Showing papers by "University of Hohenheim published in 2010"

The German bee monitoring project: a long term study to understand periodically high winter losses of honey bee colonies

Abstract: The Western honey bee, Apis mellifera, is the most important animal pollinator in agriculture worldwide providing more than 90% of the commercial pollination services. Due to the development in agriculture the demands for honey bee pollination are steadily increasing stressing the pollination capacity of the global managed honey bee population. Hence, the long-term decline of managed honey bee hives in Europe and North-America is of great concern and stimulated intensive research into the possible factors presumably causing honey bee colony collapse. We here present a four-year study involving more than 1200 bee colonies from about 120 apiaries which were monitored for the entire study period. Bee samples were collected twice a year to analyze various pathogenic factors including the ectoparasitic mite Varroa destructor, fungi (Nosema spec., Ascosphaera apis), the bacterium Paenibacillus larvae, and several viruses. Data on environmental factors, beekeeping management practice, and pesticides were also collected. All data were statistically analyzed in respect to the overwintering mortality of the colonies. We can demonstrate for several factors that they are significantly related to the observed winter losses of the monitored honey bee colonies: (i) high varroa infestation level, (ii) infection with deformed wing virus (DWV) and acute bee paralysis virus (ABPV) in autumn, (iii) queen age, and (iv) weakness of the colonies in autumn. No effects could be observed for Nosema spec. or pesticides. The implications of these findings will be discussed.

Soil type and land use intensity determine the composition of arbuscular mycorrhizal fungal communities

Abstract: The objective of this study was to test whether soil types can be characterized by their arbuscular mycorrhizal fungal (AMF) communities. To answer this question, a well-defined study area in the temperate climatic zone of Central Europe was chosen with a large spectrum of soils and parent materials. Representative soil samples were taken from three soil types (Cambisol, Fluvisol and Leptosol) at in total 16 sites differing in agricultural land use intensity (9 grasslands and 7 arable lands). AMF spores were isolated and morphologically identified directly from field soils and after reproduction in trap cultures. AMF diversity and community composition strongly depended on soil type and land use intensity, and several AMF species were characteristic for a specific soil type or a specific land use type and hence had a specific niche. In contrast, other AM fungi could be considered as ‘generalists’ as they were present in each soil type investigated, irrespective of land use intensity. An estimated 53% of the 61 observed AMF species could be classified as ‘specialists’ as (almost) exclusively found in specific soil types and/or under specific land use intensities; 28% appeared to be ‘generalists’ and 19% could not be classified. Plant species compositions (either natural or planted) had only a subordinate influence on the AMF communities. In conclusion, land use intensity and soil type strongly affected AMF community composition as well as the presence and prevalence of many AM fungi. Future work should examine how the differences in AMF species compositions affect important ecosystem processes in different soils and to which extent the loss of specific groups of AM fungi affect soil quality.

β-Carotene Is an Important Vitamin A Source for Humans

Abstract: Experts in the field of carotenoids met at the Hohenheim consensus conference in July 2009 to elucidate the current status of β-carotene research and to summarize the current knowledge with respect to the chemical properties, physiological function, and intake of β-carotene. The experts discussed 17 questions and reached an agreement formulated in a consensus answer in each case. These consensus answers are based on published valid data, which were carefully reviewed by the individual experts and are justified here by background statements. Ascertaining the impact of β-carotene on the total dietary intake of vitamin A is complicated, because the efficiency of conversion of β-carotene to retinol is not a single ratio and different conversion factors have been used in various surveys and following governmental recommendations within different countries. However, a role of β-carotene in fulfilling the recommended intake for vitamin A is apparent from a variety of studies. Thus, besides elucidating the various functions, distribution, and uptake of β-carotene, the consensus conference placed special emphasis on the provitamin A function of β-carotene and the role of β-carotene in the realization of the required/recommended total vitamin A intake in both developed and developing countries. There was consensus that β-carotene is a safe source of vitamin A and that the provitamin A function of β-carotene contributes to vitamin A intake.

Pathological aspects of lipid peroxidation

Abstract: Lipid peroxidation (LPO) product accumulation in human tissues is a major cause of tissular and cellular dysfunction that plays a major role in ageing and most age-related and oxidative stress-related diseases. The current evidence for the implication of LPO in pathological processes is discussed in this review. New data and literature review are provided evaluating the role of LPO in the pathophysiology of ageing and classically oxidative stress-linked diseases, such as neurodegenerative diseases, diabetes and atherosclerosis (the main cause of cardiovascular complications). Striking evidences implicating LPO in foetal vascular dysfunction occurring in pre-eclampsia, in renal and liver diseases, as well as their role as cause and consequence to cancer development are addressed.

Belowground carbon allocation by trees drives seasonal patterns of extracellular enzyme activities by altering microbial community composition in a beech forest soil

Abstract: Summary • Plant seasonal cycles alter carbon (C) and nitrogen (N) availability for soil microbes, which may affect microbial community composition and thus feed back on microbial decomposition of soil organic material and plant N availability. The temporal dynamics of these plant–soil interactions are, however, unclear. • Here, we experimentally manipulated the C and N availability in a beech forest through N fertilization or tree girdling and conducted a detailed analysis of the seasonal pattern of microbial community composition and decomposition processes over 2 yr. • We found a strong relationship between microbial community composition and enzyme activities over the seasonal course. Phenoloxidase and peroxidase activities were highest during late summer, whereas cellulase and protease peaked in late autumn. Girdling, and thus loss of mycorrhiza, resulted in an increase in soil organic matter-degrading enzymes and a decrease in cellulase and protease activity. • Temporal changes in enzyme activities suggest a switch of the main substrate for decomposition between summer (soil organic matter) and autumn (plant litter). Our results indicate that ectomycorrhizal fungi are possibly involved in autumn cellulase and protease activity. Our study shows that, through belowground C allocation, trees significantly alter soil microbial communities, which may affect seasonal patterns of decomposition processes.

Release of plant-borne flavonoids into the rhizosphere and their role in plant nutrition

Abstract: Plants release a multitude of organic compounds into the rhizosphere, some of which are flavonoids. These products of secondary metabolism are mainly studied for their antioxidant properties and for their role in the establishment of rhizobium-legume symbiosis; however, it has been recently demonstrated that flavonoids can also affect nutrient availability through soil chemical changes. This review will give an overview of the types and amounts of flavonoids released by roots of different plant species, as well as summarize the available knowledge on root exudation mechanisms. Subsequently, factors influencing their release will be reported, and the methodological approaches used in the literature will be critically described. Finally, the direct contribution of plant-borne flavonoids on the nitrogen, phosphorous and iron availability into the rhizosphere will be discussed.

Ammonium Triggers Lateral Root Branching in Arabidopsis in an AMMONIUM TRANSPORTER1;3-Dependent Manner

Abstract: Root development is strongly affected by the plant’s nutritional status and the external availability of nutrients. Employing split-root systems, we show here that local ammonium supply to Arabidopsis thaliana plants increases lateral root initiation and higher-order lateral root branching, whereas the elongation of lateral roots is stimulated mainly by nitrate. Ammonium-stimulated lateral root number or density decreased after ammonium or Gln supply to a separate root fraction and did not correlate with cumulative uptake of 15N-labeled ammonium, suggesting that lateral root branching was not purely due to a nutritional effect but most likely is a response to a sensing event. Ammonium-induced lateral root branching was almost absent in a quadruple AMMONIUM TRANSPORTER (qko, the amt1;1 amt1;2 amt1;3 amt2;1 mutant) insertion line and significantly lower in the amt1;3-1 mutant than in the wild type. Reconstitution of AMT1;3 expression in the amt1;3-1 or in the qko background restored higher-order lateral root development. By contrast, AMT1;1, which shares similar transport properties with AMT1;3, did not confer significant higher-order lateral root proliferation. These results show that ammonium is complementary to nitrate in shaping lateral root development and that stimulation of lateral root branching by ammonium occurs in an AMT1;3-dependent manner.

Population structure and genetic diversity in a commercial maize breeding program assessed with SSR and SNP markers

Abstract: Information about the genetic diversity and population structure in elite breeding material is of fundamental importance for the improvement of crops. The objectives of our study were to (a) examine the population structure and the genetic diversity in elite maize germplasm based on simple sequence repeat (SSR) markers, (b) compare these results with those obtained from single nucleotide polymorphism (SNP) markers, and (c) compare the coancestry coefficient calculated from pedigree records with genetic distance estimates calculated from SSR and SNP markers. Our study was based on 1,537 elite maize inbred lines genotyped with 359 SSR and 8,244 SNP markers. The average number of alleles per locus, of group specific alleles, and the gene diversity (D) were higher for SSRs than for SNPs. Modified Roger's distance (MRD) estimates and membership probabilities of the STRUCTURE matrices were higher for SSR than for SNP markers but the germplasm organization in four heterotic pools was consistent with STRUCTURE results based on SSRs and SNPs. MRD estimates calculated for the two marker systems were highly correlated (0.87). Our results suggested that the same conclusions regarding the structure and the diversity of heterotic pools could be drawn from both markers types. Furthermore, although our results suggested that the ratio of the number of SSRs and SNPs required to obtain MRD or D estimates with similar precision is not constant across the various precision levels, we propose that between 7 and 11 times more SNPs than SSRs should be used for analyzing population structure and genetic diversity.

Relationship between Hydrophobicity and Antioxidant Ability of “Phenolipids” in Emulsion: A Parabolic Effect of the Chain Length of Rosmarinate Esters

Abstract: The polar paradox predicts that hydrophobic antioxidants are more active in emulsions than their hydrophilic homologues, thus assuming a linear dependency between hydrophobicity and antioxidant capacity. In contrast, we formulate in this paper an alternative hypothesis assuming a possible nonlinear dependency. To verify this so-called "nonlinear hypothesis", the antioxidant capacity of a homologous series of rosmarinic acid and its alkyl esters (methyl, butyl, octyl, dodecyl, hexadecyl, octadecyl, and eicosyl) was evaluated using a newly developed conjugated autoxidizable triene (CAT) assay. It appeared that the antioxidant capacity increases as the alkyl chain is lengthened, with a maximum for the octyl chain, after which further chain extension leads to a collapse in antioxidant capacity. This nonlinear effect was discussed in relation to the "cutoff effect" generally observed in studies using cultured cells. This new hypothesis may provide a better understanding of the antioxidant behavior of phenolics in emulsion which is a key to develop new antioxidant strategies to protect lipid substrates from oxidation. Moreover, the lipophilization with medium chain appeared as a promising way to enhance the antioxidant capacity of phenolics since octyl rosmarinate was three times more effective than rosmarinic acid which is already one of the most powerful known phenolic antioxidant. Finally, this work paves the way for systematic investigation of the chain length effect to design new "phenolipids" in a rational fashion.

Jatropha Toxicity—A Review

Abstract: Jatropha is a nonedible oil seed plant belonging to Euphorbiaceae family. Global awareness of sustainable and alternative energy resources has propelled research on Jatropha oil as a feedstock for biodiesel production. During the past two decades, several cultivation projects were undertaken to produce Jatropha oil. In future, the increased cultivation of toxic Jatropha plants and utilization of its agro-industrial by-products may raise the frequency of contact with humans, animals, and other organisms. An attempt was thus made to present known information on toxicity of Jatropha plants. The toxicity of Jatropha plant extracts from fruit, seed, oil, roots, latex, bark, and leaf to a number of species, from microorganisms to higher animals, is well established. Broadly, these extracts possess moluscicidal, piscicidal, insecticidal, rodenticidal, antimicrobial, and cytotoxic properties, and exert adverse effects on animals including rats, poultry, and ruminants. The toxicity attributed to these seeds due to their accidental consumption by children is also well documented. An attempt was also made to identify areas that need further study. The information provided in this review may aid in enhancing awareness in agroindustries involved in the cultivation, harvesting, and utilization of Jatropha plants and its products with respect to the potential toxicity of Jatropha, and consequently in application and enforcement of occupational safety measures. Data on the wide range of bioactivities of Jatropha and its products were collated and it is hoped will create new avenues for exploiting these chemicals by the phamaceutical industry to develop chemotherapeutic agents.

Ageing, Health and Life Satisfaction of the Oldest Old: An Analysis for Germany

Abstract: This analysis uses data from the German Socio-Economic Panel and the Survey on Health, Ageing and Retirement in Europe to assess the effect of ageing and health on the life satisfaction of the oldest old (defined as 75 and older). We observe a U-shaped relationship between age and levels of life satisfaction for individuals aged between 16 and 65. Thereafter, life satisfaction declines rapidly and the lowest absolute levels of life satisfaction are recorded for the oldest old. This decline is primarily attributable to low levels of perceived health. Once cohort effects are also controlled for, life satisfaction remains relatively constant across the lifespan.

Microbial uptake of low-molecular-weight organic substances out-competes sorption in soil

Abstract: Summary Low-molecular-weight organic substances (LMWOS) such as amino acids, sugars and carboxylates, are rapidly turned over in soil. Despite their importance, it remains unknown how the competition between microbial uptake and sorption to the soil matrix affects the LMWOS turnover in soil solution. This study describes the dynamics of LMWOS fluxes (10 μm) in various pools (dissolved, sorbed, decomposed to CO2 and incorporated into microbial biomass) and also assesses the LMWOS distribution in these pools over a very wide concentration range (0.01–1000 μm). Representatives of each LMWOS group (glucose for sugars, alanine for amino acids, acetate for carboxylates), uniformly 14 C-labelled, were added to sterilized or nonsterilized soil and analysed in different pools between 1 minute and 5.6 hours after addition. LMWOS were almost completely taken up by microorganisms within the first 30 minutes. Surprisingly, microbial uptake was much faster than the physicochemical sorption (estimated in sterilized soil), which needed 60 minutes to reach quasi-equilibrium for alanine and about 400 minutes for glucose. Only acetate sorption was instantaneous. At a concentration of 100 μm, microbial decomposition after 4.5 hours was greater for alanine (76.7 ± 1.1%) than for acetate (55.2 ± 0.9%) or glucose (28.5 ± 1.5%). In contrast, incorporation into microbial biomass was greater for glucose (59.8 ± 1.2%) than for acetate (23.4 ± 5.9%) or alanine (5.2 ± 2.8%). Between 10 and 500 μm, the pathways of the three LMWOS changed: at 500 μm, alanine and acetate were less mineralized and more was incorporated into microbial biomass than at 10 μm, while glucose incorporation decreased. Despite the fact that the LMWOS concentrations in soil solution were important for competition between sorption and microbial uptake, their fate in soil is mainly determined by microbial uptake and further microbial transformations. For these substances, which represent the three main groups of LMWOS in soil, the microbial uptake out-competes sorption.

Coupling of planar chromatography to mass spectrometry

Abstract: Coupling of planar chromatography to mass spectrometry (MS) and especially ambient MS is a relatively new field of great interest. The direct sample access at ambient conditions and the feasibility to obtain mass spectra free of contamination within a minute or even within seconds greatly contributes to the progress of planar chromatography. Targeted recording of mass spectra on zones of interest is performed after evaluation of the chromatogram, thus providing high efficiency. Reported approaches for coupling are divided into elution-based and desorption-based techniques. Devices of both categories are commercially available. As a consequence of increasing importance, a rethink of the terminology of liquid chromatography with MS has to be considered.

Current statistical issues in Weed Research

Abstract: Onofri A, Carbonell EA, Piepho H-P, Mortimer AM & Cousens RD (2010) Current statistical issues in Weed Research Weed Research50, 5–24 Summary The correct design of experimental studies, the selection of the appropriate statistical analysis of data and the efficient presentation of results are key to the good conduct and communication of science The last Guidance for the use and presentation of statistics in Weed Research was published in 1988 Since then, there have been developments in both the scope of research covered by the journal and in the statistical techniques available This paper addresses the changes in statistics and provides a reference work that will aid researchers in the design and analysis of their work It will also provide guidance for editors and reviewers The paper is organised into sections, which will aid the selection of relevant paragraphs, as we recognise that particular approaches require particular statistical analysis It also uses examples, questions and checklists, so that non-specialists can work towards the correct approach Statistics can be complex, so knowing when to seek specialist advice is important The structure and layout of this contribution should help weed scientists, but it cannot provide a comprehensive guide to every technique Therefore, we provide references to further reading We would like to reinforce the idea that statistical methods are not a set of recipes whose mindless application is required by convention; each experiment or study may involve subtleties that these guidelines cannot cover Nevertheless, we anticipate that this paper will help weed scientists in their initial designs for research, in the analysis of data and in the presentation of results for publication