522 research outputs found
Etude de la transmission de Xanthomonas campestris pv. campestris aux graines d'Arabidopsis thaliana
Ecological patterns of seed microbiome diversity, transmission, and assembly
Seeds are involved in the transmission of microorganisms from one plant generation to another and consequently act as the initial inoculum for the plant microbiota. The purpose of this mini-review is to provide an overview of current knowledge on the diversity, structure and role of the seed microbiota. The relative importance of the mode of transmission (vertical vs horizontal) of the microbial entities composing the seed microbiota as well as the potential connections existing between seed and other plant habitats such as the anthosphere and the spermosphere is discussed. Finally the governing processes (niche vs neutral) involved in the assembly and the dynamics of the seed microbiota are examined
PHENOPLANT, a feature of PHENOTIC : Phenotyping horticultural products and the interactions between host plants and pathogens
Non-perturbative Power Corrections to Ghost and Gluon Propagators
We study the dominant non-perturbative power corrections to the ghost and
gluon propagators in Landau gauge pure Yang-Mills theory using OPE and lattice
simulations. The leading order Wilson coefficients are proven to be the same
for both propagators. The ratio of the ghost and gluon propagators is thus free
from this dominant power correction. Indeed, a purely perturbative fit of this
ratio gives smaller value (MeV) of \Lambda_{\ms} than the one
obtained from the propagators separately(MeV). This argues in
favour of significant non-perturbative power corrections in the
ghost and gluon propagators. We check the self-consistency of the method.Comment: 14 pages, 4 figures; replaced with revised version, to appear in JHE
Niches and routes of transmission of Xanthomonas citri pv. fuscans to bean seeds
Aims
Seeds are vectors of a diversified microbiota including plant pathogens. To better understand transmission of common bacterial blight (CBB) agents to bean seeds, we analyzed the role of non-pathogenic xanthomonads on seed transmission efficiency and investigated the location of Xanthomonas citri pv. fuscans (Xcf) into seeds and plantlets.
Methods
Competition between CBB and NP strains was initially assessed in vitro and then extended in planta to monitor the impact of co-inoculation on Xcf seed transmission. Moreover, location of Xcf strains in seeds and seedlings was visualized using a combination of gfp-tagged strain and DOPE-FISH/CSLM.
Results
Whereas CBB agent growth was inhibited in vitro by some seed-borne non-pathogenic xanthomonads strains, these strains did not transmit efficiently to seed through floral pathway and did not affect Xcf seed transmission. Xcf cells were observed entering seed through vascular elements and parenchyma of funiculus, but also micropyle and testa. Xcf cells were observed, moreover, among other bacteria on radicle surfaces, especially tip, in cotyledons, and plumules.
Conclusions
CBB agents are more efficient than non-pathogenic xanthomonads in using the floral route to colonize seeds. CBB agents are located within different niches in the seed tissues up to the embryonic axis
Etude du mode de colonisation des graines et des siliques de la plante modÚle Arabidospis thaliana par Alternaria brassicicola, champignon pathogÚne des plantes de la famille des Brassicacées
Aggressive Emerging Pathovars of Xanthomonas arboricola Represent Widespread Epidemic Clones Distinct from Poorly Pathogenic Strains, as Revealed by Multilocus Sequence Typing
Deep and comprehensive knowledge of the genetic structure of pathogenic species is the cornerstone on which the design of precise molecular diagnostic tools is built. Xanthomonas arboricola is divided into pathovars, some of which are classified as quarantine organisms in many countries and are responsible for diseases on nut and stone fruit trees that have emerged worldwide. Recent taxonomic studies of the genus Xanthomonas showed that strains isolated from other hosts should be classified in X. arboricola, extending the host range of the species. To investigate the genetic structure of X. arboricola and the genetic relationships between highly pathogenic strains and strains apparently not relevant to plant health, we conducted multilocus sequence analyses on a collection of strains representative of the known diversity of the species. Most of the pathovars were clustered in separate monophyletic groups. The pathovars pruni, corylina, and juglandis, responsible for pandemics in specific hosts, were highly phylogenetically related and clustered in three distinct clonal complexes. In contrast, strains with no or uncertain pathogenicity were represented by numerous unrelated singletons scattered in the phylogenic tree. Depending on the pathovar, intra- and interspecies recombination played contrasting roles in generating nucleotide polymorphism. This work provides a population genetics framework for molecular epidemiological surveys of emerging plant pathogens within X. arboricola. Based on our results, we propose to reclassify three former pathovars of Xanthomonas campestris as X. arboricola pv. arracaciae comb. nov., X. arboricola pv. guizotiae comb. nov., and X. arboricola pv. zantedeschiae comb. nov. An emended description of X. arboricola Vauterin et al. 1995 is provided
Assembly of seed-associated microbial communities within and across successive plant generations
Background and aims
Seeds are involved in the transmission of microorganisms from one plant generation to another and consequently may act as the initial inoculum source for the plant microbiota. In this work, we assessed the structure and composition of the seed microbiota of radish (Raphanus sativus) across three successive plant generations.
Methods
Structure of seed microbial communities were estimated on individual plants through amplification and sequencing of genes that are markers of taxonomic diversity for bacteria (gyrB) and fungi (ITS1). The relative contribution of dispersal and ecological drift in inter-individual fluctuations were estimated with a neutral community model.
Results
Seed microbial communities of radish display a low heritability across plant generations. Fluctuations in microbial community profiles were related to changes in community membership and composition across plant generations, but also to variation between individual plants. Ecological drift was an important driver of the structure of seed bacterial communities, while dispersal was involved in the assembly of the fungal fraction of the seed microbiota.
Conclusions
These results provide a first glimpse of the governing processes driving the assembly of the seed microbiota
Isobutyl acetate: electronic state spectroscopy by high-resolution vacuum ultraviolet photoabsorption, He(I) photoelectron spectroscopy and ab initio calculations
The high-resolution vacuum ultraviolet photoabsorption spectrum of isobutyl acetate, C6H12O2, is presented here and was measured over the energy range 4.3â10.8 eV (290â115 nm). Valence and Rydberg transitions with their associated vibronic series have been observed in the photoabsorption spectrum and are assigned in accordance with new ab initio calculations of the vertical excitation energies and oscillator strengths. The measured photoabsorption cross sections have been used to calculate the photolysis lifetime of this ester in the Earthâs upper atmosphere (20â50 km). Calculations have also been carried out to determine the ionization energies and fine structure of the lowest ionic state of isobutyl acetate and are compared with a photoelectron spectrum (from 9.5 to 16.7 eV), recorded for the first time. Vibrational structure is observed in the first photoelectron band of this molecule
Imagerie thermique pour les sciences du végétal : applications à la détection précoce de pathogÚnes à la surface des feuilles
- âŠ