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Found 817 results.

Molecular determinants of host specificity of maize-, rice- and mango-pathogenic species of the genus Fusarium

Fusarium species of the Gibberella fujikuroi species complex cause serious diseases on different crops such as rice, wheat and maize. An important group of plant pathogens is the Gibberella fujikuroi species complex (GFC) of closely related Fusarium species which are associated with specific hosts; F. verticillioides and F. proliferatum are particularly associated with maize where they can cause serious ear-, root-, and stalk rot diseases. Two other closely related species of the GFC, F. mangiferae and F. fujikuroi, which share about 90Prozent sequence identity with F. verticillioides, are pathogens on mango and rice, respectively. All of these species produce a broad spectrum of secondary metabolites such as phytohormones (gibberellins, auxins, and cytokinins), and harmful mycotoxins, such as fumonisin, fusarin C, or fusaric acid in large quantities. However, the spectrum of those mycotoxins might differ between closely related species suggesting that secondary metabolites might be determinants for host specificity. In this project, we will study the potential impact of secondary metabolites (i.e. phytohormones and certain mycotoxins) and some other species-specific factors (e.g. species-specific transcription factors) on host specificity. The recently sequenced genomes of F. mangiferae and F. fujikuroi by our groups and the planned sequencing of F. proliferatum will help to identify such determinants by genetic manipulation of the appropriate metabolic pathway(s).

Discursive fragmentation of the international forest regime complex: Towards a better understanding of multi-level forest policy discourses

This subproject aims to analyze the fragmentation of forest policy at both an international and national level for the selected countries, employing a discourse analysis approach. It is split into two sub-subprojects (SSPs). 'SSPa' conducts an analysis of discursive genealogies of forest policy in Germany, Sweden, and the US. 'SSPb' investigates the history of forest related discourses in three global environmental policy processes (UNFF, CBD, and UNFCCC). In doing so, both SSPs follow a three step procedure: In the first work package, relevant literature is reviewed and a theoretical and analytical framework is developed. In the second work package, empirical data (mostly formal and informal policy documents) are gathered and analyzed. In the third work package, emphasis is placed on the role of political 'elites' in the creation of fragmented forest policy discourses at different levels; in-depth interviews with policy stakeholders and experts add another perspective to the analysis in this work package. The project is expected to develop a new understanding not only of the fragmentation of multi-level and multi-sector forest policy discourses, but also of the way in which 'discourse elites' interact with and within these discourses. The results of the work packages will be published in peer reviewed journals and discussed with policy stakeholders and scientists in conferences and workshops.

Schwerpunktprogramm (SPP) 1833: Building a Habitable Earth, Der Einfluss atmosphärischer, biologischer und geologischer Prozesse auf die Große Sauerstoffkatastrophe

Die große Sauerstoffkatastrophe (Great Oxidation Event - GOE) kennzeichnet den starken Anstieg von molekularem Sauerstoff (O2) in der Atmosphäre während der Frühgeschichte der Erde, was flächendeckende Habitabilität ermöglicht und komplexes Leben auf der Erde erlaubt. Viele Fragen sind diesbezüglich weiterhin offen. Was dazu führte, dass sich Sauerstoff in der Atmosphäre anreicherte, der Zeitpunkt und das Ausmaß sind nicht gut bestimmt. Erst jetzt ist es möglich die komplizierten Wechselwirkungen zwischen atmosphärischen, biologischen und geologischen Prozessen zu identifizieren. Das sich daraus ergebende Absterben methanogener Lebensformen und das Auftreten eines sogenannten Schneeball-Erden-Zustandes sind Beispiele für die extremen Auswirkungen des GOE. Eine zentrale Frage, die wir untersuchen, ist ob der GOE in einem linearen oder, aufgrund einer möglichen Bistabilität von Sauerstoff, in einem sprungweisen Anstieg von O2 erfolgte. Des Weiteren studieren wir den Einfluss des Kohlenstoffzyklus und des Klimas auf die Charakteristika und den Zeitpunkt des GOE. Wir wenden unsere Erfahrung in eindimensionalen (1D) und 3D Klimamodellierungen an, um die Auswirkung unterschiedlicher Klima auf den GOE zu ermitteln. Um dies zu erreichen entwickeln und verwenden wir unser einzigartiges Atmosphärenmodell mit detailliertem Sauerstoffzyklus (inklusive zum Beispiel Verwitterungsprozesse, atmosphärische Photochemie) welches die Atmosphäre, Biosphäre und Geosphäre umfasst. Ein wichtiges Ziel ist die Analyse der Kernprozesse für den GOE unter der Berücksichtigung jüngster Ergebnisse geologischer Untersuchungen (zu zum Beispiel Oberflächendruck, atmosphärischen Treibhausgases, usw.).

Biogenic soil structures: feedbacks between bioactivity and spatial heterogeneity of water storage and fluxes from plot to hillslope scale

Soil structure determines a large part of the spatial heterogeneity in water storage and fluxes from the plot to the hillslope scale. In recent decades important progress in hydrological research has been achieved by including soil structure in hydrological models. One of the main problems herein remains the difficulty of measuring soil structure and quantifying its influence on hydrological processes. As soil structure is very often of biogenic origin (macropores), the main objective of this project is to use the influence of bioactivity and resulting soil structures to describe and support modelling of hydrological processes at different scales. Therefore, local scale bioactivity will be linked to local infiltration patterns under varying catchment conditions. At hillslope scale, the spatial distribution of bioactivity patterns will be linked to connectivity of subsurface structures to explain subsurface stormflow generation. Then we will apply species distribution modelling of key organisms in order to extrapolate the gained knowledge to the catchment scale. As on one hand, bioactivity influences the hydrological processes, but on the other hand the species distribution also depends on soil moisture contents, including the feedbacks between bioactivity and soil hydrology is pivotal for getting reliable predictions of catchment scale hydrological behavior under land use change and climate change.

Einfluss organischer Aerosole auf Luftqualität und Klima

Organische Aerosole (OA) sind wichtige Bestandteile atmosphärischer Partikel. Je nach Region können sie zwischen 20 und 90% der gesamten Submikron-Partikelmasse betragen. Dennoch sind organische Aerosolquellen, atmosphärische Prozesse und Ableitung sehr ungewiss. Vorrangiges Ziel dieses Antrages ist es, die Auswirkungen organischer Aerosole auf Luftqualität und Klima zu untersuchen. Dazu soll die Darstellung des Aerosolaufbaus und die Weiterentwicklung in einem globalen Klima-Chemie-Modell verbessert werden. Das geplante Vorhaben basiert auf einem rechnerisch effizienten Modul zur Beschreibung der Zusammensetzung und Entwicklung atmosphärischer Aerosole in der Atmosphäre (ORACLE), ein Teil des ECHAM5/MESSy (EMAC) Klima-Chemie-Modells. ORACLE wird unter Berücksichtigung aller auf Labor- und Feldmessungen basierenden neuesten Erkenntnissen und Entwicklungen aktualisiert werden, um den zunehmend oxidierenden, weniger flüchtigen und stärker hygroskopischen Charakter des organischen Aerosols während der atmosphärischen Alterung mittels Nachverfolgung ihrer beiden wichtigsten Parameter, Sättigungskonzentration und Sauerstoffgehalt, genauer darzustellen. Dieses Modellsystem soll eingesetzt werden, um die Unsicherheit hinsichtlich der Einflüsse organischer Aerosole auf die globale Luftqualität und den Strahlungsantrieb zu verringern, und zwar durch: i) Quantifizierung des relativen Beitrags der Bildung sekundärer organischer Aerosole (SOA) sowie Emissionen primärer organischer Aerosole (POA) auf den Gesamthaushalt organischer Aerosole in unterschiedlichen Umgebungen; ii) Quantifizierung des Beitrags von Biomasseverbrennung und Schadstoffemissionen sowie chemische Alterung und weiträumige Übertragung auf den Gesamthaushalt organischer Aerosole; iii) Ermittlung, inwieweit SOA Konzentrationen durch biogene und anthropogene Emissionen sowie photochemische Alterungsprozesse beeinträchtigt werden; iv) Untersuchung der Weiterentwicklung von SOA-Bildung aus natürlichen Quellen durch deren Interaktion mit anthropogenen Emissionen; v) Abschätzung der Auswirkungen photochemischer Alterungsprozesse auf die physikalisch-chemischen Eigenschaften organischer Aerosole (z.B. Hygroskopizität, Volatilität) und vi) Einschätzung der indirekten Auswirkungen organischer Aerosole auf das Klima. Vor allem aber wird der vorliegende Antrag der kommenden Generation von Chemie-Klimamodellen eine realistische Beschreibung der chemischen Entwicklung organischer Aerosole in der Atmosphäre liefern, was für die Reduzierung der Aerosol-Unsicherheiten in der Luftqualität und bei Klimasimulationen von wesentlicher Bedeutung ist. Es ist auch davon auszugehen, dass das Forschungsvorhaben wertvolle Informationen zu den Quellen und der Produktion von OA weltweit liefert, was derzeitige CCMs nicht leisten können und welche von Politikern zur Entwicklung zukünftiger wirksamer Emissionsminderungsstrategien genutzt werden können.

New Conceptual Developments and Their Implementation in the German Eco-Cycle and Waste Policies

Forschergruppe (FOR) 1740: Ein neuer Ansatz für verbesserte Abschätzungen des atlantischen Frischwasserhaushalts und von Frischwassertransporten als Teil des globalen Wasserkreislaufs, Amplitude, mechanism, and dynamical significance of salinity variability in the Atlantic and Nordic Seas, analyzed from satellite data and ocean syntheses

The goal of this project is to quantify freshwater fluxes in the ocean, and improve our understanding of their temporal and spatial changes in terms of the interaction between ocean transport processes, surface net freshwater fluxes and river run-off, as well as mixing processes in the ocean. In particular, we aim at combining all available ocean salinity/freshwater data (including novel satellite-based salinity retrievals and ARGO data), surface freshwater fluxes (including HOAPS and NCEP net surface freshwater fluxes) and river discharge with a numerical model to improve our understanding of net surface sources of freshwater, near-surface freshwater budgets, and full-depth ocean freshwater transports. Respective sub-goals entail: -Improving the quality of SMOS and Aquarius surface salinity data and estimating respective error information required for their subsequent analysis and assimilation. - Expansion of the GECCO data assimilation system to incorporate surface salinity fields. - Evaluation of the sensitivity of subsurface salinity to freshwater fluxes (incl. run-off), surface salinity fields and subsurface salinity changes. - Estimates of surface and subsurface salinity fields, ocean transports of freshwater (including surface freshwater fluxes) from monthly mean SMOS and Aquarius fields, ARGO salinities and underway salinity measurements. - Quantifying the role of surface forcing (E-P-R) versus lateral transports and mixing of freshwater in modulating the freshwater content as function of depths and geographical position. Providing a best possible description of salinity changes and underlying processes in the Atlantic Ocean.

Adaptations and counter-adaptations in the coevolutionary arms race of a baculovirus and its insect host

Cydia pomonella granulovirus (CpGV, Baculoviridae) is one of the most important agents for the control of codling moth (CM, Cydia pomonella, L.) in both biological and integrated pest management. The rapid emergence of resistance against CpGV-M, which was observed in about 40 European CM field populations from 2003 on, could be traced back to a single, dominant, sex-linked gene. Since then, resistance management has been based on mixtures of new CpGV isolates (CpGV-I12, -S), which are able to overcome this resistance. Recently, resistance even to these novel isolates was observed in CM field populations. This resistance does not follow the described dominant, sex-linked inheritance trait. At the same time, another isolate CpGV-V15 was identified showing high virulence against these resistant populations. To elucidate this novel resistance mechanism and to identify the resistance gene(s) involved, we propose a comprehensive analysis of this resistance on the cellular and genomic level of codling moth. Because of the lack of previous knowledge of the molecular mechanisms of virus resistance in insects, several different and complementary approaches will be pursued. This study will not only give an in-depth insight into the genetic possibilities for development of baculovirus resistance in CM field populations and how the virus overcomes it, but can also serve as an important model for other baculovirus-host interaction systems.

Unraveling the genetic architecture of winter hardiness and quality traits in durum by genome wide and canidate gene based association mapping

Durum wheat is mainly grown as a summer crop. An introduction of a winter form failed until now due to the difficulty to combine winter hardiness with required process quality. Winter hardiness is a complex trait, but in most regions the frost tolerance is decisive. Thereby a major QTL, which was found in T. monococcum, T.aestivum, H. vulgare and S.cereale on chromosome 5, seems especially important. With genotyping by sequencing it is now possible to make association mapping based on very high dense marker maps, which delivers new possibilities to detect main and epistatic effects. Furthermore, new sequencing techniques allow candidate gene based association mapping. The main aim of the project is to unravel the genetic architecture of frost tolerance and quality traits in durum. Thereby, the objectives are to (1) determine the genetic variance, heritability and correlations among frost tolerance and quality traits, (2) examine linkage disequilibrium and population structure, (3) investigate sequence polymorphism at candidate genes for frost tolerance, and (4) perform candidate gene based and genome wide association mapping.

Modes of vector transmission of Cherry leaf roll virus (CLRV) - molecular basis and potential arthropod vector species

Cherry leaf roll virus (CLRV) is a plant pathogen of economic and ecologic importance. It is globally distributed in a wide range of forest, fruit, and ornamental trees and shrubs. In several areas of cherry and walnut production CLRV causes severe losses in yield and quality. With current reference to the rapid dissemination and strong symptom expression in Finnish birches and the Germany-wide distribution of CLRV in birches and elderberry, we continuously investigate and gradually reveal CLRV transmission pathways as by pollen, seeds or water. However, modes and interactions responsible for the wide intergeneric host transmission as well as for the exceptional CLRV epidemic in Fennoscandia still remain unknown. In this project systematic studies shall investigate biological vectors as a causal agent to finally derive control mechanisms and strategies to avoid new epidemics in different hosts and geographic regions. Detailed monitoring of the invertebrate fauna of birch stands/forests and elderberry plantations in Germany and Finland shall reveal potential vectors to subsequently study them in detail by approved virus detection methods and transmission experiments. Molecular analyses of the CLRV coat protein shall prove its role as a viral determinant for a virus/vector interaction. Consequently, this project essentially will contribute important answers on the CLRV epidemiology, and this will be a key element within the first network of research on plant viral pathogens in forest trees.

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