Entwicklung von Maissorten mit spezieller Anpassung an die Bedingungen des Ökologischen Landbaus

Organic farming has gained in importance in Germany during the past years. Therefore an increasing demand exists for varieties with specific adaptation to this farming system. Hence it becomes necessary for plant breeders to optimize their selection strategy for varieties which meet the requirements of organic farming. For this purpose a research project was conducted at the University of Hohenheim, Institute of Plant Breeding, Seed Science, and Population Genetics in cooperation with the KWS SAAT AG. It was supported by the “Bundesprogramm Ökologischer Landbau” and lasted from April 2004 to December 2006. In the present contribution the results of comparative trials with maize under organic and conventional farming conditions in 2004 and 2005 are reported. It is demonstrated that under organic farming maize genotypes can be evaluated with similar precision as under conventional conditions. However, inconsistent correlations between the two farming systems indicate that the predictability of performance under organic farming from data obtained under conventional farming and vice versa strongly depends on the genetic materials

Theoretical Model for Cellular Shapes Driven by Protrusive and Adhesive Forces

The forces that arise from the actin cytoskeleton play a crucial role in determining the cell shape. These include protrusive forces due to actin polymerization and adhesion to the external matrix. We present here a theoretical model for the cellular shapes resulting from the feedback between the membrane shape and the forces acting on the membrane, mediated by curvature-sensitive membrane complexes of a convex shape. In previous theoretical studies we have investigated the regimes of linear instability where spontaneous formation of cellular protrusions is initiated. Here we calculate the evolution of a two dimensional cell contour beyond the linear regime and determine the final steady-state shapes arising within the model. We find that shapes driven by adhesion or by actin polymerization (lamellipodia) have very different morphologies, as observed in cells. Furthermore, we find that as the strength of the protrusive forces diminish, the system approaches a stabilization of a periodic pattern of protrusions. This result can provide an explanation for a number of puzzling experimental observations regarding cellular shape dependence on the properties of the extra-cellular matrix

Quantitative genetic studies on breeding maize for adaptation to organic farming

Organic farming has gained in importance in Germany during recent years.Therefore an increasing demand exists for varieties with specific adaptation to this farming system. In the present study we therefore conducted comparative field experiments with modern maize breeding materials under organic versus conventional farming conditions (ORGandCON, respectively) to estimate quantitative genetic parameters needed for developing optimal breeding strategies and to investigate the perspectives of selection for specific adaptation to ORG. Starting from two broad samples of elite germplasm, consisting of 178 flint and dent lines, respectively, fractions of 11 flint and 11 dent lines were selected based on their testcross performance under ORG. A corresponding set of lines was selected under CON. Testcross performance was evaluated in three regions of Germany and selection of superior lines was practiced across two stages in 2004 and 2005, respectively. The specifically selected lines were crossed in a factorial manner for production of experimental interpool single-cross hybrids which were field-tested under ORG and CON in two regions in 2006. Average grain yields were about 16% lower under ORG than under CON.Variance components and entry-mean heritability coefficients under ORG largely resembled those obtained under CON. Phenotypic correlations between ORGandCONweremoderate for grain yield and strong for grain dry matter content. No consistent estimates were obtained for the corresponding genotypic correlation for grain yield. At the first stage of testcross selection no evidence of specific adaptation to ORG or CON was observed whereas the factorial crosses tested in 2006 displayed distinct, yet non-significant, advantages when evaluated under the respective target farming system. A small top fraction of hybrids showed outstanding performance under both ORG and CON. The chances of detecting such broadly adapted genotypes are increased if ORG test sites are included in the regular testing system. Quelle: Burger, H. et. al (2008): Quantitative genetic studies on breeding maize for adaptation to organic farming. Euphytica 163(3): S. 501-510

Whole-brain 3D mapping of human neural transplant innervation

While transplantation represents a key tool for assessing in vivo functionality of neural stem cells and their suitability for neural repair, little is known about the integration of grafted neurons into the host brain circuitry. Rabies virus-based retrograde tracing has developed into a powerful approach for visualizing synaptically connected neurons. Here, we combine this technique with light sheet fluorescence microscopy (LSFM) to visualize transplanted cells and connected host neurons in whole-mouse brain preparations. Combined with co-registration of high-precision three-dimensional magnetic resonance imaging (3D MRI) reference data sets, this approach enables precise anatomical allocation of the host input neurons. Our data show that the same neural donor cell population grafted into different brain regions receives highly orthotopic input. These findings indicate that transplant connectivity is largely dictated by the circuitry of the target region and depict rabies-based transsynaptic tracing and LSFM as efficient tools for comprehensive assessment of host–donor cell innervation

Bridging archaeology and GIS: influencing factors for a 4D archaeological GIS

In archaeology, the intensive application of Geographical Information Systems (GIS) with their specialized capabilities in analysing spatial objects and relations, is hampered by the data particularities. Consequently, the idea arises to develop a comprehensive four-dimensional (4D, i.e. 3D and time) GIS tailored to archaeology, which would facilitate simultaneously handling the spatial and temporal dimensions. This paper endeavours to propose a methodological framework for the development of such a 4D archaeological GIS. This methodology is centred on the usability of the system and therefore integrates a methodology based on human cognition and the approach of the user-centred design cycle. The proposed framework consists of three pillars: (i) the user-oriented, (ii) data-oriented and (iii) analysis-oriented pillar