Voici les éléments 1 - 10 sur 98
  • Publication
    Métadonnées seulement
    Manipulation of chemically mediated interactions in agricultural soils to enhance the control of crop pests and to improve crop yield
    In most agro-ecosystems the organisms that feed on plant roots have an important impact on crop yield and can impose tremendous costs to farmers. Similar to aboveground pests, they rely on a broad range of chemical cues to locate their host plant. In their turn, plants have co-evolved a large arsenal of direct and indirect defense to face these attacks. For instance, insect herbivory induces the synthesis and release of specific volatile compounds in plants. These volatiles have been shown to be highly attractive to natural enemies of the herbivores, such as parasitoids, predators, or entomopathogenic nematodes. So far few of the key compounds mediating these so-called tritrophic interactions have been identified and only few genes and biochemical pathways responsible for the production of the emitted volatiles have been elucidated and described. Roots also exude chemicals that directly impact belowground herbivores by altering their behavior or development. Many of these compounds remain unknown, but the identification of, for instance, a key compound that triggers nematode egg hatching to some plant parasitic nematodes has great potential for application in crop protection. These advances in understanding the chemical emissions and their role in ecological signaling open novel ways to manipulate plant exudates in order to enhance their natural defense properties. The potential of this approach is discussed, and we identify several gaps in our knowledge and steps that need to be taken to arrive at ecologically sound strategies for belowground pest management.
  • Publication
    Accès libre
    Belowground and aboveground herbivory differentially affect the transcriptome in roots and shoots of maize
    Plants recognize and respond to feeding by herbivorous insects by upregulating their local and systemic defenses. While defense induction by aboveground herbivores has been well studied, far less is known about local and systemic defense responses against attacks by belowground herbivores. Here, we investigated and compared the responses of the maize transcriptome to belowground and aboveground mechanical damage and infestation by two well-adapted herbivores: the soil-dwelling western corn rootworm Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae) and the leaf- chewing fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae). In responses to both herbivores, maize plants were found to alter local transcription of genes involved in phytohormone signaling, primary and secondary metabolism. Induction by real herbivore damage was considerably stronger and modified the expression of more genes than mechanical damage. Feeding by the corn rootworm had a strong impact on the shoot transcriptome, including the activation of genes involved in defense and development. By contrast, feeding by the fall armyworm induced only few transcriptional changes in the roots. In conclusion, feeding by a leaf chewer and a root feeder differentially affects the local and systemic defense of maize plants. Besides revealing clear differences in how maize plants respond to feeding by these specialized herbivores, this study reveals several novel genes that may play key roles in plant–insect interactions and thus sets the stage for in depth research into the mechanism that can be exploited for improved crop protection.
  • Publication
    Métadonnées seulement
    Plant strengtheners enhance parasitoid attraction to herbivore-damaged cotton via qualitative and quantitative changes in induced volatiles
    (2014)
    Sobhy, Islam S.
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    Background Herbivore-damaged plants release a blend of volatile organic compounds (VOCs) that differs from undamaged plants. These induced changes are known to attract the natural enemies of the herbivores and therefore are expected to be important determinants of the effectiveness of biological control in agriculture. One way of boosting this phenomenon is the application of plant strengtheners, which has been shown to enhance parasitoid attraction in maize. It is unclear if this is also the case for other important crops. Results We applied the plant strengtheners BTH (benzo (1,2,3) thiadiazole-7-carbothioic acid S-methyl ester) or laminarin to cotton plants and studied the effects on volatile releases and the attraction of three hymenopteran parasitoids, Cotesia marginiventris, Campoletis sonorensis and Microplitis rufiventris. After treated and untreated plants were induced by real or simulated caterpillar feeding, we found that BTH treatment increased the attraction of the parasitoids, whereas laminarin had no significant effect. BTH treatment selectively increased the release of two homoterpenes and reduced the emission of indole, the latter of which has been shown to interfere with parasitoid attraction in earlier studies. Canonical variate analyses of the data show that the parasitoid responses were dependent on the quality rather than the quantity of volatile emission in this tritrophic interaction. Conclusion Overall, these results strengthen the emerging paradigm that induction of plant defences with chemical elicitors such as BTH could provide a sustainable and environment-friendly strategy for biological control of pests by enhancing the attractiveness of cultivated plants to natural enemies of insect herbivores.
  • Publication
    Accès libre
    Isolation and characterization of polymorphic microsatellite loci in Acanthoscelides obvelatus Say (Coleoptera: Bruchidae)
    (2004)
    Alvarez, Nadir
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    Born, Céline
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    Risterucci, A.-M.
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    Sourrouille, P.
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    Hossaert-McKey, Martine
    Six microsatellite loci were isolated from the bruchid Acanthoscelides obtectus Say (Coleoptera: Bruchidae). Each locus was polymorphic, with the number of alleles ranging from 3 to 18. We found high levels of within-population variation at most loci, with heterozygosities ranging from 0 to 0.75. Cross-species amplification of these loci was tested in two other species of the genus Acanthoscelides, A. obvelatus Bridwell and A. argillaceus Sharp.
  • Publication
    Métadonnées seulement
  • Publication
    Métadonnées seulement
    Fatty acid phytyl ester synthesis in chloroplasts of Arabidopsis
    (2012)
    Lippold, Felix
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    vom Dorp, Katharina
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    Abraham, Marion
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    Hölzl, Georg
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    Wewer, Vera
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    Yilmaz, Jenny Lindberg
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    Lager, Ida
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    Montandon, Cyrille
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  • Publication
    Accès libre
    Bio-inoculation of yerba mate seedlings (Ilex paraguariensis St. Hill.) with native plant growth-promoting rhizobacteria: a sustainable alternative to improve crop yield
    Bergottini, Veronica M
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    Otegui, M. B
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    Sosa, D. A
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    Zapata, P. D
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    Wiss, F
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    In this study, the role of native plant growth-promoting rhizobacteria (PGPR) as bio-inoculants was assessed as an alternative to ameliorate Ilex paraguariensis St. Hill. growth in nursery comparing poorer (soil) versus richer (compost) substrates. Twelve rhizospheric strains isolated from yerba mate plantations were evaluated in vitro for their potential as PGPRs. Three isolates, identified as Kosakonia radicincitans YD4, Rhizobium pusense YP3, and Pseudomonas putida YP2, were selected on the basis of their N2 fixation activity, IAA-like compound and siderophore production, and phosphate solubilization. A highly significant positive effect of bio-inoculation with the native isolates was observed in 5-month-old seedlings cultivated in soil. The highest increase was observed in seedlings inoculated with K. radicincitans YD4 with an increase of 183 % in the dry shoot weight and a 30 % increase in shoot N content. In contrast, in compost, no increment in the dry weight was observed; however, an increase in content in some macronutrients in shoots was observed. Remarkably, when plant biomass was compared between soil and compost, seedlings inoculated with K. radicincitans YD4 in soil produced the highest yields, even though higher yields could be expected in compost due to the richness of this substrate. In conclusion, bio-inoculation of yerba mate seedlings with native PGPR increases the yield of this crop in nursery and could represent a promising sustainable strategy to improve yerba mate growth in low-fertility soils.