Graefea J.,Leibniz Institute of Vegetable and Ornamental Crops
Acta Horticulturae | Year: 2017
In Germany, asparagus is usually grown in soil ridges covered by different kinds of plastic. The major objective is the stretching of the harvest season, with a combined use of early cultivars and warming plastic cover types and the use late-sprouting cultivars together with cooling plastics. Secondary objectives are a good quality of spears and short-term control of asparagus yield. Meanwhile, several cover types are used, which consist of one to three layers of plastic. Depending on the current objectives of the grower, he has to choose one cover type. Currently, this decision is based largely on soil temperature, which is measured on farm or provided by central monitoring services over the internet. But cover management would be sounder if the grower knew future soil temperatures in advance below the most important covers. Therefore, we developed a physical model that is able to predict soil temperature below black and white plastics, and mini-tunnels covering black plastics. New solutions were derived for an approximated 2D soil heat transfer, the radiation exchange between the covers and convective heat exchange between the mini-tunnel and the lower plastic. A 5-year validation period showed even better performance than a previously developed more complex model, which was based on 2DSOIL. The proposed model only requires hourly weather data, optical properties of each plastic layer and basic soil properties such as contents of sand, clay and humus. The developed simulation model is currently operational for six sites located in three German Federal States, Brandenburg, Rhineland-Palatinate and Bavaria.
Lueck E.,University of Potsdam |
Ruehlmann J.,Leibniz Institute of Vegetable and Ornamental Crops
Geoderma | Year: 2013
GEOPHILUS ELECTRICUS (nickname GEOPHILUS) is a novel system for mapping the complex electrical bulk resistivity of soils. Rolling electrodes simultaneously measure amplitude and phase data at frequencies ranging from 1. mHz to 1. kHz. The sensor's design and technical specifications allow for measuring these parameters at five depths of up to ca. 1.5. m. Data inversion techniques can be employed to determine resistivity models instead of apparent values and to image soil layers and their geometry with depth. When used in combination with a global positioning system (GPS) and a suitable cross-country vehicle, it is possible to map about 100. ha/day (assuming 1 data point is recorded per second and the line spacing is 18. m). The applicability of the GEOPHILUS system has been demonstrated on several sites, where soils show variations in texture, stratification, and thus electrical characteristics. The data quality has been studied by comparison with 'static' electrodes, by repeated measurements, and by comparison with other mobile conductivity mapping devices (VERIS3100 and EM38). The high quality of the conductivity data produced by the GEOPHILUS system is evident and demonstrated by the overall consistency of the individual maps, and in the clear stratification also confirmed by independent data.The GEOPHILUS system measures complex values of electrical resistivity in terms of amplitude and phase. Whereas electrical conductivity data (amplitude) are well established in soil science, the interpretation of phase data is a topic of current research. Whether phase data are able to provide additional information depends on the site-specific settings. Here, we present examples, where phase data provide complementary information on man-made structures such as metal pipes and soil compaction. © 2013 Elsevier B.V..
Wimmelbacher M.,Friedrich - Alexander - University, Erlangen - Nuremberg |
Bornke F.,Leibniz Institute of Vegetable and Ornamental Crops |
Bornke F.,University of Potsdam
Journal of Experimental Botany | Year: 2014
Redox modulation of protein activity by thioredoxins (TRXs) plays a key role in cellular regulation. Thioredoxin z (TRX z) and its interaction partner fructokinase-like protein 1 (FLN1) represent subunits of the plastid-encoded RNA polymerase (PEP), suggesting a role of both proteins in redox regulation of chloroplast gene expression. Loss of TRX z or FLN1 expression generates a PEP-deficient phenotype and renders the plants incapable to grow autotrophically. This study shows that PEP function in trx z and fln1 plants can be restored by complementation with redox-inactive TRX z C106S and FLN1 C105/106A protein variants, respectively. The complemented plants showed wild-type levels of chloroplast gene expression and were restored in photosynthetic capacity, indicating that redox regulation of PEP through TRX z/FLN1 per se is not essential for autotrophic growth. Promoter-reporter gene studies indicate that TRX z and FLN1 are expressed during early phases of leaf development while expression ceases at maturation. Taken together, our data support a model in which TRX z and FLN1 are essential structural components of the PEP complex and their redox activity might only play a role in the fine tuning of PEP function. © 2014 The Author.
Erlacher A.,University of Graz |
Cardinale M.,University of Graz |
Grosch R.,Leibniz Institute of Vegetable and Ornamental Crops |
Grube M.,University of Graz |
Berg G.,University of Graz
Frontiers in Microbiology | Year: 2014
Lettuce belongs to the most commonly raw eaten food worldwide and its microbiome plays an important role for both human and plant health. Yet, little is known about the impact of potentially occurring pathogens and beneficial inoculants of the indigenous microorganisms associated with lettuce. To address this question we studied the impact of the phytopathogenic fungus Rhizoctonia solani and the biological control agent Bacillus amyloliquefaciens FZB42 on the indigenous rhizosphere and phyllosphere community of greenhouse-grown lettuce at two plant stages. The rhizosphere and phyllosphere gammaproteobacterial microbiomes of lettuce plants showed clear differences in their overall and core microbiome composition as well as in corresponding diversity indices. The rhizosphere was dominated by Xanthomonadaceae (48%) and Pseudomonadaceae (37%) with Rhodanobacter, Pseudoxanthomonas, Dokdonella, Luteimonas, Steroidobacter, Thermomonas as core inhabitants, while the dominating taxa associated to phyllosphere were Pseudomonadaceae (54%), Moraxellaceae (16%) and Enterobacteriaceae (25%) with Alkanindiges, Pantoea and a group of Enterobacteriaceae unclassified at genus level. The preferential occurrence of enterics in the phyllosphere was the most significant difference between both habitats. Additional enhancement of enterics on the phyllosphere was observed in bottom rot diseased lettuce plants, while Acinetobacter and Alkanindiges were identified as indicators of healthy plants. Interestingly, the microbial diversity was enhanced by trea tment with both the pathogen, and the co-inoculated biological control agent. The highest impact and bacterial diversity was found by Rhizoctonia inoculation, but FZB42 lowered the impact of Rhizoctonia on the microbiome. This study shows that the indigenous microbiome shifts as a consequence to pathogen attack but FZB42 can compensate these effects, which supports their role as biocontrol agent and suggests a novel mode of action © 2014 Erlacher, Cardinale, Grosch, Grube and Berg.
Muller T.,Leibniz Center for Agricultural Landscape Research |
Ruppel S.,Leibniz Institute of Vegetable and Ornamental Crops
FEMS Microbiology Ecology | Year: 2014
Most microorganisms of the phyllosphere are nonculturable in commonly used media and culture conditions, as are those in other natural environments. This review queries the reasons for their 'noncultivability' and assesses developments in phyllospere microbiology that have been achieved cultivation independently over the last 4 years. Analyses of total microbial communities have revealed a comprehensive microbial diversity. 16S rRNA gene amplicon sequencing and metagenomic sequencing were applied to investigate plant species, location and season as variables affecting the composition of these communities. In continuation to culture-based enzymatic and metabolic studies with individual isolates, metaproteogenomic approaches reveal a great potential to study the physiology of microbial communities in situ. Culture-independent microbiological technologies as well advances in plant genetics and biochemistry provide methodological preconditions for exploring the interactions between plants and their microbiome in the phyllosphere. Improving and combining cultivation and culture-independent techniques can contribute to a better understanding of the phyllosphere ecology. This is essential, for example, to avoid human-pathogenic bacteria in plant food. © 2013 The Authors.
Franken P.,Leibniz Institute of Vegetable and Ornamental Crops |
Franken P.,Humboldt University of Berlin
Applied Microbiology and Biotechnology | Year: 2012
The successful conversion of plant production systems from conventional resource-exhausting to sustainable strategies depends on knowledge-based management of environmental factors. Root-inhabiting fungi came more and more into focus because their hyphae connect in ideal manner resources and challenges of the surrounding with the plant. A paradigm for such root endophytes is presented by the basidiomycete Piriformospora indica. This fungus possesses a broad host spectrum and positively affects different aspects of plant performance. This so far unique combination of attributes makes P. indica and its close relatives among the Sebacinales very interesting tools for cultivation of various crops. This review will outline the different aspects required to apply this root endophyte in agri- and horticulture concerning plant growth, plant nutrition and plant defence or tolerance thereby explaining what is known about the biological basis for the observed effects. Open questions and challenges for successful inoculum production and application will be discussed. © Springer-Verlag Berlin Heidelberg 2012.
Klaring H.-P.,Leibniz Institute of Vegetable and Ornamental Crops |
Krumbein A.,Leibniz Institute of Vegetable and Ornamental Crops
Journal of Agronomy and Crop Science | Year: 2013
Recent studies propose the combination of electrical energy and plant production, in which often only radiation peaks were used for energy production. Then, the effect on plant growth is assumed to be negligible. However, photosynthesis is known to be a monotonically increasing function of radiation. We studied the response of tomato to constraining the intensity of solar radiation. Tomato crops in greenhouse compartments were shaded when the outside photosynthetic photon flux density (PPFD) exceeded 640 and 1280 μmol m-2 s-1, resulting in a 57 % and 34 % reduction in the PPFD integral over the growing period compared to the non-shaded control. Constraining the intensity of solar radiation significantly reduced photosynthesis, growth and yield of tomato plants. Model-derived estimates of reduction in crop dry matter increment were 50 % and 28 % for the strongly and moderately PPFD constrained crops. However, measured plant dry matter increment decreased only by 31 % and 19 %, respectively, that is, light use efficiency increased markedly. This indicates a strong adaptation of the plant's metabolism to cope with the limitation in light availability such as increasing the specific leaf area and reducing respiration. Surprisingly, this was only of little concern to the fruit quality, because no effect of constraining PPFD on the concentration of total dry matter, sugars and lycopene in the fruits could be observed. The concentration of titratable acids was significantly increased, however, when constraining PPFD, while ß-carotene was slightly decreased. When combining plant and energy production, yield reductions in systems that reduce the supply of solar radiation to crops only at high irradiances will be less considerable than in systems that permanently shade the crop. However, yield losses in tomato production remain significant in both system types. © 2013 Blackwell Verlag GmbH.
Ruppel S.,Leibniz Institute of Vegetable and Ornamental Crops
Communications in Soil Science and Plant Analysis | Year: 2013
Plant growth-promoting rhizobacteria (PGPR) may enhance the plant availability of phosphorus (P) in soil. A greenhouse pot experiment was conducted cultivating maize (Zea mays L.) on a P-deficient soil. Three bacterial treatments (control without PGPR and application of either Enterobacter radicincitans sp. nov. strain DSM 16656 or Pseudomonas fluorescens strain DR54) were tested in conjunction with three P treatments [no P addition, inorganic P as triplesuperphosphate (TSP), and organic P as phytin] at two different growth stages of maize (V6 and V9). Amendment with TSP enhanced growth, P uptake, and highly bioavailable P pools in soil to a greater extent than phytin. In contrast, arbuscular mycorrhiza (AM) formation of maize roots after phytin application doubled those for the TSP treatment or the control without P. Application of PGPR was also able to increase AM formation and P uptake of maize, especially when no P source was added. Furthermore, P. fluorescens inoculation resulted in an increase of highly soluble soil P pools at the early growth stage. Greater impacts of phytin on P nutrition of maize may exist in a longer term as a result of slow P release and promotion of AM fungi. Benefits to maize P nutrition derived from PGPR application can be expected under P deficiency. © 2013 Copyright Taylor and Francis Group, LLC.
Ruehlmann J.,Leibniz Institute of Vegetable and Ornamental Crops
Archives of Agronomy and Soil Science | Year: 2013
The Box Plot Experiment in Grossbeeren was set up in 1972 to investigate the efficiency of diverse fertilization strategies within an irrigated vegetable crop rotation system for three different soils. Here, we report on the long-term effects on nitrogen, carbon and energy balances of applying various organic amendments and different amounts of mineral N fertilizer to soils. Fertile soils (sandy loam and clayey silt) were characterized by higher yield and N removal potential by plants, higher acceptable N input amounts, and a higher proportion of total N input recovered by soil N storage and N uptake by plants. After 40 years, organic carbon equilibrium in the soil has not been reached. Rates of change of organic carbon stocks are still affected by the different organic matter levels at the beginning of the experiment. An increasing net N supply increased and organic C input decreased net C gains. Because of the manifold possibilities of producing energy from current or former agricultural land, energetic evaluation of land use needs to become more complex if direct comparisons are to be made. Including the energy contents of organic amendments and soil organic matter in the energy balances would be a first step in this direction. © 2013 Copyright Taylor and Francis Group, LLC.
Welter S.,Leibniz Institute of Vegetable and Ornamental Crops
Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology | Year: 2013
Tomato became one of the world-wide most consumed vegetables, unfortunately accompanied by an increasing risk of tomato allergy affecting certain people. As tomato allergic subjects show highly variable reactions in clinical allergy tests, it is difficult to identify cultivars or differentially treated tomato plants where a significant reduction in the allergenic potential over all subjects of a cohort can be detected. This study was carried out to test the hypothesis that individual variability is based on differential reactions of single subjects to particular allergens in tomato fruits of plants with certain genetic background or cultivated under distinct conditions. Proteins were extracted from tomato fruits of the previously investigated genotypes 76R, its mycorrhizal mutant RMC, and the cultivar Counter, fertilized with different forms of nitrogen in deficit or excess. 2-D immunoblots were carried out with sera of nine tomato allergic subjects, beforehand analysed in skin prick tests. In total, ten putative tomato allergens were identified in these immunoblots. No correlation was detected between individual skin prick test results and the quantity of positive reactions to putative allergens. IgEs of each subject showed reactions to nearly every identified putative allergen, but reactions were dependent on genotype and growth conditions. Among the ten putative tomato allergens, five new candidates were identified as follows: an endo-β-mannanase, a pectinacetylesterase, a pectinesterase inhibitor, an aspartyl protease family protein and a protein of unknown function. The hypothesis that high interindividual differences in allergic reactions are based on the interactions between the IgEs of allergic subjects with particular allergens has to be rejected. However, five proteins with putative clinical relevance as tomato allergens could be newly identified. © 2013 John Wiley & Sons Ltd.