissue (crowns) of octoploid strawberry (Fragaria × ananassa Duch.), acclimation experiments were carried out at above-zero temperature (2 °C) using three cultivars with contrasting cold tolerance: ‘Elsanta’ < ‘Frida’ < ‘Jonsok’. Crowns were sampled after 1 day (d), 2d, 2 weeks (w) and 6w in order to detect short- and long-term metabolic shifts. GC/MS-based metabolite profiling revealed more than 140 metabolites (identified structures, not-annotated mass spectral tags, and unidentified metabolites). Transcriptional changes were assessed at two time points (2d and 6w) using a customized Fragaria microarray chip developed as a joint collaboration between Graminor Breeding Ltd. and NTNU. A total of 4061 differentially regulated transcripts (unique 60-mer probes) with a p-value≤0.05 were detected in all hybridizations. Microarray analysis revealed the up-regulation of ~100 cold-responsive transcripts (TFs and dehydrins), also including enzymes involved in starch breakdown and raffinose biosynthesis. Gene-metabolite correlation analysis revealed strong connectivity in components of Krebs-cycle (citric and succinic acid), amino acids (isoleucine, aspartic acid, glutamic acid, valine and phenylalanine) and the raffinose pathway. Metabolite levels of hexoses (fructose and glucose), trisaccharides (raffinose), amino acids (aspartic acid, alanine and serine), phenols (gallic acid) and several polyphenols still increased during long-term acclimation phase. Varietal differences could be clearly explained by Venn diagrams: frost-tolerant ‘Jonsok’ showed least individual up- or down-regulated transcripts (2 d), and least commonly shared transcripts with frost-sensitive ‘Elsanta’ (2d and 6w). Further multivariate statistics and network analyses underscored genotype-dependent cold responses, and might further guide in the identification of frost-tolerant vs. sensitive plants in diverse Fragaria accessions or cross-breeding populations .
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Abdelhameed Elameen DenisTourvieille de Labrouhe Emmanuelle Mestries Sonja Klemsdal Sophia Ahmed François DelmotteSammendrag
Plasmopara halstedii is a diploid oomycete plant pathogen causing downy mildew on sunflower (Helianthus annuus). Due to changes in cultural systems and the introduction of new exotic cultivars, the pathogen developed many races and have now become a serious problem affecting sunflower growing fields in Europe. The yield losses in sunflower crop caused by P. halstedii can be up to 85 %.
Forfattere
Abdelhameed ElameenSammendrag
Background to the research and aims. Sunflower downy mildew exhibit mixed asexual and sexual reproduction. Rare events of recombination can have a drastic effect on the reshuffling of genetic material and result in the emergence of new virulence combinations. Overview of the methods. In this study, we have used a molecular epidemiology approach to identify population sources, investigate the mating system and track pathogen movement at the field scale. Using a hierarchical sampling design, we have collected 250 P. halstedii isolates from 20 geo-referenced sites in an infected sunflower field located in Southern France. These samples were genetically characterized using 12 single nucleotide polymorphisms markers (SNP) and one microsatellite locus(Giresse et al. 2007) and, for a subset of 60 samples, the virulence profile was determined. Key results. Characterization of virulence profiles revealed the presence of 8 races within the field (100, 300, 304, 307, 703, 704, 707, 714), race 304 being predominant among the samples tested. Race were randomly distributed within the field. Among the 250 isolates that were genotyped, there were 109 different multilocus genotypes (MLG), of which four were highly represented. The significant deficit in heterozygotes observed confirmed that P. halstedii is a highly selfing species (Delmotte et al. 2008). Bayesian clustering analyses revealed that isolates belonged to two genetically differentiated groups (FST> 0.2) that were correlated with race. A low level of genetic differentiation (FST = 0.06) was observed among the 20 sites that were constituted of a mixture of samples from the two groups. Theestimation of gene flow using hierarchical FST and spatial autocorrelation analysis bring evidence a lack of spatial genetic structure that likely result from field plowing. Finally, the estimation of gene flow atvarious scales using hierarchical FST and spatial autocorrelation analysis bring evidence for race emergence through genetic recombination between differentiated genetic genotypes. Main conclusions. This study brings evidence for an absence of spatial genetic structure of P. halstedii population, that could result from field plowing. It also reveals that genetically and phenotypically (virulence) differentiated isolates of P. hasltedii do coexist at a very fine spatial scale. The coexistence of genetically and phenotypically differentiated isolates of P. hasltedii may allow the emergence of new races through recombination. Nature of the contribution to current knowledge. This study has allowed to identify and delineate pathogen populations at the field scale. By bringing new insights in to the evolutionary mechanisms responsible for the emergence of races, these results will help identifying management units for sunflower protection strategies. Keywords. Plasmopara halstedii, race, pathotype, virulence evolution, population genetics
Forfattere
Abdelhameed Elameen DenisTourvieille de Labrouhe Emmanuelle Mestries Sonja Klemsdal Sophia AhmedSammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag