Performance of winter wheat varieties in white clover living mulch

The choice of variety for agricultural systems with multiple crops may differ from the one used in sole crop because of the changes in environmental conditions brought about by interspecific plant competition. Information about varietal performance under living mulch conditions as well as the suitability of the results of the official variety testing, conducted under conventional cropping conditions, for such systems is lacking for small grain cereals such as winter wheat (Triticum aestivum L.). In the current study, nine different winter wheat varieties were established in an existing living mulch of white clover (Trifolium repens L.) in three trials in the Swiss Midlands in the years 2003 and 2004. The winter wheat was directly sown in widely spaced rows (0.375 m) at a density of 450 viable grains m–2. Grain yield varied between 1.83 and 4.11 Mg ha–1. Plant height was correlated (r = 0.92, p < 0.001) with the grain yield, suggesting that varieties with long shoots may have an advantage because of the more ntense shading of the white clover plants. However, the best yielding varieties were also those with the most intense tillering. Recorded values of grain quality traits (grain weight, test weight and protein content) for the tested varieties were analogous under the living mulch conditions of the current trials to those obtained in the official variety testing. This analogy was not observed for the grain yield, except for one trial, where the competitive strength of the white clover was reduced by mechanical interference prior to the seeding of the wheat, which positively affected tillering and hence grain yield. Thus, the use of better yielding varieties of winter wheat in living mulches is at the cost of decreased grain quality. The combination of yield and quality goals in living mulch systems will rather depend on the minimization of the competition of the cover crop on the wheat plants than on the variety choice following recommendations based on trials conducted under conventional cropping conditions

Pharmaceutical Risk and the Quality of Life

Quality-of-life research is briefly described and said to be in its infancy. However, the authors observe that such studies may, e.g., make it possible to better match patients and therapies. They also predict that, as scientific difficulties are overcome, the pharmaceutical industry will become more active in planning, implementing and evaluating such research

The Targeting of the atToc159 Preprotein Receptor to the Chloroplast Outer Membrane is Mediated by its GTPase Domain and is Regulated by GTP

The multimeric translocon at the outer envelope membrane of chloroplasts (Toc) initiates the recognition and import of nuclear-encoded preproteins into chloroplasts. Two Toc GTPases, Toc159 and Toc33/34, mediate preprotein recognition and regulate preprotein translocation. Although these two proteins account for the requirement of GTP hydrolysis for import, the functional significance of GTP binding and hydrolysis by either GTPase has not been defined. A recent study indicates that Toc159 is equally distributed between a soluble cytoplasmic form and a membrane-inserted form, raising the possibility that it might cycle between the cytoplasm and chloroplast as a soluble preprotein receptor. In the present study, we examined the mechanism of targeting and insertion of the Arabidopsis thaliana orthologue of Toc159, atToc159, to chloroplasts. Targeting of atToc159 to the outer envelope membrane is strictly dependent only on guanine nucleotides. Although GTP is not required for initial binding, the productive insertion and assembly of atToc159 into the Toc complex requires its intrinsic GTPase activity. Targeting is mediated by direct binding between the GTPase domain of atToc159 and the homologous GTPase domain of atToc33, the Arabidopsis Toc33/34 orthologue. Our findings demonstrate a role for the coordinate action of the Toc GTPases in assembly of the functional Toc complex at the chloroplast outer envelope membrane

Plant species dominance shifts across erosion edge-meadow transects in the Swiss Alps

While exerting no obvious function under "average” environmental conditions, the presence of certain plant specialists becomes crucial in the event of a complete failure of a community due to severe disturbance such as landslides. Plants capable of growing at erosion edges may act as potential edge-engineers by coping with unstable ground and stabilizing the soil with their roots. We hypothesized that life conditions at erosion edges select for a particular set of specialists or species with specific traits, the identification of which was the aim of the study. Across 17 small-scale transects (0.40 × 1.60 m) from intact meadows to landslide edges (Ursern Valley, Swiss Alps, c. 1,600 m a.s.l.), we quantified plant species abundance by the point intercept method and characterized growth conditions based on Landolt's indicator values, leaf δ13C, and volumetric soil moisture in the uppermost soil layers. We observed a clear change of plant species composition and relative abundance from the meadow to the edge, presumably induced by the 25 % lower soil moisture and microclimatic exposure. Species richness at the edge was two-thirds of that in the meadow, but was positively correlated with species richness of the adjacent meadow. Species with "edge-preference” had either (1) rolled or festucoid leaves like Festuca spp., Avenella flexuosa and Nardus stricta, or (2) small, scleromorphic leaves like Vaccinium vitis-idaea, Calluna vulgaris and Thymus ssp. Graminoids with rolled/festucoid leaves were found to be the most dominant edge-specialists. The grass Festuca valesiaca s.l. emerged as the most dominant plant species at the edge, having an 11-times higher cover at the edge than in the meadow. In this montane grassland, a single species contributes to the stabilization of erosion edges and may be regarded as a potential keystone species for slope stability and regeneration after landslides even its role has not so far been establishe

Low temperature limits for root growth in alpine species are set by cell differentiation

Plant growth in cold climates is not limited by carbon assimilation (source activity) but rather by reduced carbon investment into new tissues (sink limitation). It has been hypothesized that all cold-adapted plants face similar growth constraints at low temperature mainly associated with the formation of new tissues. To explore the thermal limitation of plant tissue formation, we studied root growth and anatomical root tissue characteristics in four cold-adapted alpine species (Ranunculus glacialis, Rumex alpinus, Tussilago farfara, Poa alpina), grown in thermostated soils with a vertical temperature gradient approaching 1 °C. Above-ground plant organs were exposed to typical alpine climate conditions (high solar radiation and cool nights) at 2440 m a.s.l. in the Swiss Alps to assure continuous source activity. Image-based measurements of root growth (root elongation rates at 12-h intervals, RERs) were combined with anatomical examinations in thermally constrained root tips as well as with a functional growth analysis of entire plants. Temperatures in the range 0.8 to 1.4 °C were denoted as critically low temperature thresholds for root formation across the four species. The RERs per 12 h revealed that roots kept extending at low rates at 0.7-1.2 °C but cell elongation and xylem lignification were clearly inhibited in the terminal zones of root tips. Roots exposed to temperatures between 1 and 5 °C showed strongly reduced elongation rates so that these roots contributed very little to the entire root system compared to control roots grown at 10 °C. Hardly any secondary roots were formed at temperatures below 5 °C and total root mass was substantially lower (74 % reduction in comparison to control), also the above-ground biomass was reduced by 23 %. Cell elongation and differentiation rather than cell division control length and shape of root cells at the low temperature limit of growth. Lignification of root xylem is clearly constrained at temperatures below 3 °C

Einfluss von lebenden Mulchen auf die Begleitflora und die Weizenerträge unter Bedingungen des Ökolandbau

For the success of no-tillage in organic farming, new tools have to be developed to control weeds. One possible strategy could be sowing the main crop into an earlier established living mulch of easily controllable cover crops. Field trials were carried out in the Swiss midlands to investigate the impact of different legume cover crops on weed populations and grain yield of directly drilled winter wheat (Triticum aestivum L.) in a living mulch system. In general, weed suppressing effect was best with highly productive legumes. A significant reduction of the weed density of dicotyle, monocotyle, and spring germinating species was observed. Though, effective weed suppression resulted also in strong competition with the winter wheat. In order to improve the practicability of such systems, seeding technique of the main crop and living mulch management should be investigated

Comparison of bread wheat varieties with different breeding origin under organic and low input management

The aims of the study were to compare 37 bread wheat varieties with different breeding origin under conventional and organic farming conditions in Hungary and Austria for three years and to identify traits highly sensitive to management systems that could be separated according to their suggested selecting environments. According to the results, heading date, sensitivity to leaf rust and powdery mildew had high heritability, thus, for economic reasons, it is reasonable to select for these traits in conventional fields even if the selection target is organic agriculture. On the contrary, selection for grain yield, test weight, leaf-inclination and vigorous growth should be done later in the target environment. It was concluded that the selecting environment has measurable effects on the performance of bread wheat varieties. Our results could help organic breeders in their selection work, especially in the continental climatic zone of Europe

Heritabilität und Korrelationen von Morphologischen Eigenschaften bei Winterweizen-Sorten unter Bio-Bedingungen

Die untersuchten morphologischen Merkmale weisen insgesamt eine niedrigere Heritabilität und eine geringe Korrelation mit Kornertrag auf. Dies weist darauf hin, dass sich diese Merkmale nur bedingt als Selektionsmerkmal und zur Sortenbeschreibung eignen. Aber auch wenn nur ein geringer positiver Zusammenhang mit dem Kornertrag erkennbar ist, kann sich z.B. ein höherer Bodenbedeckungsgrad auf lange Frist die Menge der Unkrautsamen im Boden verringern. Der positive Zusammenhang von Pflanzenhöhe und Ertrag ist teilweise durch eine bessere Gesundheit hoher Pflanzen zu erklären

Eignung von neuen Sommerölleinsorten für den Ökolandbau im Schweizer Mittelland

Oil flax was cropped in Switzerland in former times but seldom today. To investigate new varieties with respect to their agronomic performance and suitability for the production of cold-pressed oil, 15 varieties of spring flax were tested in the years 2005-2007 at one site. They were sown in small plots with four replicates and managed according the rules of Swiss organic farming. Averaged over the years, seed yield of the varieties ranged from 1.4 - 1.9 t/ha. Pressure of pests and diseases were generally low and weeds were controlled successfully by mechanical means. In order to recommend flax varieties for the production of oil, oil quality aspects need to be considered and investigated carefully