Institut für Kulturpflanzenwissenschaften

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Grasping the complexity of intercropping - developing and testing an integrated decision support system for vegetable production in the North China Plain
(2010) Feike, Til; Claupein, Wilhelm
This cumulative dissertation consists of six papers published, accepted or submitted to international high standard journals or books. To detect and describe the status quo of vegetable intercropping in the North China Plain (NCP), a survey was conducted from autumn 2007 to spring 2008. The results of the interviews with researchers, extensionists and farmers embedded in the first article revealed a huge variety of intercropping systems being practiced by farmers in the region. The first article furthermore elaborated farmers? underlying motives and concepts and described the knowledge transfer systems involved. When evaluating the prevailing systems against the background of the rapidly changing socio-economic frame conditions for farming in rural China, it became obvious that a great proportion of the systems practiced nowadays are prone to extinction in a long run. Therefore the second article discussed possible adjustments of the intercropping systems to fit the demands of modern agriculture, while maintaining their potential agronomic and environmental benefits. To enable mechanization, it was suggested to either adjust the machinery to the traditional row intercropping systems, or adjust the cropping system to the prevailing and available machinery. The latter approach was then followed throughout the thesis, using an agronomic modeling approach. The combination of Chinese cabbage and maize was selected, as it is a traditional intercropping system, with strong interspecific effects. In the course of this study, the two crops were strip intercropped in four field experiments at three sites in Germany and in China in 2008 and 2009. To understand, explain and predict plant behavior under the impact of complex cropping structures, crop growth models present a viable and powerful tool. However, two constrains had to be overcome within the framework of this thesis i) Chinese cabbage is not integrated in the common process-oriented crop growth models, ii) a method had to be developed to quantify resource competition and simulate intercropping. Therefore the integration of Chinese cabbage, the number one field vegetable of China, into the CROPGRO model constituted the first step for the simulation of intercropping systems in China. Two greenhouse experiments, testing crop growth and development under different temperature regimes, served as the data base for the accurate parameterization of Chinese cabbage and built the baseline for the third article. Cardinal temperatures of Chinese cabbage were identified by correlating mean relative growth rates and mean leaf appearance rates to temperature. Minimum growth temperature was identified at 0 °C, optimum temperature ranges between 14 °C and 24 °C, and maximum temperature is 34 °C. The further adjustment and testing of the model, which was executed on up to six independent data sets, is presented in the fourth article. The key to successfully simulate intercropping systems is the knowledge on changes in resource availability compared to monocropping. Therefore, a method was developed to quantify the availability of the most crucial growth factor solar radiation at any location within a Chinese cabbage strip, presented in the fifth article. The method was extended in the sixth and final article to enable the estimation of available radiation in Chinese cabbage strips of different widths. The ?environmental modifications? option of CROPGRO was employed to simulate the effects of the estimated reduction in incoming radiation in Chinese cabbage strips of different width. Simulations were conducted over up to thirty years of weather data of 12 locations throughout the NCP, and were additionally tested on different soil texture types. The results were extended over the entire NCP by linking them to a GIS-system. The developed approach constitutes a reliable decision support for the optimization of the spatial arrangements in Chinese cabbage strip intercropping systems, according to local soil and climate conditions. The described approach can be extended to develop a comprehensive decision support system that allows testing of various intercrop combinations under a wide range of climate and especially radiation environments. The presented thesis is a valuable contribution to the development of sustainable vegetable production systems in the NCP. A new method to quantify availability of solar radiation in strip intercropping was developed, which can be applied in various other intercropping systems. The integration of Chinese cabbage into CROPGRO, offers great opportunities not only for studying intercropping systems, but also for improving input levels and resource use efficiency in Chinese cabbage production in China and throughout the world. Understanding farmers? concepts and estimating the production potential of intercropped Chinese cabbage created additional value, which substantially contributes to realizing the potential of intercropping in the NCP.
Designing, modeling, and evaluation of improved cropping strategies and multi-level interactions in intercropping systems in the North China Plain
(2010) Knörzer, Heike; Claupein, Wilhelm
Adjusting cropping systems in order to increase their efficiency is a global issue. High yield and sustainability are the catchphrases of production in the 21st century, and agricultural production has to solve the balancing act between ecology and economy. Therefore, the requests for farmers, consultants and researchers are rising, and production modes are changing. Nevertheless, solutions have to be detected spatially explicit and locally adapted and accepted in order to be implemented successfully. Taking the North China Plain as an example, the productivity of arable land needs to be further increased by applying strategies to reduce or avoid negative environmental effects. Further yield increases are not possible by increasing input factors like N-fertilizer or irrigation water as N-fertilizer rates are extremely high and irrigation water is limited. However, yield increases might be possible by developing improved cropping strategies operated by cropping designs. Taking modeling and simulation tools into account back up the acceleration of research attainments and the understanding of cropping systems. The present thesis embraces the designing and modeling of such a potential cropping system, to wit strip intercropping. Thus, the main goals of the study were to analyze, design, evaluate, and in the end model intercropping. Intercropping systems are complex systems which strongly need to be designed and evaluated carefully in order to fulfill the premises of ecological and economical efficiency as well as sustainability. Multi-level interactions have to be weighted and taken into regard for evaluating datasets applicative for modeling and simulating intercropping. The main results of the study indicated, that traditional cropping systems like intercropping are widespread in China, where approximately one third of arable land is under intercropping. Reviewing cereal intercropping systems in China, the four agro-ecological regions ?Northeast and North?, the ?Northwest?, the ?Yellow-Huai River Valley? and the ?Southwest? could be classified, distinguished and described. Intercropping offers a great variation of species combination, benefits as well as challenges for cropping systems design and farmers. Carefully balanced between facilitation and competition, intercropping bears the potential of increased yield and yield stability, income security, resource use efficiency and biodiversity. Intercropping gives evidence about traditional cropping systems with the potential for future production systems under the paradigm of sustainability. Further, results from conducted field experiments indicated that border effects are the key component of intercropping performance. Nevertheless, analyzing strip intercropping statistically has peculiarities as they lack in randomization because the cropping system imposes alternating strips. Thus, spatial variability and its effect on yield were regarded differently within a geo-statistical analysis. In addition to the geo-statistical analysis, the crop growth modeling approach paid tribute to monocropping effects as well as to field border effects occurring in strip intercropping systems. Further on a model-based approach was tested to quantify multi-level interactions with special regard to changing microclimatic conditions and to optimize intercropping systems from an agronomical point of view. In comparison to other interspecific competition modeling approaches, a shading algorithm was evaluated and implemented into the process-oriented crop growth model DSSAT in order to simulate competition for solar radiation. More common in modeling mixed intercropping, a modified Beer?s law subroutine has been used instead, e.g. in APSIM. APSIM and DSSAT were compared by modeling the conducted field trials. As a result, the Beer?s law approach was not capable to model strip intercropping. In contrast, the modeling with a changed DSSAT model showed that applying a simple shading algorithm that estimated the proportion of shading in comparison to the monocropping situation and in dependency from neighboring plant height seems to be a promising approach. The results indicated that competition for solar radiation in those systems is a driving force for crop productivity but neither the most dominant nor the one and only. Resource distribution and allocation in space and time seems to be more important than the total amount of resources. Those effects have to be taken into account when simulating interspecific competition.
Rhizosphere processes as determinants for glyphosate damage of non-target plants
(2010) Bott, Sebastian; Neumann, Günter
Due to low production costs and high herbicidal efficiency, glyphosate is the most widely used wide-spectrum herbicide. Glyphosate acts as a non-selective, total herbicide by inhibiting the biosynthesis of aromatic amino acids. Apart from glyphosate drift contamination, risks of glyphosate toxicity to crop plants and other non-target organisms are generally considered as marginal, because glyphosate is almost instantaneously inactivated by adsorption to the soil matrix and rapid microbial/chemical degradation in the soil solution. However, in the recent past, an increasing number of yet unexplained observations on significant damage of crop plants have been reported in the literature and by farmers, suggesting gaps in the risk assessment, with respect to the fate glyphosate in the rhizosphere and the interaction with rhizosphere processes. According to these observations, the aim of present study was a systematic evaluation of potential rhizosphere effects of glyphosate, including direct toxicity, risks of re-mobilisation by fertiliser application, potential role of pathogens and allelopathic compounds, and interactions with micronutrients, both in glyphosate-sensitive and transgenic glyphosate-resistant crops. A series of field trials in reduced soil tillage cropping systems as well as green-house experiments on soils with contrasting properties with sunflower, winter wheat and soybean, consistently revealed a close clausal relationship between crop damage and (a) short waiting times between glyphosate application on target weeds and subsequent sowing of crops and (b) the density and speed of decay of glyphosate-treated weeds. The results suggested that damage of crop plants is induced by a rhizosphere transfer of glyphosate from weeds to subsequently sown crops. This transfer might take place by contact contamination due to exudation of glyphosate from living roots of treated weeds and/or release during decomposition of the root residues. A comparison between phytotoxic effects of glyphosate and aminomethylphosphonic acid (AMPA) as major metabolite of glyphosate in soils, revealed high toxicity in case of root exposure to glyphosate, but not to AMPA. By contrast, a significant decline of germination was induced by seed exposure to AMPA, while germination was not affected by glyphosate treatments. The observed differences in sensitivity to glyphosate and AMPA in different stages of plant development may explain variable symptoms of crop damage under field conditions, ranging from growth depressions and chlorosis to reduced field emergence. The results of the present study further suggest that risks for crop damage associated with rhizosphere transfer of glyphosate are additionally influenced by a range of environmental factors, such as growth season (spring or fall application), temperature, soil moisture, redox potential of soils and soil microbial activity. These factors might shorten or prolongate the time window for crop damage of glyphosate contact contamination in the rhizosphere under field conditions. Model experiments investigating the sensitivity of different plant species to glyphosate root exposure, revealed significant differences between winter wheat, maize and soybean in terms of glyphosate-induced plant damage but also in their ability for recovery from glyphosate damage suggesting marked genotypic differences in the expression of damage symptoms also under field conditions. In agreement with previous investigations, results of the present study indicated a rapid inactivation of glyphosate by adsorption to the soil matrix. Glyphosate adsorption in soils seem to be mainly mediated by the phosphonate group of the molecule in a way similar to the adsorption of inorganic phosphate. Accordingly glyphosate re-mobilisation is possible via ligand exchange by phosphate application. The results of the present study have demonstrated for the first time that depending on soil properties also the application of fertiliser phosphate is able to re-mobilise glyphosate in sufficient quantities to mediate crop damage in pot experiments. This finding suggest, that re-mobilisation of glyphosate potentially by fertiliser P or root-induced chemical modifications for P and Fe mobilisation needs to be considered as additional potential rhizosphere pathway for glyphosate damage to non-target plants. Field trials and model experiments under soil and hydroponic conditions consistently revealed a significantly impaired nutritional status of glyphosate-sensitive but also glyphosate-resistant crops. However, depending on the culture conditions different mineral nutrients were affected by the glyphosate treatments and plant damage was not related with a certain nutrient deficiency. These findings suggest that damaged root growth, induced by glyphosate toxicity, rather than specific interactions with certain mineral nutrients are responsible for the observed impairment of nutrient acquisition. In conclusion, results of the present study highlight that risks for crop damage associated with glyphosate toxicity in the rhizosphere can be substantial and is influenced by factors such as waiting time after herbicide application, weed density, cropping systems, fertilizer management, genotypic differences, and probably also environmental factors including temperature, soil moisture, and soil microbial activity. The independency between these factors is so far not entirely clear but should be investigated in future studies. Nevertheless, results of present study suggest that risks could be minimized by simple management tools such as the consideration of waiting times between application of glyphosate and sowing of crops particularly in case of high weed densities and alternation of herbicides to reduce not only risk for remobilization of glyphosate but also problems associated to the selection of glyphosate-resistant weeds.
Biometrical tools for heterosis research
(2010) Schützenmeister, André; Piepho, Hans-Peter
Molecular biological technologies are frequently applied for heterosis research. Large datasets are generated, which are usually analyzed with linear models or linear mixed models. Both types of model make a number of assumptions, and it is important to ensure that the underlying theory applies for datasets at hand. Simultaneous violation of the normality and homoscedasticity assumptions in the linear model setup can produce highly misleading results of associated t- and F-tests. Linear mixed models assume multivariate normality of random effects and errors. These distributional assumptions enable (restricted) maximum likelihood based procedures for estimating variance components. Violations of these assumptions lead to results, which are unreliable and, thus, are potentially misleading. A simulation-based approach for the residual analysis of linear models is introduced, which is extended to linear mixed models. Based on simulation results, the concept of simultaneous tolerance bounds is developed, which facilitates assessing various diagnostic plots. This is exemplified by applying the approach to the residual analysis of different datasets, comparing results to those of other authors. It is shown that the approach is also beneficial, when applied to formal significance tests, which may be used for assessing model assumptions as well. This is supported by the results of a simulation study, where various alternative, non-normal distributions were used for generating data of various experimental designs of varying complexity. For linear mixed models, where studentized residuals are not pivotal quantities, as is the case for linear models, a simulation study is employed for assessing whether the nominal error rate under the null hypothesis complies with the expected nominal error rate. Furthermore, a novel step within the preprocessing pipeline of two-color cDNA microarray data is introduced. The additional step comprises spatial smoothing of microarray background intensities. It is investigated whether anisotropic correlation models need to be employed or isotropic models are sufficient. A self-versus-self dataset with superimposed sets of simulated, differentially expressed genes is used to demonstrate several beneficial features of background smoothing. In combination with background correction algorithms, which avoid negative intensities and which have already been shown to be superior, this additional step increases the power in finding differentially expressed genes, lowers the number of false positive results, and increases the accuracy of estimated fold changes.
Premature fruit drop in mango (Mangifera indica L.) in Northern Vietnam
(2011) Roemer, Malte G.; Wünsche, Jens Norbert
Mango production in Northern Vietnam is mainly organized in farmer-owned, small-scale orchard operations. However, the production is limited due to excessive fruit drop presumably caused by unfavourable climatic conditions in combination with plant stresses during the fruit set period. There is a general belief that this phenomenon is caused by different combinations of stressing factors which may vary between regions and sites. In the mountainous area of Northern Vietnam, fruit drop of two main local cultivars ?Hôi? and ?Tròn? may be caused by environmental cues occurring particulary during fruit set. Environemntal stress factors may include excessive air temperature, low relative humidity, strong prevailing winds and little rainfall. These multiple stressors are likely associated with a time dependent change of the endogenous plant hormone auxin (indole-3-acetic acid, IAA) exported from fruit and within the pedicel. Field trials revealed, that fruit shedding could be reduced by irrigation and plant growth regulator (PGR) application throughout the 3-year experiment study; however, it remains unclear how climatic conditons might induce hormonal response and thus enhance fruit shedding at different stages of fruit development. The present research project consists of three studies. First it was to determined which single or multiple climatic cues trigger fruit shedding in mango. Second, it was attempted to alleviate fruit abscission by PGR spray application at post-bloom and early developmental stages of the fruit in comparison with regular irrigation scheduling to reduce extensive fruit abscission. Third, the morphological changes in the abscission zone of mango pedicel during fruit abscission were studied. The timely changes of plant tissue IAA concentration and its key role in the abscission process was also evaluated. The research work was conducted in a commercial orchard near the township of Yen Chau in 2007, 2008 and 2009. The experimental design consisted of 20 randomly selected 10-year-old mango trees of each of the cultivars ?Hôi? and ?Tròn?. Half of the trees were irrigated at 3-day-intervals by mircospinkler and the remaining trees served as non-irrigated controls. For the PGR applications, 3 trees of each cultivar in 2008, and 6 trees of each cultivar in 2009 were used. In both experiments, 10 randomly selected inflorescences per tree were labelled and counted twice per until end of the fruit drop period. Fruit tissue was collected on-site from irrigated and non-irrigated trees. The fruit export of the endogenous indole-3-acetic acid was analyzed by Radio-Immuno-Assay (RIA). Further, to clarify the morphological changes within the abscission zone (AZ) of mango pedicels, samples of irrigated and control trees were collected, fixed and embedded, using a modified dehydration and embedding technique by vacuum infiltration. The results of the first part of this study indicate that the onset of the hot, dry prevailing winds induced the fruit drop. Whether fruit drop was reduced by irrigation seems to depend on the level of soil water deficiency, hence the reduction of plant water potentials. The results of the second part of the study showed that PGR applications reduced excessive fruit drop. Although all chemical treatments indicated significant effects, a single spray application of N-(2-chloro-4-pyridyl)-N-phenylurea (CPPU) and 1-naphtaleneacetic acid (NAA) effectively improved fruit retention. Furthermore, those spray applications led to a greater fruit set per inflorescennce than irrigation. However, IAA-export was not clearly affected by irrigation or PGR applications. The results of the third part of the study indicate positive effect of irrigation on fruit retention in both cultivars, which might be influenced by increased pedicel thickness thus increased carbon/nutrient availability to the fruit during critical environmental periods. Moreover, shortage of carboydrate supply to the fruit may be associated with a reduction of IAA-export out of the fruit and this in turn triggers the abscission process. In conclusion, this research proved that prevailing environmental conditons, particulary hot, dry winds, induce premature fruit drop in mango in Northern Vietnam. The identification of the physiological basis of premature fruit drop allowed the development of effective crop management strategies (e.g. PGR applications, irrigation) to overcome unfavourable environmental conditions and to reduce or even inhibit plant responses associated with premature fruit drop. The presented results suggest, that setting up an irrigation system increased fruit retention, which; however, is a great investment for farmers. It was shown that the ease of PGR application and the efficiency of the treatment is a promising alternative to irrigation in oder to prevent excessive fruit drop in mango. The development of effective, fruit drop reducing crop management strategies may also optimized crop loads and enhanced financial returns to growers.
Nitrous oxide emissions and mitigation strategies : measurements on an intensively fertilized vegetable cropped loamy soil
(2011) Pfab, Helena; Müller, Torsten
Nitrous oxide (N2O) is a potent greenhouse gas which is also involved in stratospheric ozone depletion. There is consensus that a reduction in N2O emissions is ecologically worthwhile. Agricultural soils are the major source of N2O emissions in Germany. It is known that high N-fertilization stimulates N2O emissions by providing substrate for the microbial production of N2O by nitrification and denitrification in soils. However, outside the vegetation period, winter freeze/thaw events can also lead to high N2O emissions. Winter emissions constitute about 50% of total emissions in Germany. Therefore, annual datasets are a prerequisite for the development of N2O mitigation strategies in regions with winter frost. Many studies have investigated mitigation strategies for N2O emissions from agricultural soils. However, N2O release from vegetable production has seldom been studied. None of the existing trace gas measurements on intensive vegetable production is representative for the climatic conditions of Southern Germany. Due to the high fertilizer N-input (resulting in high levels of mineral N in the soil) and N-rich residues in late autumn, high annual N2O emissions are to be expected. N2O fluxes were measured from a soilcropped with lettuce and cauliflower in Southern Germany by means of the closed chamber method, at least weekly, for two years. An additional study was conducted using 15 N labeled ammonium sulfate nitrate (ASN) fertilizer and exchange of labeled and unlabeled residues to obtain information about the sources (fertilizer, residues, soil internal mineralization) of N2O emissions. Different mitigation strategies such as fertilizer reduction, addition of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) and banded fertilization were evaluated with respect to their reduction potential on an annual base. Fertilizer reduction is supposed to decrease the soil mineral N level, reducing the available substrate for N2O producing microorganisms. DMPP is a chemical compound which inhibits nitrification enzymatically. In banded fertilization, ammonium rich fertilizer is applied in a depot. This high concentration is also supposed to inhibit nitrification as it is toxic to microorganisms. N2O emissions should be firstly reduced directly by this inhibition of nitrification and secondly, by a lower nitrate content in soil resulting in less N2O release due to denitrification. A high temporal variability in N2O fluxes was observed with emission peaks after N-fertilization, after the incorporation of crop residues (especially in combination with N-fertilization), after rewetting of dry soil and after thawing of frozen soil in winter. Total cumulative annual emissions were 8.8 and 4.7 kg N2O-N ha-1 a-1 for the first and second experimental year in the conventionally (broadcast) fertilized treatment. This treatment was fertilized according to the German Target Value System. N2O emission factors were 1.6 and 0.8%. This is within the range of 0.3 - 3% which is cited in the Guidelines for the Calculation of National Greenhouse Gas Inventories proposed by the Intergovernmental Panel of Climate Change (IPCC). A positive correlation was found in both years between the mean nitrate content of the top soil and the cumulative N2O emissions of all treatments (r2=0.44 and 0.68) as well as between the N-surpluses and the cumulative N2O emissions of the different fertilizer levels during the first year (r2=0.95). Fertilizer reduction from fertilization according to good agricultural practice following the recommendations of the German Target Value System reduced annual N2O emissions by 17% in the first experimental year without yield reduction. For the second year, the reducing effect was 10%, but statistically not significant. Another fertilizer reduction of a further 20% reduced N2O emissions, but also resulted in lower lettuce yields in the first year. Therefore, an additional fertilizer reduction is not recommendable. This work provides, for the first time, annual datasets on the effect of DMPP-application on N2O emissions. Addition of DMPP significantly reduced annual N2O emissions by > 40% during both years, there was also a pronounced effect, both during the vegetation period and winter. The reason for the reducing effect in winter is not yet clear because the degradation of the active agent DMPP is temperature dependent and should take about 6 to 8 weeks under summer climatic conditions. However, we still observed significant reductions in N2O emissions in winter, about 3 months after the application. Furthermore, a reduction in CO2 release was observed indicating a possible influence on heterotrophic activities or at least on their C-turnover. Due to its high N2O mitigation potential, further investigations concerning the functional and structural changes in microbial biomass after DMPP application are needed. Banded fertilization with ASN did not result in the expected reduction in N2O emissions on an annual base. Even when exchanging the ASN fertilizer by nitrate-free ammonium sulfate, N2O emissions were not diminished. We assume that the high emissions were derived from the microbially intact surroundings of the depots, where nitrification was not inhibited and nitrate concentrations were probably very high, creating ideal conditions for denitrification. After one year, the major part of the fertilizer-15N was found in the soil. Only between 13 -15% of the fertilizer was taken up by the marketable plant parts. 1.4% of the 15N was lost as N2O-N. Total 15N recovery was 70% after one year. The losses of non-recovered N were probably caused by nitrate leaching or as gaseous compounds such as N2 or NOx. Compared to cereal production systems, the N use efficiency of this vegetable production system is much lower, even with an optimized fertilization strategy. The measurement of 15N abundances in the N2O revealed that the most significant part of the emissions (38%) was derived from the fertilizer-N which had been taken up by cauliflower residues. N2O emissions directly derived from lettuce and cauliflower fertilizer contributed 26% and 20% respectively while N2O emissions from soil internal N pools accounted for 15%. The contribution of lettuce residues was negligible due to their low amount of C and N. The reason for the high importance of the cauliflower residues was ascribed to the temporarily C-limitation of the system and the provision of electron donators by organic material. Furthermore, O2 is consumed during their degradation leading to the formation of anaerobic microsites when soil moisture is high. These sites offer ideal conditions for denitrification. Especially the combination of mineral N-fertilization and input of organic substance was found to increase N2O emissions. Therefore, the influence of a de-synchronization of the incorporation of crop residues and the mineral N-fertilization by waiting periods of up to 3 weeks was tested in an additional field trial during the cultivation of chard. The longer the waiting time between incorporation of crop residues and N-fertilizer application was, the lower were the N2O emissions. However, the effect was not statistically significant on an annual base. In an additional microcosm incubation model study, the effect of reduced and increased input as well as of different C/N-ratios of cauliflower residues was analyzed. It was shown that due to the high nitrate level in the microcosms only the amount of residue input has an effect on the N2O emissions. The N2O emissions increased with increased amount of cauliflower residues. Although the emission factors were within the range given by the IPCC, the absolute annual N2O emission was high in intensive vegetable production due to the high N-input. Further research is required in order to fully understand the effect of DMPP on the processes of N2O production in the field. Our study underlines the importance of avoiding N-surpluses and of strategies for residue management to reduce N2O emissions in intensive vegetable production.
Membrane transport and long-distance translocation of urea in Arabidopsis thaliana
(2011) Bohner, Anne; von Wirén, Nicolaus
Urea is a soil nitrogen (N) form available to plant roots and a secondary N metabolite liberated in plant cells by protein degradation, especially during senescence. Despite the fact that urea also represents the most widespread form in N fertilizers used in agricultural plant production, membrane transporters that might contribute to urea uptake in plant roots or urea retranslocation in senescent leaves have so far been characterized only in heterologous systems. The first part of the thesis investigated a role of the H+/urea cotransporter AtDUR3 in N nutrition of Arabidopsis thaliana plants. T-DNA insertion lines with a defective expression in AtDUR3 showed impaired growth on urea as a sole nitrogen source. In transgenic lines expressing an AtDUR3-promoter-GFP construct, promoter activity was upregulated under N deficiency and localized to the rhizodermis, including root hairs, as well as to the cortex in more basal root zones. The AtDUR3 protein accumulated in plasma membrane-enriched protein fractions, and AtDUR3 gene expression in N-deficient roots was repressed by ammonium and nitrate but induced after supply of urea. Higher urea accumulation in roots of wild-type plants relative to the T-DNA insertion lines confirmed that urea was the transported substrate of AtDUR3. Influx of 15N-labeled urea allowed the calculation of an affinity constant of 4 µM. These results indicated that AtDUR3 is the major transporter for high-affinity urea uptake in Arabidopsis roots and suggested that the high substrate affinity of AtDUR3 reflects an adaptation to the low urea levels usually found in unfertilized soils. A physiological function of urea and its transporters in leaves was investigated in the second part of the thesis. Currently it is unclear whether transport and metabolism of urea might limit the overall retranslocation of N during senescence. AtDUR3 transcript levels were only slightly de-repressed under N starvation, but strongly increased in senescent leaves. Urea concentrations in leaf samples of different plant and leaf age showed a strong increase after plants turned into generative growth. In parallel, mRNA as much as the protein abundance of AtDUR3 increased with leaf age. The analysis of leaf petiole exudates revealed that urea was indeed a translocated N form and urea-N represented approx. 13% of the total amino acid-N irrespective of the N status of the plant. Urea concentrations determined in apoplastic wash fluids supported a role of AtDUR3 in urea retrieval from the leaf apoplast, and transgenic AtDUR3-promoter-GUS lines indicated a localization of AtDUR3 promoter activity in the vasculature of old leaves. Thus, AtDUR3 might keep internal urea in the cytosol by urea retrieval from the apoplast, allowing urea to be transported to the vascular bundle, where it is either passively loaded to the phloem or converted into amino acids for long-distance N translocation. A strong daytime-dependent phenotype with shorter leaf petioles of an Arabidopsis line overexpressing AtDUR3 led to an in silico analysis of the AtDUR3 promoter sequence revealing that salicylic acid (SA) appears to induce AtDUR3 gene expression in senescent leaves. SA is well known for its involvement in the initiation of senescence. A strongly enhanced uptake capacity for 15N-labeled urea in N-sufficient Arabidopsis roots after SA pretreatment indicated that SA might be able to mimic N-deficiency conditions, paving the way to the possibility that SA builds a regulatory link between developmental and N deficiency-induced senescence.
Mixed modelling for phenotypic data from plant breeding
(2011) Möhring, Jens; Piepho, Hans-Peter
Phenotypic selection and genetic studies require an efficient and valid analysis of phenotypic plant breeding data. Therefore, the analysis must take the mating design, the field design and the genetic structure of tested genotypes into account. In Chapter 2 unbalanced multi-environment trials (METs) in maize using a factorial design are analysed. The dataset from 30 years is subdivided in periods of up to three years. Variance component estimates for general and specific combining ability are calculated for each period. While mean grain yield increased with ongoing inter-pool selection, no changes for the mean of dry matter yield or for variance component estimate ratios were found. The continuous preponderance of general combining ability variance allows a hybrid selection based on general combining effects. The analysis of large datasets is often performed in stage-wise fashion by analysing each trial or location separately and estimating adjusted genotype means per trial or location. These means are then submitted to a mixed model to calculate genotype main effects across trials or locations. Chapter 3 studies the influence of stage-wise analysis on genotype main effect estimates for models which take account of the typical genetic structure of genotype effects within plant breeding data. For comparison, the genetic effects were assumed both fixed and random. The performance of several weighting methods for the stage-wise analysis are analysed by correlating the two-stage estimates with results of one-stage analysis and by calculating the mean square error (MSE) between both types of estimate. In case of random genetic effects, the genetic structure is modelled in one of three ways, either by using the numerator relationship matrix, a marker-based kinship matrix or by using crossed and nested genetic effects. It was found that stage-wise analysis results in comparable genotype main effect estimates for all weighting methods and for the assumption of random or fixed genetic effect if the model for analysis is valid. In case of choosing invalid models, e.g., if the missing data pattern is informative, both analyses are invalid and the results can differ. Informative missing data pattern can result from ignoring information either used for selecting the analysed genotypes or for selecting the test environments of genotypes, if not all genotypes are tested in all environments. While correlated information from relatives is rarely directly used for analysis of plant breeding data, it is often used implicitly by the breeder for selection decisions, e.g. by looking at the performance of a genotype and the average performance of the underlying cross. Chapter 4 proposed a model with a joint variance-covariance structure for related genotypes in analysis of diallels. This model is compared to other diallel models based on assumptions regarding the inheritance of several independent genes, i.e. on genetic models with more restrictive assumptions on the relationship between relatives. The proposed diallel model using a joint variance-covariance structure for parents and parental effects in crosses is shown to be a general model subsuming other more specialized diallel models, as these latter models can be obtained from the general model by adding restrictions on the variance-covariance structure. If no a priori information about the genetic model is available the proposed general model can outperform the more restrictive models. Using restrictive models can result in biased variance component estimates, if restrictions are not fulfilled by the data analysed. Chapter 5 evaluates, whether a subdivision of 21 triticale genotypes into heterotic pools is preferable. Subdividing genotypes into heterotic pools implies a factorial mating design between heterotic pools and a diallel mating design within each heterotic pool. For two (or more) heterotic pools the model is extended by assuming a joint variance-covariance structure for parental effects and general combing ability effects within the diallel and within the factorials. It is shown that a model with two heterotic pools has the best model fit. The variance component estimates for the general combing ability decrease within the heterotic pools and increase between heterotic pools. The results in Chapter 2 to 5 show, that an efficient and valid analysis of phenotypic plant breeding data is an essential part of the plant breeding process. The analysis can be performed in one or two stages. The used mixed models recognizing the field and mating design and the genetic structure can be used for answering questions about the genetic variance in cultivar populations under selection and of the number of heterotic pools. The proposed general diallel model using a joint variance-covariance structure between related effects can further be modified for factorials and other mating designs with related genotypes.
Nutritional and climatic effects on berry shrivel of grapevines in Southern Germany
(2012) Bachteler, Kristina; Wünsche, Jens Norbert
Berry shrivel (BS) is one of the economically most important physiological disorders in grapevine, but it is also one of the least studied ones. At the beginning of the ripening process, berries stop accumulating sugars and lose their turgescence. The must weight remains low, the berries taste sour and bitter. During the last ten years, several studies were conducted to narrow eliciting factors. As a result, an unbalanced ratio of K and Mg in the soil was considered likely to induce BS. To verify this hypothesis, two fertilization trials with two different varieties each, one via the soil and one foliar fertilization trial, were initiated. Within two years, no effect on the incidence of BS was evident. In the foliar fertilization trials, Mg, K and Ca fertilizers were tested with their effect on BS. For the first year, no significant differences could be observed. In the second year, more berries were affected by BS in the plots treated with Ca fertilizer. The plots with Mg fertilizer showed significantly less berries affected by BS than the untreated control in one variety. Extensive analysis of concentrations of Ca, Mg and K in berries illustrate that berries affected by BS show significantly higher concentrations of Ca compared to healthy berries. The loss of quality of wines made of berries affected by BS was demonstrated by must and wine analysis as well as by a consumer preference analysis. Phenolic compounds (in particular resveratrol) that are often used as indicators of abiotic stress were analysed as well. It was supposed that BS is caused or increased by abiotic stress so that the concentration of resveratrol in berries affected by BS is increased as well. However, in all varieties analysed, the concentration of resveratrol was higher in healthy berries than in affected ones. A direct connection between weather condition at bloom and especially at ripening was examined. Observations at monitoring sites and reports from other countries seem to show that cool and wet weather at these phenological stages might increase the risk of BS. It was only possible to statistically prove a connection between the precipitation at bloom and the incidence of BS.
Boron foliar fertilization: impacts on absorption and subsequent translocation of foliar applied Boron
(2012) Will, Silke; Müller, Torsten
Foliar fertilization is an agricultural practice to supply plants with a specific nutrient in times of low soil availability of the nutrient or low root activity, e.g. during generative growth. The focus of this study was placed on Boron (B). Boron is an essential micronutrient for higher plants and deficiency appears in many countries on numerous crops throughout the world. B fertilization is often applied as foliar fertilizer, but the efficiency is inconsistent. The possible physiological function of B in plants is described in Chapter 1 within the general introduction. The experiments were conducted on two disparate crop species (soybean and lychee) and the impact of different parameters on foliar B absorption and subsequent translocation was studied. The first study (Chapter 2) shows the impact of plant B status on foliar B absorption and subsequent translocation in soybean. The limited absorption of foliar applied B in B deficient plants was observed in soybean and in lychee. The physiological study was developed for soybean plants pre-treated with different B root supply, ranging from deficient to B intoxicated plants. In addition, different formulations were tested in order to increase the subsequent B translocation after foliar B absorption. For this reason polyols (mannitol, sorbitol) were added to the foliar formulations, as they form stable polyol borate ester with B and these compounds enable phloem mobility in some species. Lowest absorption was observed in plants with B deficiency and B intoxication, whereas the share of subsequent B basi translocation was highest. Results correlated with measurements on stomata opening and water potential. The interruption of the transpiration stream, indicated by high water potentials in B deficient and intoxicated plants, might facilitate B phloem translocation, as it was shown in recent publications. Absorption rates were increased in treatments with polyol supplementation, probably due to a humectants effect (lowering the DRH). Subsequent translocation could not be improved by the addition of polyols. In Chapter 3 the impact of leaf side of application and adjuvant supplementation on foliar B absorption and subsequent translocation was studied on lychee and soybean. The effect of the adjuvants CaCl2 and sorbitol as humectant adjuvants and mannitol and sorbitol as B-binding adjuvants were investigated. Both plant species differed greatly in total absorption rates. Boron absorption through the abaxial leaf side was more than three-fold (soybean) or seven-fold (lychee) higher than through the adaxial side The addition of adjuvants significantly enhanced the rate of B absorption in soybean, but had no effect on B absorption in lychee. The positive results of adjuvant supplementation in soybean might be attributed to the humectants effect. Subsequent translocation could not be increased in neither of the treatments. The results on foliar B absorption via the abaxial leaf surface in both species suggest a high demand for future research, e.g. techniques to spray the abaxial leaf surface. In Chapter 4 the focus was to assess the impact of different parameters on foliar B absorption and subsequent translocation in lychee. B solutions were applied on the adaxial versus the abaxial leaf surface of mature or immature leaves. In addition, nocturnal versus diurnal application was studied. Absorption was significantly increased after application to the abaxial leaf surface. The parameters leaf age and time of application did not affect absorption. Subsequent translocation of foliar absorbed B increased significantly after foliar application of B to mature in comparison to immature leaves. Nocturnal application of B resulted in significantly enhanced basipetal B translocation. The efficacy of foliar B fertilization can be limited in lychee, especially if only the adaxial leaf surface is targeted as it commonly occurs with the spraying techniques available in many lychee orchards. The practical implications of our results clearly show that B foliar sprays should be applied nocturnally to the abaxial leaf surface. In conclusion, absorption and subsequent translocation of foliar applied B can be increased by different parameters in lychee and soybean. Plant B status and leafside of application showed a strong impact on foliar B absorption. All results are discussed in Chapter 5.
Biomass production for bioenergy as an interface between yield optimisation, ecology and human nutrition : a question of resource efficiency
(2012) Gauder, Martin; Claupein, Wilhelm
In this thesis, specific questions dealing with sustainability of bioenergy were analysed on regional scales. One focus was put on food security and the connections to bioenergy production. Therefore a study, based on the comprehensive range of information available, was conducted for ethanol production in Brazil. The second focus laid on Europe and the potentials and environmental risks which come along with bioenergy production. A study on interannual yield performance of long-term Miscanthus plantations was conducted to evaluate potentials and genotype diversities of Miscanthus cropping in Southwest Germany. To identify the possible contribution of by-products from agriculture, a third study dealt with amount and distribution of surplus straw in Southwest Germany. Environmental aspects were addressed in a field trial, which monitored trace gas fluxes from soils under different energy plants also in Southwest Germany. The last study examined the potential of establishing large-scale poplar plantations in Romania and how this could contribute to the regional energy security.
Analysis of the interaction between the helper component proteinase (HC-Pro) of Zucchini yellow mosaic virus (ZYMV) and the plant RNA methyltransferase Hua enhancer 1 (HEN1)
(2012) Jamoos, Rana; Reustle, Götz
The helper component-proteinase (HC-Pro) is a multifunctional protein found among potyviruses. It plays multiple roles in the viral infection cycle and some of these functions have been mapped to different regions of the protein. The subcellular localization of several viral RNA silencing suppressor (RSS) proteins was identified. In this study, we have shown that the Zucchini yellow mosaic virus (ZYMV) HC-Pro wild type (HC-ProFRNK) and its mutant, HC-ProFINK, had a diffuse cytoplasmic localization and formed aggregates along the endoplasmatic reticulum (ER). HC-ProFRNK and HC-ProFINK were stably expressed in N. benthamiana and A. thaliana plants. In addition, the HC-ProFRNK and HC-ProFINK were fused to a nuclear localization signal (NLS) sequence (NLS-HC-ProFRNK and NLS-HC-ProFINK) and these transgenes constructs were also stably transformed into N. benthamiana and A. thaliana. Expression of all four transgenes caused different effects in the two plant species. HC-ProFRNK?producing A. thaliana plants displayed severe phenotypic alterations. In A. thaliana, the HC-ProFINK led to a reduced number of seed set. In N. benthamiana expressing HC-ProFRNK/FINK, generally no or only slight phenotypic changes were monitored. The NLS-HC-ProFRNK/FINK-producing plants displayed clear phenotypes. Flower malformations and severe reduction of seed set were the most conspicuous observations made. In general, more severe developmental disturbances were observed in transgenic A. thaliana than in N. benthamiana plants. ZYMV HC-Pro RSS activity was previously demonstrated in N. benthamiana plants by transient expression experiments. In this study, RSS activity was confirmed in N. benthamiana lines stably expressing ZYMV HC-ProFRNK/FINK. Notably, these plants did not show significant morphological alterations. Because the RSS activity of HC-Pro leads to enhanced transgene expression, our ?symptom-free? transgenic N. benthamiana plants may serve as a platform for over-expression of foreign genes. In tobacco, transient or over-expression of rgs-CaM mimicked the phenotypic effects of Tobacco etch virus (TEV) HC-Pro, indicating that TEV HC-Pro may up-regulate rgs-CaM expression. However, our data revealed no significant difference in the levels of rgs?CaM mRNA in N. benthamiana plants expressing HC-ProFRNK/FINK when compared with the steady-state mRNA level found in the wild type plants. It is likely that RSS proteins from related viruses do not necessarily exhibit identical effects on RNA silencing. In addition, plant species might also differentially respond to identical RSS proteins. The small RNA (sRNA) binding activity of HC-Pro was evident in N. benthamiana plants co-expressing the HC-ProFRNK and an infectious transgene construct of Potato spindle tuber viroid (PSTVd). In comparison to PSTVd-infected N. benthamiana plants, Northern blot analysis showed increase accumulation of viroid-derived sRNAs in the double transformed plants. There is indirect evidence showing that in plants, transient or stable expression of HC-Pro results in decreased accumulation of methylated sRNAs. In this study, we demonstrated that recombinant ZYMV HC-Pro inhibited the methyltransferase activity of the A. thaliana Hua enhancer 1 (AtHEN1) in vitro. Moreover, we found that HC-ProFINK lacking sRNA-binding activity, also inhibited AtHEN1 activity. In contrast, truncated HC-Pro and total soluble bacterial proteins did not affect AtHEN1 activity. Using enzyme-linked immunosorbent assays, we provided evidence that the HC-ProFRNK/FINK, both bound to AtHEN1. Our results strongly indicated that inhibition of the AtHEN1 activity by HC-Pro is probably due to direct interactions between both proteins. We concluded that AtHEN1 inhibition and sRNA-binding activities of HC-Pro are independent of each other. Using the yeast two-hybrid (Y2H) system, we could show that in contrast to RSS proteins from some other viruses, the HC-ProFRNK/FINK proteins did not interact with the Argonaute 1 (AGO1) protein. Similar to previous reports our data confirmed that HC-Pro interacts with itself to form homodimers. Notably, only HC-ProFRNK but not HC-ProFINK was able to interact with itself. The conserved FRNK box is located in the central domain of HC-Pro and this domain has been previously shown to be involved in self-interaction. It should be noted that parts of the work have been published in: - Jamous R. M., Boonrod K., Fuellgrabe M. W., Ali-Shtayeh M. S., Krczal G. and Wassenegger M. (2011). The HC-Pro of the Zucchini Yellow Mosaic Virus (ZYMV) inhibits HEN1 methytransferase activity in vitro. J. Gen. Virol. 92, 2222-2226. - Fuellgrabe M., Boonrod K., Jamous R., Moser M., Shiboleth Y., Krczal G. and Wassenegger M. (2011). Expression, purification and functional characterization of recombinant Zucchini yellow mosaic virus HC-Pro. Protein Expr. Purif. 75: 40-45.
Evaluation of alternative statistical methods for genomic selection for quantitative traits in hybrid maize
(2012) Schulz-Streeck, Torben; Piepho, Hans-Peter
The efficacy of several contending approaches for Genomic selection (GS) were tested using different simulation and empirical maize breeding datasets. Here, GS is viewed as a general approach, incorporating all the different stages from the phenotypic analysis of the raw data to the marker-based prediction of the breeding values. The overall goal of this study was to develop and comparatively evaluate different approaches for accurately predicting genomic breeding values in GS. In particular, the specific objectives were to: (1) Develop different approaches for using information from analyses preceding the marker-based prediction of breeding values for GS. (2) Extend and/or suggest efficient implementations of statistical methods used at the marker-based prediction stage of GS, with a special focus on improving the predictive accuracy of GS in maize breeding. (3) Compare different approaches to reliably evaluate and compare methods for GS. An important step in the analyses preceding the marker-based prediction is the phenotypic analysis stage. One way of combining phenotypic analysis and marker-based prediction into a single stage analysis is presented. However, a stagewise analysis is typically computationally more efficient than a single stage analysis. Several different weighting schemes for minimizing information loss in stagewise analyses are therefore proposed and explored. It is demonstrated that orthogonalizing the adjusted means before submitting them to the next stage is the most efficient way within the set of weighting schemes considered. Furthermore, when using stagewise approaches, it may suffice to omit the marker information until the very last stage, if the marker-by-environment interaction has only a minor influence, as was found to be the case for the datasets considered in this thesis. It is also important to ensure that genotypic and phenotypic data for GS are of sufficiently high-quality. This can be achieved by using appropriate field trial designs and carrying out adequate quality controls to detect and eliminate observations deemed to be outlying based on various diagnostic tools. Moreover, it is shown that pre-selection of markers is less likely to be of high practical relevance to GS in most cases. Furthermore, the use of semivariograms to select models with the greatest strength of support in the data for GS is proposed and explored. It is shown that several different theoretical semivariogram models were all well supported by an example dataset and no single model was selected as being clearly the best. Several methods and extensions of GS methods have been proposed for marker-based prediction in GS. Their predictive accuracies were similar to that of the widely used ridge regression best linear unbiased prediction method (RR-BLUP). It is thus concluded that RR-BLUP, spatial methods, machine learning methods, such as componentwise boosting, and regularized regression methods, such as elastic net and ridge regression, have comparable performance and can therefore all be routinely used for GS for quantitative traits in maize breeding. Accounting for environment-specific or population-specific marker effects had only minor influence on predictive accuracy contrary to findings of several other studies. However, accuracy varied markedly among populations, with some populations showing surprisingly very low levels of accuracy. Combining different populations prior to marker-based prediction improved prediction accuracy compared to doing separate population-specific analyses. Moreover, polygenetic effects can be added to the RR-BLUP model to capture genetic variance not captured by the markers. However, doing so yielded minor improvements, especially for high marker densities. To relax the assumption of homogenous variance of markers, the RR-BLUP method was extended to accommodate heterogeneous marker variances but this had negligible influence on the predictive accuracy of GS for a simulated dataset. The widely used information-theoretic model selection criterion, namely the Akaike information criterion (AIC), ranked models in terms of their predictive accuracies similar to cross-validation in the majority of cases. But further tests would be required to definitively determine whether the computationally more demanding cross-validation may be substituted with the more efficient model selection criteria, such as AIC, without much loss of accuracy. Overall, a stagewise analysis, in which the markers are omitted until at the very last stage, is recommended for GS for the tested datasets. The particular method used for marker-based prediction from the set of those currently in use is of minor importance. Hence, the widely used and thoroughly tested RR-BLUP method would seem adequate for GS for most practical purposes, because it is easy to implement using widely available software packages for mixed models and it is computationally efficient.
Lentil production in Germany : testing different mixed cropping systems, sowing dates and weed controls
(2012) Wang, Lina; Claupein, Wilhelm
As a kind of legume crop, lentils (Lens culinaris Medik.) with their high nutritional value are grown mainly for human consumption in many regions of the world. The crop has benefits in crop rotation due to its symbiotic N-fixation, which is important especially in organic farming, and it can also increase crop biodiversity in arable land. In Europe, lentils are considered one of the popular leguminous food crops. However, the cultivation and scientific research on lentils were neglected in Germany and Central Europe over the past 50 years. Recently, farmers have begun to realize the value of lentils and have re-introduced the crop into organic and conventional farming in Central Europe. The lentil plant has a weak stalk and is easily lodging. Lodging plants cannot be completely cut and picked up by combine harvesters, and result in yield loss, especially under the wet conditions that often occur in Central Europe. To avoid lodging of crop, lentils were commonly grown in mixed cropping with cereals, such as oat (Avena sativa L.), barley (Hordeum vulgare L.) and rye (Secale cereale L.). However, there is little current information on lentil cultivation under temperate climates in this region. One of the most relevant challenges for growing lentil is how to explore its yield potential adapt to the local conditions. Moreover, lentil plant has a low competition capacity against weeds which are always one of the big agronomic problems especially on organic farm. Therefore, three field experiments presented in this dissertation were carried out to design and improve lentil cropping systems under organic farming in Germany in terms of productivity and competitiveness performance, suitable species and proportion of companion crops, lentil cultivars, sowing dates, weed control, and seed quality. The results should be used to adapt lentil cropping systems to different local climatic conditions in Germany. The specific objectives were (i) to optimize lentil-based mixed cropping systems through different combinations of companion crops (barley, wheat (Triticum aestivum L.), oat, linseed (Linum usitatissimum L.) and buckwheat (Fagopyrum esculentum Moench)) and mixing ratios, which were expected to show different performance on crop productivity, weed infestation, and lentil lodging, (ii) to determine whether different sowing time (early, medium, late) have effects on a standard lentil-barley mixed cropping system in regard to crop yield and weed control, (iii) to test whether woodchip mulch can help suppressing weeds and increasing crop yield in lentil monocropping and mixed cropping, (iv) to determine whether different mixing ratios affect seed protein content in lentil-cereals (barley, wheat) mixed cropping system. To achieve the first objective, a two-year field experiment of mixed cropping of lentils with five spring-sown companion crops: naked-barley, wheat, oats, linseed and buckwheat was conducted at the organic research station Kleinhohenheim in 2009 and 2010. Besides sole lentil and sole companion crops, three mixing ratios (3:1, 1:1, 1:3) were used. Lentil grain yield was 1.47 t ha-1 in monocropping and 0.58-1.07 t ha-1 in mixed cropping, depending on the mixing ratio and companion crop (Chapter 2). The land equivalent ratio (LER) was higher in mixed cropping than in monocropping generally. Lentil-wheat and lentil-barley mixed cropping with a ratio of 3:1 resulted in the highest LER (ca. 1.50) whereas lentil-linseed had the lowest LER in all ratios. Lowest lodging was observed in lentil-wheat and lentil-oat mixed cropping. Additionally, mixed cropping with ratios of 3:1, 1:1 and 1:3 (lentil: companion crop) reduced weed biomass by 29 %, 41 % and 24 %, respectively, compared with lentil monocropping. The results indicated that lentil mixed cropping in the study seemed more promising than monocropping under the given conditions of the location. Except for the linseed, all tested species can be well used as companion crops especially the two cereals (barley and wheat) which can be recommended. The mixing ratio should consider the total yield advantage (LER), the risk of crop lodging, and marketing considerations of both crops. To achieve the second objective of the study, another two-year (2009-2010) field trial was carried out at two sites: the organic research station Kleinhohenheim (KH) and the conventional research station Oberer Lindenhof (OLI) (Chapter 3). The crop was sown at three dates (early, medium and late) in the period from March to May. Four genotypes of lentil: Anicia, Schwarze Linse, Hellerlinse and Berglinse were mixed-cropped with naked-barley at a ratio of 3:1 (lentil:barley) at each sowing date. Results showed that grain yield of crops was significantly higher at the earliest sowing both for lentils (3.0 t ha-1 at KH, 2.4 t ha-1 at OLI) and barley (1.2 t ha-1 at KH, 2.6 t ha-1 at OLI). Lentil seed per plant, barley seed per ear, and thousand kernel weight of crops decreased significantly with delayed sowing. At KH experimental site, weed biomass increased significantly with delayed sowing and was independent of the lentil genotype, whereas sowing date had no significant effect on overall weed biomass production at OLI. The results indicated that early sowing can increase the yield of lentils, and can also be used as an indirect method of weed control in organic farming. To further control weeds to achieve the third objective, a field experiment of applying woodchips mulch on lentils was carried out at the organic research station Kleinhohenheim, in the years 2009 and 2010 (Chapter 4). Two years on average, an amount of 160 m3 ha-1 (fresh matter) woodchips mulch reduced weed biomass and weed density in both cropping systems compared to no mulch treatment, with a reduction by 43 % and 29 % (sole), and by 51 % and 30 % (mixed) respectively. Mixed cropping of lentils with barley (3:1) also decreased weed biomass compared with lentil sole cropping; however, no effect on weed density was observed. Lentil grain yield from sole and mixed cropping was 3.0-3.4 t ha-1 and 2.1-2.2 t ha-1 (2009), and 1.0-1.1 t ha-1 and 0.8-0.9 t ha-1 (2010). Barley grain yield was 1.4 t ha-1 in 2009 and 0.7 t ha-1 in 2010. Despite decreasing weeds, the mulch did not improve crops grain yields in mixed or sole cropping. The combination of woodchip mulch and mixed cropping is useful to reduce weed infestation in cropping systems where chemical or mechanical weed control is not possible and for crops with a low capacity for competition against weeds. Another focus of the study was on seed quality (protein content), especially for the cereals (Chapter 5). The two mixed cropping systems: lentil-wheat and lentil-barley with five seeding ratios (4:0, 3:1, 1:1, 1:3, 0:4) were tested at the organic research station Kleinhohenheim in 2009 and 2010 (originated from the experiment 1). Results showed that cereal grain protein increased significantly when their proportion was reduced in the mixture with lentils. Wheat crude protein increased from 10.3 % (2009) and 11.0 % (2010) in monocropping to 11.5 % (2009) and 15.1 % (2010) in mixed cropping with 75 % lentils. Barley crude protein increased in the same way from 13.7 % in monocropping to 15.8 % in mixed cropping with 75 % lentils. However, lentil protein content did not differ significantly across all mixing ratios. Total crude protein in a mixture was significantly higher than that in cereals or lentils monocropping. Mixed cropping with lentils can thus be an option to obtain a high protein content of wheat which is important for a suitable breadmaking quality, particularly in organic farming. Summarizing, the overall results of the study will open new options for growing lentils in Central Europe from where the crop has vanished over the last decades and may guide the future of lentil production in multi-cropping.
The effect of picking time and postharvest treatments on fruit quality of mango (Mangifera indica L.)
(2012) Vu, Hai Thanh; Wünsche, Jens Norbert
Mango production in Northern Vietnam is mainly in the upland areas. The two locally grown cultivars are ?Tron? and ?Hoi? with limited yearly production due to poor traditional crop management practices by ethnic minorities. Both cultivars possess excellent fruit aroma and taste properties, yet there is a need to further improve fresh fruit quality to meet high domestic demand and consumer expectations in the market place, thereby exploiting more products of preferred quality. Assessment of quality parameter and consumer preference can assist to precisely determine optimum harvest time and suitable storage regime for a given cultivar. Furthermore, specific postharvest treatments such as applications of hot water, 1-MCP or ethrel for manipulating fruit ripening and shelf-life may help to enhance economic returns and thus to make mango production in the long term more profitable. The research work on both cultivars was carried out on farmer orchards near the township of Yen Chau, Son La Province, Vietnam, in 2007, 2008 and 2009. The research objectives were to (1) monitor internal and external fruit quality changes in relation to varying select picks throughout the harvest period and to a range of storage temperatures; (2) investigate the effect of 1-MCP on various fruit ripening parameters for maintaining fruit quality and extending shelf-life; (3) evaluate applications of aqueous ethrel solution in cool storage for accelerating fruit ripening; and (4) assess the responses of several external fruit criteria to hot water treatments and subsequent cool storage. At each select pick, fruit was immediately taken to the laboratories at Hanoi University of Agriculture for fruit quality assessment at harvest, and following various postharvest treatments, ex-store. Chemical analyses of fruit tissue samples were performed at the University of Hohenheim. Various physicochemical quality parameters such as fruit weight, skin disorder, skin and flesh colour, flesh firmness, total soluble solids concentration, titrable acidity, as well as concentrations of soluble sugars, starch, vitamin C and carotenoids were evaluated. The results of the first part indicated that key quality criteria for determining the optimal harvest time of ?Tron? and ?Hoi? were determined. ?Hoi? fruit was at best quality when harvested late, preferably in the 2nd or 3rd pick, whereas 1st pick fruit was relatively immature with less than 8% total soluble solid concentration and did not properly ripen when stored at 12ºC. In contrast, ?Tron? fruit should be picked early in the harvest period since the 3rd pick with tree-ripened fruit was only suitable for direct local marketing without storage time. The results also indicated that ?Tron? fruit of the 1st and 2nd pick and ?Hoi? fruit of 2nd and 3rd pick continued the ripening process to full maturity when stored at 12ºC. Consequently, fruit from these picks were suitable for distant markets when handled within 5-10 days at 20ºC or up to 20 days at 12ºC. Generally, ?Hoi? had a greater postharvest potential than ?Tron? but ex-store fruit quality of both cultivars was best with flesh firmness ranging from 70.5 to 96.1 N, skin hue angle from 71.4º to 85.4º, flesh hue angle from 70.1º to 78.5º and total soluble solid concentration from 16.8 to 19.6%. The results of the second part clearly showed that 1-MCP is a useful tool to delay fruit ripening and in particular softening of both cultivars during the postharvest period. Both cultivars treated with 1000 nL?L-1 1-MCP delayed considerably the decrease in TA, skin and flesh hue angle as well as the loss of flesh firmness in the 1st and 2nd pick for about 10 days of storage at 12ºC compared to control. Both cultivars were more sensitive to 1-MCP applications in 1st rather than the 2nd pick. In addition, 1-MCP applications were more effective on ?Tron? fruit than ?Hoi? fruit. The results of the third part indicate that 0.8% ethrel accelerated fruit ripening on fruit from the 1st pick of both cultivars while stored at 12ºC. Ex-store fruit quality was acceptable and met consumer preference. The efficacy of ethrel application on ?Hoi? fruit was greater than that on ?Tron? fruit. The results of the fourth part showed that the degree of skin disorder was considerably decreased when ?Tron? and ?Hoi? fruit were treated with either 48ºC or 50ºC water for 6 min and stored at 12ºC. This treatment delayed skin colour development of ?Hoi? when compared to other treatments. In conclusion, this study demonstrates that lack of proper whole chain fruit quality management systems is the key factor for the limited production of mangoes in Northern Vietnam. Improved fruit quality management can result in more consistent and higher quality particularly for distant markets. Based on the results of this work, ?Tron? and ?Hoi? fruit should be harvested using well-defined and recommended harvest quality indices and thereafter undergo appropriate postharvest management systems to attain higher fruit quality. This will help farmers to better manipulate fruit ripening processes, to deliver high quality fruit to the market and to achieve greater returns and thus livelihoods.
Removal of organic and inorganic pollutants from aqueous solutions by organically modified clayey sediments
(2012) Mubarak, Dalia Mohamed Fahmy; Müller, Torsten
Re-use of agricultural drainage water and industrial wastewater is one of the adopted strategies in different countries to close the gap between water resources and water demands. Drainage and industrial wastewater contain varieties of toxic pollutants that can potentially cause hazard on humans and environment. Although adsorption techniques are considered one of the proper methods for the wastewater treatments, economic aspect is a crucial factor for the broad application of such technique. Addressing this, the thesis concerns on proposing sorbents having the potential to remove heterogeneous pollutants simultaneously, particularly taken in consideration the limited resources in developing and emerging countries, in this study exemplified for Egypt. For this purpose, natural clayey sediments as cheap and environmentally friendly materials were used in combination with various organic modifiers to produce of organically modified clayey sediments (OMCs). In contrast to the natural clayey sediments, OMCs are expected to have the ability to remove heterogeneous pollutants including anionic and cationic as well as organic and inorganic pollutants. The sorbability and desorbability characteristics of OMCs were investigated for Cd2+ and Pb2+ (cationic ), Cr2O72- (anionic-) and metalaxyl m (MM; organic-pollutants). The basic clay materials in OMCs were naturally occurring kaolinitic (kao sediment) and bentonitic (bent sediment) clayey sediments distributed widely in Egypt. Different concentrations of the organic modifiers L-Carnitine (Carnitin), L Cystine dimethyl ester (Cys_ester), Methyltriphenyl-phosphonium (MTP) or Hexadecyltrimethyl-ammonium (HDTM) were employed. The modification of natural clayey sediments with organic modifiers increased the organic carbon contents of OMCs following the order Carnitin < Cys_ester < MTP < HDTM. OMCs based on bent sediments had a higher loading of the organic modifiers than those based on kao sediments and the loading increased with increasing the used concentrations of the organic modifiers. To characterize and confirm the modification of OMCs, the prepared materials were analyzed by mid infrared spectroscopy (MIRS). The obtained spectra showed shifting of the vibration bands of the natural clayey sediments, and depicted the characteristic vibrations bands of the organic modifiers, indicating the interaction between the natural clayey sediments with the organic modifiers and the successful loading. Further analysis by X ray diffraction showed that the modification of OMCs based bent sediments with MTP or HDTM caused an expansion of the interlayer spacing of the clay from 14.5 Å to 17.1 or 19.7 Å, respectively; reflecting a bilayer or pseudo-trimolecular arrangements of MTP or HDTM, respectively, in the clays interlayer. The loading ratios of the organic modifiers on OMCs as a percentage of the CEC of the natural clayey sediments were also calculated. Following the characterization of OMCs, screening experiments were conducted to select the suitable concentration of each organic modifier to be loaded in order to achieve the highest removal of heavy metals. The results showed that loading of OMCs based on kao sediments by HDTM and Carnitin at concentrations equal to or higher than 71and 8 % of the CEC of the natural kao sediment, respectively, caused no relevant differences in the sorption of Cd2+ and Pb2+ compared to natural kao sediment. However, the loading of Cys_ester and MTP at concentrations equal to 38 and 21 % of the CEC or higher increased the sorption of those metal ions. Remarkable enhancements in the sorption of Cr2O72- were obtained by the modification of OMCs based kao sediments with HDTM and Cys_ester. The outcome from these screening experiments with OMCs based bent sediments can be concluded as follow: HDTM and MTP at loading concentrations > 50 % of the CEC of the natural bent sediments were able to remove all Cd2+ and Pb2+ from the solutions. However, increasing the loading concentration of Cys_ester decreased the sorption of those metal ions as compared to natural bent sediment. OMC modified with Carnitin at loading concentration up to 21 % of the CEC was able to remove 84 % of Cd2+ and 100 % of Pb2+ from the solutions but a further increase of Carnitin loading decreased the sorption of the metal ions. The OMCs modified with HDTM and Cys_ester were very efficient in removing Cr2O72- from the solutions and the removal increased with increasing loading concentrations of the organic modifiers. The OMCs based on bent sediments loaded with HDTM, MTP, Carnitin and Cys_ester at loading concentrations equal to 102, 79, 18 and 66 % of CEC of the natural bent sediments, respectively, and in addition OMC loaded with Humic acid (HA), were selected as promising sorbents to test the sorbability and desorbability of OMCs with respect to the pollutants. The sorption processes were investigated as function of the metal concentration, sorption time, the initial solution pH and the electrolyte concentration. OMCs modified with HDTM, MTP, HA and Carnitin showed high sorbability for Cd2+ and Pb2+. However, OMCs modified with Cys_ester displayed the best sorbent for Cr2O72-. OMCs were successful to remove almost all Cd2+, Pb2+ from the solutions at wide ranges of pH; 4-8 and 4-6, respectively, while the optimum for the sorption of Cr2O72- was pH 4. The Langmuir model described adequately the observed sorption data of Cd2+ and Pb2+ on all sorbents and Cr2O72- on OMC modified with Cys_ester better than the Freundlich model. The sorption followed the pseudo second order kinetics with the rate constants demonstrating faster sorption on OMCs with Carnitin and HA for Cd2+ and Pb2+ and faster sorption on OMCs with MTP and Cys_ester for Cr2O72-. Sorption of Cd2+ and Pb2+, particularly on OMCs with Carnitin and HA, were decreased with increasing electrolyte concentrations. Whereas, increasing the electrolyte concentrations enhanced the sorption of Cr2O72- to OMC with Cys_ester. OMCs showed ability to release the sorbed heavy metals, which shows the potential for re-using. The presence of other solutes in the binary and ternary component systems strengthened the sorption of Cr2O72- on OMCs based bent sediments with HDTM and MTP and enhanced the sorption of MM on OMCs with Cys_ester and MTP. Competition phenomena were recorded for the sorption of Cd2+ and MM on OMC with HDTM. No competition behaviours were observed in the sorption of the tested pollutants on OMC with Cys_ester. OMCs with HDTM, MTP and Cys_ester were able to remove Cd2+, Cr2O72- and MM simultaneously from the binary and ternary component systems. The results indicate the prospective application of the OMCs in the treatments of natural agricultural drainage water and industrial wastewater.
Identifizierung und Quantifizierung von Trockenstressreaktionen an ausgewählten Zierpflanzenkulturen
(2013) Krato, Theresa; Wünsche, Jens Norbert
The present thesis gives attention to the development of a practicable screening process for the identification of drought-stress tolerant ornamental plants. Requirements are to be created in terms of reduced water use, market expansion to warmer regions and increased ability of transportation. The studies were included into a cooperative research project involving 4 plant breeding companies, research centre Jülich, research institute Geisenheim and the GFP. Scope of the thesis was the deployment and evaluation of an assessment scheme to quantify drought-stress reactions, the development of dehydration experiments under stationary climatic conditions and to search for physiological markers of drought-stress tolerance. The experiments were mainly conducted on Petunia Cultivars and Impatiens Neu Guinea Grp. Genotypes. Main results of the investigation are listed below: 1. The species specific assessment schemes are based on an accurate visual characterization of the wilting process. The wilting is rated using ranks from 1 ? 9. Assessed parameters were the phyllotaxy, surface texture and leaf color. The assessment schemes were proved to be acceptably objective and precise during the experiments and the genotypes were evaluated accordingly. 2. The plants were dried out under standardized conditions in climate chambers. The decrease of water as well as the occurrence of wilting was recorded. Climatic conditions (temperature, humidity and radiation) in dehydration experiments were set up to reach a rank of 9 in 5 to 9 days according to drought-stress tolerance and pretreatment of genotypes. For this reason, an adequate differentiation between genotypes was ensured even with a single assessment per day. However, the system weight (substrate and plant), which was used to characterize the stress intensity has to be corrected about the fresh weight of plants. The investigated genotypes of Impatiens behaved similarly regarding to their drought-stress tolerance in many replications and consequently allowed for a ranking. In contrast, the ranking order of investigated genotypes of Petunia was vague in experimental replications. However, an influence of water supply on the wilting behavior of plants was detected in this context. 3. In order to search for physiological markers of drought-stress tolerance, studies on water potential, gas exchange and thermal imaging were conducted in line with the dehydrogenation experiments. A tendency was shown, that drought-stress tolerant genotypes reacted later and less distinctive on drying of the substrate compared to susceptible plants. But a correlation between water potential of shoots and water supply in the substrate as well as a differentiation between genotypes was certainly week. This was mainly due to high variation of data. The transpiration rate of investigated plants reacted more on water supply though. The ranking, which was based on the parameter transpiration rate correlated well with the ranking of the wilting behavior from the dehydrogenation experiments. Consequently, the stomata management appears to be a promising indicator of drought-stress tolerance. Thermal imaging showed an increase of leaf temperature with decreasing moisture content of the substrate. Accordingly, the leaf temperature of Impatiens can serve as an indicator for the opening rate of stomata. 4. Currently, the dehydrogenation experiments can be considered as the easiest and most practicable approach to identify drought-stress tolerant genotypes of Impatiens and Petunia due to the results of the present thesis. Physiological measurements supported the ranking of genotypes, which was developed according to the dehydrogenation experiments. Especially, data on the opening rate of stomata illustrated differences between the tested genotypes. However, the dehydrogenation experiment does not provide information of the dependence of vegetative and generative performance of plants on water supply, which is very important for producers of ornamentals. 5. The ranking of drought-stress tolerance from climatic chambers corresponds only partly with results of experiments under field conditions. Therefore, a screening concept has to be developed in a subsequent project to investigate the complex context of climate-stress tolerance.
Feasibility of microbial biodiesel and carotenoid production considering the potential of food processing wastewaters as low cost carbon sources using the example of red yeast Rhodotorula glutinis
(2013) Braunwald, Teresa; Claupein, Wilhelm
Due to the increasing demand for sustainable biofuels, microbial oils as feedstock for the transesterification into biodiesel have gained scientific and commercial interest. Also microbial carotenoids have a considerable market potential as natural colorants. Against this background this thesis assessed the feasibility of biodiesel produced by heterotrophic microorganisms, particularly yeasts, using the example of oleaginous red yeast Rhodotorula glutinis. To improve the economic efficiency of this process, several studies have been conducted in order to test (i) whether wastewaters from the agricultural processing industry can be utilized as low-cost carbon and nutrient source for growth and lipid production by R. glutinis and (ii) if they also facilitate the simultaneous production of beta-carotene and other carotenoids as high-value by-products. It has been shown at a small scale, that agricultural processing wastewaters can be used as feedstock for the microbial production of lipids and carotenoids. The general discussion continues to assess the approach of microbial biodiesel production in a broader context in terms of its economic, environmental and energetic performance. The calculated break-even price of microbial oil, excluding the cost of the carbon source for fermentation, is around double the price of conventional plant oils as competing products. To reduce the costs, cultivation in open raceway ponds was proposed, which led to a cost reduction of around 20 %. In order to assess the potential environmental benefits different life cycle assessments from algae biodiesel production, which share common features with the proposed process, have been analyzed. It was concluded, that microbial biodiesel cannot outperform common 1st generation biodiesel in terms of GHG emissions, whereas factors of eutrophication potential and land competition could be significantly improved. The high climate relevant emissions were mainly driven by the high energy requirements connected to the extraction of microbial oil, which also puts a heavy burden on the energetic efficiency of the process. Considering the potential of continued research and technical development along with the political commitment to promote 2nd and 3rd generation biofuels, it was concluded, that in the long term microbial biodiesel could become a commercial reality above laboratory and pilot scale. Due to the different restrictions this will probably not happen within the next 20-30 years. Contrary to biodiesel, carotenoids are high-value products, with beta-carotene yielding around US$ 600 per kg. Sustained by this high price and allowing for certain improvements regarding beta-carotene yields and extraction techniques, it can be possible to economically and sustainable produce beta-carotene from R. glutinis in the near future.
Sustainable bioenergy cropping concepts : optimizing biomass provision for different conversion routes
(2014) Mast, Benjamin; Claupein, Wilhelm
Today energy from biomass already contributes to a considerable share to the global energy consumption. In particular, certain modern bioenergy streams like biogas, biofuels for transportation etc., are of increasing relevance. However, several of the beneficial aspects, which were initially attributed to the utilization of today’s bioenergy, had to be relativized and the controversies regarding environmental and socio-economic drawbacks have, in the meanwhile, been on the rise. Alongside a shift to advanced conversion technologies, the improvement of bioenergy cropping systems towards a sustainable biomass provision is a key element of future bioenergy production. Against this background, the present thesis assessed various aspects in terms of biomass production, biomass provision and biomass conversion mainly addressing the two bioenergy streams – 2nd generation biofuels and biogas. For biogas, the thesis addresses aspects regarding the development of alternative cropping systems, the evaluation of novel crops for biogas purpose, and the assessment of regional biogas potentials using a crop growth model. The second focus of the thesis was set on biofuels while special attention was given to the production of microbial biodiesel, and the characterization and evaluation of potential feedstocks for this purpose.
Lockerbeerigkeit bei Klonen von Spätburgunder (Pinot noir) : Analyse von molekularen Markern und der Einfluss von Gibberellin auf die Traubenmorphologie
(2014) Hoffmann, Petra; Blaich, Rolf
In viticulture, the architecture of the grape cluster affects the quality of the grapes. Compact grape clusters are more prone to B. cinerea infection, which reduces yield (Vail et al. 1998, Vail et al. 1991). Loose clusters have longer pedicel and rachis structures (Alleweldt 1959) and are less susceptible to B. cinerea. For this reason, the cultivation of clones with the loose cluster trait is of great interest. Loose clusters can result from the application of phytohormones, the spacing of the flower clusters, the thinning of fruit, or a reduced pruning. These treatments reduce berry set and promote pedicle elongation when applied to clones with compact clusters (Alleweldt 1959). Genetically based loose clustered grape phenotypes occur among grapevine cultivars. In this study we are able to differentitate between losse and compact clones using the marker FlExp2 on the basis of sequence data. The loose cluster clones show a 4 bp deletion at 219-222 bp and a C/T transition at 231 bp, unlike the compact cluster clones. In all tested Pinot ssp. clones, the sequence correlated to the phenotype. The marker was tested on other varieties such as Riesling, Gewurztraminer, Chardonnay, Chenin blanc, Cardinal and White Chasselas. The phenotypes were again consistent with the sequence. In the case of loose clustered table grapes, a deletion occurs instead of the transition at 231 bp. Additionally, the variety White Gutedel demonst- rated a C/T transition at 217 bp. These results were confirmed by sequencing 30 clo- nes (loose and compact clusters) in two repetitions in both directions. Both markers shwoed two fragments with a four bp difference. The amplification products are a In- del/SNP mutation for loose cluster and a „CTTT“ mutation for copmact cluster grapes.The CAPS and the SCAR marker identified that the trait of bunch architecture is heterozygous. The sequence of the amplification products was distinct for loose and compact cluster types. The SCAR marker shows two amplification products at 162 bp and 166 bp and the CAPS marker at 283 bp and 287 bp. The heterozygosity didn ́t produce a molecular marker for the MAS. In silico, analysis shows that the identified locus is in the Exon in the Vlexp1 gene. This gene is an expansin gene which is responsible for cell elongation (McQueen- Mason 1992). A part of the role which the hormones play in grape Morphology was analyzed in this study. The inflorescences of the genetically loose clustered clone 1-84 Gm did not show increased gibberellin concentration, indicating that gibberellin does not have a influence on the genetic based loose clone (1-84 Gm). However, the auxin concentra- tion in inflorescences of loose cluster clones increases earlier and remains high lon- ger than in those of the compact cluster clone 18 Gm. After a treatment with gib- berellin, the clone 1-84 Gm exhibited increased concentration of both gibberellin and auxin and formed even looser clusters. Similarly, the same treatment applied to the compact clone 18 Gm resulted in looser clusters and increased concentration of gib- berellin and auxin with a higher concentration of auxin for a longer period of time. It remains unclear precisely how the gibberellin treatment induces looser clusters. It may be that there is an interaction between gibberellin and auxin or that the auxin alone causes the cell extension. It remains an open question whether expansin toge- ther with gibberellin or auxin is responsible for the development of loose clusters, or if it is caused by a gibberellin auxin interaction. The growth pattern of the stalks and inflorescences were identified in order to put these results in context with the results of the hormone and genetic analysis. The stalks and inflorescences of the treated and untreated clones were measured weekly before GA3-application and continued four weeks after application. The growth of the flower clusters ended three weeks af- ter anthesis while the stalks grew continuously. In the loose cluster clone 1-84 Gm, the growth of stalks and flower clusters was significantly larger than in the compact cluster clone 18 Gm. The growth behavior of the peclone 18 Gm when treated with gibberellin was identical to the clone 1-84 Gm without gibberellin treatment. Gib- berellin treatment caused a significant increase in the growth of the stalk and flower clusters. The treated loose cluster clones formed the largest stalks while the untrea- ted compact cluster clone 18 Gm the smallest. Such clone growth behavior results in loose cluster architecture.

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