Browsing by Subject "Anpassung"

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Adaptation of model organisms and environmental bacilli to glyphosate gives insight to species-specific peculiarities of the shikimate pathway
(2024) Schwedt, Inge; Commichau, Fabian M.
Glyphosate (GS), the active ingredient of the popular herbicide Roundup, inhibits the 5-enolpyruvyl shikimate-3-phosphate (EPSP) synthase of the shikimate pathway, which is present in archaea, bacteria, Apicomplexa, algae, fungi, and plants. In these organisms, the shikimate pathway is essential for de novo synthesis of aromatic amino acids, folates, quinones and other metabolites. Therefore, the GS-dependent inhibition of the EPSP synthase results in cell death. Previously, it has been observed that isolates of the soil bacteria Burkholderia anthina and Burkholderia cenocepacia are resistant to high amounts of GS. In the framework of this PhD thesis, it could be demonstrated that B. anthina isolates are not intrinsically resistant to GS. However, B. anthina rapidly adapts to the herbicide at the genome level and the characterization of GS-resistant suppressor mutants led to the discovery of a novel GS resistance mechanism. In B. anthina, the acquisition of loss-of-function mutations in the ppsR gene increases GS resistance. The ppsR gene encodes a regulator of the phosphoenolpyruvate (PEP) synthetase PpsA. In the absence of a functional PpsR protein, the bacteria synthesize more PEP, which competes with GS for binding in the active site of the EPSP synthase, increasing GS resistance. The EPSP synthase in B. anthina probably does not allow changes in the amino acid sequence as it is the case in other organisms. Indeed, the Gram-negative model organism Escherichia coli evolves GS resistance by the acquisition of mutations that either reduce the sensitivity of the EPSP synthase or increase the cellular concentration of the enzyme. Unlike E. coli, the EPSP synthase is also critical for the viability of Gram-positive model bacterium Bacillus subtilis. This observation is surprising because the enzyme belongs to the class of GS-insensitive EPSP synthases. In fact, the EPSP synthase is essential for growth of B. subtilis. The determination of the nutritional requirements allowing the growth of B. subtilis and E. coli mutants lacking EPSP synthase activity revealed that the demand for shikimate pathway intermediates is higher in the former organism. This finding explains why laboratory as well as environmental Bacilli exclusively adapt to GS by the mutational inactivation of glutamate transporter genes. Here, it was also shown that a B. subtilis mutant lacking EPSP synthase activity grows in minimal medium only when additional mutations accumulate in genes involved in the regulation of aerobic/anaerobic metabolism and central carbon metabolism. The characterization of these additional mutants will help to elucidate the peculiarities of the shikimate pathway in B. subtilis. Moreover, the mutants could be useful to identify the aromatic amino acid transporters that still await their discovery.
Assessment of phenotypic, genomic and novel approaches for soybean breeding in Central Europe
(2022) Zhu, Xintian; Würschum, Tobias
Soybean is the economically most important leguminous crop worldwide and serves as a main source of plant protein for human nutrition and animal feed. Europe is dependent on plant protein imports and the EU protein self-sufficiency, which is an issue that has been on the political agenda for several decades, has recently received renewed interest. The protein imports are mainly in the form of soybean meal, and soybean therefore appears well-suited to mitigate the protein deficit in Europe. This, however, requires an improvement of soybean production as well as an expansion of soybean cultivation and thus breeding of new cultivars that combine agronomic performance with adaptation to the climatic conditions in Central Europe. The objective of this thesis was to characterize, evaluate and devise approaches that can improve the efficiency of soybean breeding. Breeding is essentially the generation of new genetic variation and the subsequent selection of superior genotypes as candidates for new cultivars. The process of selection can be supported by marker-assisted or genomic selection, which are both based on molecular markers. A first step towards the utilization of these approaches in breeding is the characterization of the genetic architecture underlying the target traits. In this study, we therefore performed QTL mapping for six target traits in a large population of 944 recombinant inbred lines from eight biparental families. The results showed that some major-effect QTL are present that could be utilized in marker-assisted selection, but in general the target traits are quantitatively inherited. For such traits controlled by numerous small-effect QTL, genomic selection has proven as a powerful tool to assist selection in breeding programs. We therefore also evaluated the genomic prediction accuracy and found this to be high and promising for the six traits of interest. In conclusion, these results illustrated the potential of genomic selection for soybean breeding programs, but a potential limitation of this approach are the costs required for genotyping with molecular markers. Phenomic selection is an alternative approach that uses near-infrared or other spectral data for prediction instead of the marker data used for its genomic counterpart. Here, we evaluated the phenomic predictive ability in soybean as well as in triticale and maize. Phenomic prediction based on near-infrared spectroscopy (NIRS) of seeds showed a comparable or even slightly higher predictive ability than genomic prediction. Collectively, our results illustrate the potential of phenomic selection for breeding of complex traits in soybean and other crops. The advantage of this approach is that NIRS data are often available anyhow and can be generated with much lower costs than the molecular marker data, also in high-throughput required to screen the large numbers of selection candidates in breeding programs. Soybean is a short-day plant originating from temperate China, and thus adaptation to the climatic conditions of Central Europe is a major breeding goal. In this study, we established a large diversity panel of 1,503 early-maturing soybeans, comprising of European breeding material and accessions from genebanks. This panel was evaluated in six environments, which revealed valuable genetic variation that can be introgressed into our breeding programs. In addition, we deciphered the genetic architecture of the adaptation traits flowering time and maturity. Taken together, the findings of this study show the potential of several phenotypic, genomic and novel approaches that can be integrated to improve the efficiency of soybean breeding and thus hold great promise to assist the expansion of soybean cultivation in Central Europe through breeding of adapted and agronomically improved cultivars.
Berufliche Identitätsentwicklung und Laufbahnadaptabilität : Zentrale Faktoren der beruflichen Entwicklung kaufmännischer Auszubildender
(2023) Kirchknopf, Sebastian; Kögler, Kristina
Against the background of the challenges for individual career development, with regard to increasing work-related flexibilization, self-direction, and subjectification, vocational identity and career adaptability have been established as central variables of modern career development (Savickas 2011). In this context, both constructs are often depicted as interrelated, with (vocational) identity having a certain orientation function with respect to career adaptation and career development processes, while (career) adaptability encompasses the necessary dispositions and resources for the required adaptation and reorientation efforts (Hall 2004; Fugate et al 2004). The construct of vocational identity has long been an integral part within the discourse of vocational and business education, as it is considered to be of high importance for the development of professional competence as well as for the socialisation of vocational learners (Lempert 2009). In contrast, the concept of adaptability has received much less attention from the perspective of vocational and business education, although its importance for the understanding of vocational adaptation and integration processes has been discussed in the international context for a long time (Savickas 1997, 2005). In relation to vocational identity, it seems essential to consider whether career adaptability in the VET context can be understood as a beneficial element of vocational integration (Savickas 2013) or rather as a professional flexibility and mobility orientation that tends to be associated with low work-related attachment (Briscoe/Hall 2006). For a closer look at the interaction of both constructs in the context of commercial vocational training, however, a clarification of the conceptual approach to vocational identity as well as the content-related specifics of the identity construction and development of commercial trainees is also indicated. In order to investigate the relevance of vocational identity and career adaptability for the professional development of commercial trainees, several research questions were derived. In addition to a theoretical clarification of the respective conceptual understandings, these include an empirical approach in qualitative and quantitative terms. To answer the research questions, a cumulative research design was chosen, comprising a total of four papers. From a theoretical and conceptual perspective, it was possible to deduce that – beyond previous reference points of the field of vocational and business education – there is a high significance of career adaptability especially for the professional development processes of learners within initial vocational training. In the course of the subsequent examination of its empirical suitability for the context of vocational education, Savickas concept of career adaptability proved to be particularly promising. Its four-dimensional structure could be replicated among commercial apprentices, and it could be distinguished from more disintegrative conceptualisations of adaptability. With regard to the development of vocational identity among commercial apprentices, an overarching characteristic identified was a decline in occupational and organisational identification during the course of their apprenticeship, which in turn affect their occupational and organisational dropout intentions. The qualitative analysis also revealed occupation-specific characteristics that suggest that identification potentials can be found in both generalised and more specialised commercial apprenticeships, but that these potentials can differ significantly (e.g., career perspectives vs. affectively significant activities). Ultimately, the positive correlation between career adaptability and the professional identity of commercial apprentices could be demonstrated, which points to the beneficial effect of career adaptability for professional development and for building work-related ties in the context of vocational learning.
Climate change and agricultural structural change : the relevance for machinery use and acquisition in Germany
(2021) Mendoza Tijerino, Francisco Antonio; Berger, Thomas
This thesis is a contribution to the research project “Regional Climate Change,” funded by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG – Forschergruppe 1695 Regionaler Klimawandel). The projects objective was to learn about the vulnerability and sensitivity of typical land systems in Southwest Germany and identify suitable strategies for adaptation. The doctoral work contributes with empirical and methodological insights of farmers likely management adaptations in light of the farm managerial challenges arising from climate and structural change in Germany. The agricultural structure in Germany has strongly changed in the last 60 years. Where before numerous small-scale and labor-intensive farms were observed, it is now the place where fewer and highly mechanized farms contribute to agricultural production. The ongoing agricultural structural change in Germany is characterized by a trend in which many farms exit the agricultural sector, and the remaining --growth-oriented-- farmers take over the land, reorganize their farm business, and expand their operations. Nevertheless, this trend of farm growth, which is expected to continue in the future, poses significant challenges at the farm management level: Decisions on machinery use and acquisition play a crucial role in shaping the farm cost structure, and represent a critical element for maintaining competitiveness. Particularly for the expansion efforts, farm managers face a highly complex decision-making process to acquire the proper machinery capacities for field operations. Moreover, an additional factor will need to be considered for adequate decision-making: Climate change developments and the uncertainties associated with this process will likely increase the complexity of the farmers decision-making regarding the best reorganizational strategies towards farms expansion. Changes in the natural conditions for crop growth and development will likely result in management adaptations, e.g., changing the timing for fieldwork operations or changing land-use patterns. An analysis of the complex interactions and interdependencies between the environment and the farm system, on the one hand, and the resources and production possibilities available to the farm manager in the course of farm expansion on the other hand, require adequate tools of analysis. This work analyzes three dimensions of farm machinery management in the context of climate change and agricultural structural change. The first element of analysis corresponds to an examination of the sensibility of land-use and machinery investment decisions to climate change scenarios with the agent-based MPMAS model constructed for Central Swabian Jura in Southwest Germany. The Central Swabian Jura MPMAS model is a constitutive part of the bioeconomic modeling system MPMAS_XN. The MPMAS_XN system integrates the agricultural economic agent-based software MPMAS and the plant-soil modeling software Expert-N (XN) into a fully coupled system. The assessment of the sensibility and responsiveness of the MPMAS component revealed complex adaptation responses of land-use and machinery investment decisions as a result of shifted timing in fieldwork operations (e.g., harvesting or fertilization tasks). The second element of analysis corresponds to an examination of economies of size arising from farm machinery use and acquisition decisions in arable farms that follow a typical crop rotation practiced in Germany. For the analysis, a whole-farm multiperiod mathematical program implemented in the agent-based software MPMAS was employed. Optimizations were run and evaluated at a broad range of farm sizes and two distinctive distributions of availability of fieldwork days estimated for Southwest Germany. The results allowed observing patterns of optimal farm machinery demand and cost curves for several evaluated farm sizes and distributions of available fieldwork days distributions. The third main element of this work corresponds to a methodological contribution to the MPMAS_XN model system. Within this element, the implementation, functioning, and potential of an external theory-based MPMAS module are presented. The external module represents dynamics for joint machinery investments among simulated farm agents and serves as an enhancing methodological contribution for analyzing and representing farm machinery management in the agent-based software MPMAS.
Developing cropping systems for the ancient grain chia (Salvia hispanica L.) in two contrasting environments in Egypt and Germany
(2020) Mack, Laura; Graeff-Hönninger, Simone
Chia (Salvia hispanica L.) seeds have been revived as functional “superfood” for human nourishment especially for vegan and vegetarian diets and are becoming increasingly widespread and present in new food products in Europe. The seeds are beneficial because of being gluten-free, containing antioxidants and a high concentration of α-linolenic acid, and having a high content of dietary fiber and high-quality protein. Chia is originally adapted to short-day conditions and grows naturally in tropical and subtropical environments. Nevertheless, it can survive under water stress and could, therefore, be cultivated in arid regions. Egypt has been classified as a water-scarce state. Due to its drought tolerance, chia might contribute to saving the scarce source “water” in Egypt and offer the chance to export these high value seeds, generating foreign exchange for reimporting e.g. wheat characterized by a higher water demand. Worldwide, the biggest problems and key challenges under climate change (CC) are water and food security in arid and semiarid regions. In the future, CC and water scarcity will significantly threaten agriculture and sustainable development. A rising population requires on the one hand an increase in food grain production, but also a change toward environmentally sound sustainable agriculture. Chia has been suggested as a favorably economic alternative for common field crops sustaining diversification and stabilization of the local agricultural economy. However, broad experience in growing chia in new environments is missing. The agronomic management has not been improved from formerly small-scale production systems. Most of the previous studies focused on seed characteristics. Information on fertilization, plant protection, and improved varieties is scarce, which are reasons for its low productivity in the countries of origin. Field experiments were conducted at the experimental station “Ihinger Hof” of the University of Hohenheim in southwestern Germany from 2015 to 2017 and in Egypt during the cropping season 2015 to 2016 at SEKEM’s experimental station located 50 km Northeast of Cairo. The present doctoral thesis was based on a project embedded in the graduate school Water-People-Agriculture (WPA) at the University of Hohenheim funded by the Anton-&-Petra-Ehrmann foundation that focuses on key water issues and water related challenges of todays society. On a final note, the main results of this thesis provide further information and expanded knowledge on chia cultivation in two contrasting environments (including a desert region) out of its center of origin. Overall, the current doctoral thesis presents a combined approach of experimental field research and crop modeling to support the optimization of farming practices of chia in new environments. A universal and nondestructive LA estimation model for chia was developed. Further, the CROPGRO model was adapted for chia to provide a preliminary model for a realistic simulation of crop growth variables. The approaches presented in this thesis may contribute to testing new environments for chia cultivation and to improving its production. Moreover, this study helped to develop further general model source codes to simulate the growth of tiny seeds. The adaptation to other Salvias should be much easier with this developed model. Future research requirements and issues requiring model improvement such as N-response and the development of code relationships that can simulate parameters of seed quality could improve the plant growth model for chia.
Growth regulation of ornamental and vegetable plants under greenhouse conditions by air stream-based mechanical stimulation
(2022) Sparke, Marc-André; Müller, Joachim
Plant growth regulation is an integral part within the production chain of ornamentals and vegetable seedlings. In protected ornamental horticulture, chemical-synthetic plant growth regulators (PGR) are used to reduce plant size. In vegetable production, the use of these substances is prohibited by law in most counties, which is why non-chemical growth regulation methods must be applied. In this respect, a production method for non-chemical growth control of ornamentals and vegetable seedlings under greenhouse conditions has been developed that is based on the application of air streams, inducing thigmomorphogenesis, the morphological and structural shaping of a plant organism during its development phase as influenced by touch-like stimuli. In own experiments jointly performed at the State Horticulture College and Research Station in Heidelberg, Germany, the application of a regularly applied air stimuli significantly reduced plant height by 24% in bellflower (Campanula ‘Merrybell’) compared to the control. In a subsequent practical trial at a local horticulture company (Fleischle GbR, Vaihingen Ensingen, Germany) plant height of creeping inchplant (Callisia repens) was significantly reduced by 20% on average compared to the control. In both experiments, a compressor generated the air stream which was then applied to the plant stand through custom-built stainless-steel nozzles (air pressure module). In tomato (Solanum lycopersicum ‘Romello’), air streams applied by the ‘air knife’ module, the ‘360° rotor’ module, or the ‘air pressure’ module resulted in a reduction in plant height of 26%, 33%, and 36% compared to the control, respectively. The air stream guided into the air knife module was applied by an aperture slot, which could be adjusted between 1 and 5 mm, while the air stream guided into the 360° rotor module was applied via two 360° rotating PVC tubes that were inserted on the bottom of a rectangular aluminium box. It turned out, that the air outlet velocity along the aperture slot of the air knife module was highly variable. Consequently, the stimulus intensity perceived by individual experimental plants was unequal. A multiple regression analysis clearly showed that the maximum air velocity explained the variability in plant height reduction by air streams generated with the air knife module best, while the stimulus duration and the cumulative air velocity were less relevant. Plant height reduction by air stream generated with the 360° rotor module was most homogenous compared to the other prototypes. Therefore, a subsequent series of experiments at the University of Hohenheim, Stuttgart, Germany, was carried out with the most promising prototype, the 360° rotor. No systematic dose-response relationship related to increasing application frequencies of 8, 24, 40, 56, 72, and 80 d-1 was found, confirming previous findings that the plants do not integrate the mechanical stimulus over time. In contrast, plant height reduction was significantly influenced by the air stream velocity. A sigmoidal dose-response relationship was fitted to the data and showed negligible effects on tomato plant height reduction between 0.7 m s-1 and 2.0 m s-1, followed by a steep increase in the reduction effect up to 4.7 m s-1 and a fading of the effect at 36 % reduction for air velocities beyond that. With the optimised settings for daily application frequency and air velocity, another experiment was conducted focusing on the effect of air stream application on phenotypic and physiological responses in tomato. Air stream application resulted in a gradual reduction of total leaf area by 14% on day 14 after treatment start, and radial growth was promoted relative to internode elongation compared to the untreated control, resulting in a more compact and stable plant phenotype. Air stream-treated plants translocated proportionally more assimilates to leaves and stems, at the expense of dry matter accumulation to petioles. The reduction in total leaf area was compensated by an increased leaf density, accompanied by a higher leaf green intensity and consequently by an average 8% increase in net CO2 assimilation rates compared to the control. Thus, air stream-treated plants partially sustained total biomass accumulation at the same level as compared to the control.
Molecular evidence of intraclonal variation and implications for adaptational traits of grape phylloxera populations (Daktulosphaira vitifoliae, Fitch)
(2007) Vorwerk, Sonja; Blaich, Rolf
Grape phylloxera (Daktulosphaira vitifoliae Fitch; Homoptera: Phylloxeridae) is an economical important insect pest of grapevine (Vitis spp.) worldwide. The insect was introduced with contaminated plant material from North America in the 1850s and spread rapidly across all European viticultural regions. In the 19th century, nearly three-forths of the ungrafted and highly susceptible European grape species were destroyed by the insect pest. European viticulture did not recover until the development of grafting, combining European Vitis vinifera varieties with resistant rootstocks, bred from American Vitis species. Grape phylloxera is still present in viticulture. Today, grape phylloxera populations mainly persist in abandoned vineyards and rootstock nurseries. Grape phylloxera populations seem to be variable in terms of genotypic composition and host adaptability. The lifecycle described by Fitch (1854) and others in the 19th century does not seem to match actual conditions anymore. This thesis aimed at redefining the genetic structure of European grape phylloxera populations by employing genetic markers. It was shown, that the insect has turned away from its classical holocycle and now mainly reproduces asexually, as already demonstrated for Australian grape phylloxera populations. Despite asexual reproduction, all examined populations revealed a high grade of genotypic diversity. The reports on the emergence of new and more aggressive strains raised the question, how a population composed of asexually reproducing organisms would change and adapt to such an extent. Using a multilocus marker system, eight single founder lineages were genetically monitored over at least 15 generations. All lineages revealed a high grade of intraclonal variation. Sequencing of polymorphic fragments showed, that the genetic variation was not due to contaminating plant or bacterial DNA, but was due to variation within the insect genome. Furthermore, mutations occured already in early generations and were not observed to accumulate in later generations. Mutations were rather generated constantly and only few mutation specific markers were identified to be stable over all following generations. The here documentated genetic variation reveals the great adaptational potential of this insect pest. The adaptability of single founder lineages was further assessed by measuring physiological parameters in single isolation chambers in the greenhouse. Parameters as the number of surviving individuals per generation, the number of eggs or the number of ovarioles per generation exposed differences in performance among the lineages and also within the lineages a high grade of intraclonal variation. A direct correlation of specific multilocus markers and particularly adapted individuals or lineages was not possible in this assay. Two markers, though, were observed to occure in several lineages which performed well on the new host plant. These markers may be a first step to the development of adaptation-related markers and need to be tested on further populations and host plants. When analysing intraclonal variation, the question of putative contaminating factors within the system arises. Symbiotic bacteria occuring in nearly all aphid species certainly are the first to be suspected as a source of genetic variation among single individuals tested. Endosymbiotic bacteria, as Buchnera aphidicola in other aphid species, influencing nutritional condition and fitness of the insect population, were not identified in D. vitifoliae. A bacterium, closely related to Pantoea agglomerans, however, was identified in several grape phylloxera populations, using universal 16S rDNA primers and later specifically developed markers, which were also employed for in situ hybridization. The bacterium was localized in the salivary pump of D. vitifoliae. PCR analysis of in vitro reared populations revealed that the bacterium is present in root- and leaf-feeding parthenogenetic populations of grape phylloxera and, moreover, seems to be transmitted from generation to generation. In other insect species, this bacterium has been demonstrated to produce antifungal and antibacterial substances, which were also found in first in vitro tests with grape phylloxera associated bacteria. The insect may benefit from the antagonistic potential of these bacteria. P. agglomerans may be a further participant in the certainly complex interaction of grape phylloxera and grapevine. This thesis represents a broad approach to elucidate the development of grape phylloxera populations in Europe. Using new molecular marker systems, it has become possible to gain more information on the genetic structure of the insect and its adaptational potential. The predominant clonal reproduction mode of the insect confronts grapevine breeders and pest management with the task to continously develop new resistant rootstocks and to keep up with new pest management systems.
Phenotypic and genomics-assisted breeding of soybean for Central Europe : from environmental adaptation to tofu traits
(2022) Kurasch, Alena; Würschum, Tobias
Soybean (Glycine max Merr.) is one of the major crops in the world providing an important source of protein and oil for food and feed; however it is still a minor crop in Central Europe. Soybean cultivation can play an important role in a more sustainable agricultural system by increasing local and regional protein production in Europe. The demand for locally produced soybean products is still growing in Europe. The key for a successful establishment of soybean cultivation in Europe is adaptation of soybean varieties to the Central European growing conditions. For the latitudinal adaptation to long-day conditions in Central to Northern Europe, an adapted early flowering and maturity time is of crucial importance for a profitable cultivation. The key traits flowering and maturity are quantitatively inherited and mainly affected by photoperiod responsiveness and temperature sensitivity. The most important loci for an early flowering and maturity are E1-E4 and the various allelic combinations condition soybean flowering and maturity time and therefore strongly contribute to the wide adaptability (Jiang et al., 2014; Tsubokura et al., 2014; M. Xu et al., 2013). Besides the main usage as protein source for animal feeding, soybean is also a very valuable source for human consumption. Tofu is enjoying ever greater popularity in Europe, as it is one of the best sources of plant protein with additional health benefits, rich in essential amino acids, beneficial lipids, vitamins, and minerals, as well as other bioactive compounds, such as isoflavones, soyasaponin, and others, (Lima et al., 2017; Zhang et al., 2018). Thus, plant breeding has to provide not only well-adapted varieties with good agronomic and quality properties, but also provide varieties well-suited to the further processing into soymilk and tofu. Therefore, a good knowledge about the breeding target, how to assess it and how it is inherited is crucial. The conducted studies covered a broad range of aspects relevant to improve a soybean breeding program. By combining environmental analysis, E-gene analysis, genomic approaches (QTL mapping and genomic prediction), and tofu phenotyping, breeder decisions become more accurate and targeted in the way of selection thereby increasing the genetic gain. In addition, combining the results of the different aspects helps to optimize the resources of a breeding program. Increasing the knowledge about the different aspects from environment to tofu QTL enables a breeder to be more precise and focused. But the more targeted and specific, the more complex a breeding program gets, which requires adequate tools to handle all the different information in a meaningful and efficient way to enable a quick and precise breeding decision.