Scientific goals and experiments of the project “winter precipitation at Mount Rigi”: An overview

Wet deposition plays an important role as a mechanism for cleansing of the polluted troposphere. Fluxes of pollutants from the atmosphere to earth's surface can affect soil and aquatic ecosystems. The investigation of the pollutant incorporation into wet deposition is therefore of considerable interest for environmental research. The project “Winter precipitation at Mount Rigi” addresses the processes determining the chemical composition of wet deposition through an integrated approach considering atmospheric physical and chemical processes and their complex interactions. The investigated topics include: aerosol and gas scavenging, atmospheric chemistry (cloud water chemistry), cloud physics and dynamics. The design of the experiment, using three ground based measuring stations at the northwestern slope of the mountain, and the conceptual ideas using case study investigations are discussed.     

Flooding tolerance of spelt (Triticum spelta L.) compared to wheat (Triticum aestivum L.) – A physiological and genetic approach

In marginal, agroclimatic zones, yield is often affected by flooding, but the effect is much less for winter spelt (Triticum spelta L.) than for winter wheat (Triticum aestivum L.). This study evaluates the reaction of a wheat x spelt population (F₅ RILs of Forno x Oberkulmer) to flooding stress in the early phase of germination. Lines with greater tolerance to 48 h flooding just after imbibition showed less electrolyte leakage (r = -0.79) indicating greater membrane integrity and better survival. Five QTL explaining 40.6% of the phenotypic variance for survival to flooding were found, and localized on the chromosomes 2B, 3B,5A, and 7S. The tolerance to 48 h flooding four days after sowing was best correlated with the mean germination time (r = 0.8), indicating that the plants with a fast coleoptile growth during flooding are less susceptible to flooding. Ten QTL were found for seedling growth index after flooding explaining 35.5% of the phenotypic variance. They were localized on chromosomes 2A, 2B, 2D, 3A, 4B, 5A, 5B, 6A, and 7S. Standard varieties of spelt and wheat showed the same tolerance characteristics. The possibility to use marker assisted selection for flooding tolerance is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Impacts of population growth, economic development, and technical change on global food production and consumption

Over the next decades mankind will demand more food from fewer land and water resources. This study quantifies the food production impacts of four alternative development scenarios from the Millennium Ecosystem Assessment and the Special Report on Emission Scenarios. Partially and jointly considered are land and water supply impacts from population growth, and technical change, as well as forest and agricultural commodity demand shifts from population growth and economic development. The income impacts on food demand are computed with dynamic elasticities. Simulations with a global, partial equilibrium model of the agricultural and forest sectors show that per capita food levels increase in all examined development scenarios with minor impacts on food prices. Global agricultural land increases by up to 14% between 2010 and 2030. Deforestation restrictions strongly impact the price of land and water resources but have little consequences for the global level of food production and food prices. While projected income changes have the highest partial impact on per capita food consumption levels, population growth leads to the highest increase in total food production. The impact of technical change is amplified or mitigated by adaptations of land management intensities.     

Isolation,partial identification and application of diazotrophic rhizobacteria from traditional Indian rice cultivars

A diversity of N₂-fixing (diazotrophic) bacteria was isolated from two traditional rice cultivars, Sataria and Kartiki, from the rice growing area of Mithila region of North Bihar, India, where low levels of nitrogen fertilizers are applied. Nitrogen-free semisolid media NFb, JMV and LGI with different carbon sources and pH-values were used for enrichment and isolation of root-associated diazotrophs. The colonization density of roots by diazotrophs, as estimated from positive pellicle formation at highest dilution in nitrogen-free enrichment media, was 10⁶–10⁸ diazotrophic bacteria per g fresh root weight. Roots of the cultivar Kartiki were found to be more densely colonized endophytically by diazotrophs as detected after chloramine T (1%) surface disinfection. To ascertain the phylogenetic affiliation of the isolates, phylogenetic oligonucleotide probes and the Fluorescent in situ Hybridization (FISH) technique were applied. Using group-specific rRNA directed oligonucleotide probes, the majority of the isolates could be identified as alpha-, beta-, or gamma-proteobacteria. Using 16S and 23S rRNA-directed genus- or species-specific probes, Herbaspirillum seropedicae, Azospirillum amazonense, Burkholderia cepacia/vietnamiensis, Rhizobia and Pseudomonas spp. were found to be the most prominent root associated culturable diazotrophs. Diazotrophic Gluconacetobacter spp. were also demonstrated as colonizers of rice roots. Burkholderia cenocepacia, Pseudomonas sp. and three diazotrophic PGPR reference strains were used for the inoculation of axenically grown rice seedlings to determine the plant growth promoting potential. Significant increases in the shoot length (up to 60%), shoot dry weight (up to 33%) and the grain yield (up to 26%) per plant were observed in non-axenic pot and field trials. Using semisolid enrichment media after surface sterilization of field grown inoculated rice roots and oligonucleotide probing of the diazotrophic enrichment cultures, a sustainable colonization with the inoculated bacteria could be demonstrated.     

Seasonal development of biomass yield in grass–legume mixtures on different soils and development of above- and belowground organs of Medicago sativa

Grass–legume mixtures are suitable for crop rotations under organic farming. Little attention has been paid to seasonal development of mixtures with alfalfa under field conditions. We investigated the effects of site and cut on herbage and belowground biomass yields of grass–legume mixture and on above- and belowground traits of Medicago sativa. Six sites in southern Germany were monitored during 2011. Dry matter herbage yield ranged from 9 to 16 t ha^?1. The total herbage yield of three cuts per year decreased from 45% to 36% and 19%. The belowground biomass in the upper 30 cm soil layer ranged from 1.7 to 3.8 t ha^?1.There was no seasonal trend. Diameter of the root neck and maximum order of branching of alfalfa increased during the season. The number of nodules per plant decreased from 9.5–17.0 in May to 7.5–13.0 in August. By the last cut, roots with larger diameter created smaller nodules. More branched roots created more nodules independent of their shape. Thinner roots have more active nodules. Plant height, number of stems and inflorescences per plant were higher in July and August than in May. In conclusion, a holistic analysis including above- and belowground traits should be used for the evaluation of fodder crops.     

Phospholipid-based microemulsions suitable for use in foods

The preparation of nonaqueous microemulsions using food-acceptable components is reported. The effect of oil on the formation of microemulsions stabilized by lecithin (Epikuron 200) and containing propylene glycol as immiscible solvent was investigated. When the triglycerides were used as oil, three types of phase behavior were noted, namely, a two-phase cloudy region (occurring at low lecithin concentrations), a liquid crystalline (LC) phase (occurring at high surfactant and low oil concentrations), and a clear monophasic microemulsion region. The extent of this clear one-phase region was found to be dependent upon the molecular volume of the oil being solubilized. Large molecular volume oils, such as soybean and sunflower oils, produced a small microemulsion region, whereas the smallest molecular volume triglyceride, tributyrin, produced a large, clear monophasic region. Use of the ethyl ester, ethyl oleate, as oil produced a clear, monophasic region of a size comparable to that seen with tributyrin. Substitution of some of the propylene glycol with water greatly reduced the extent of the clear one-phase region and increased the extent of the liquid crystalline region. In contrast, ethanol enhanced the clear, monophasic region by decreasing the LC phase. Replacement of some of the lecithin with the micelle-forming nonionic surfactant Tween 80 to produce mixed lecithin/Tween 80 mixtures of weight ratios (Km) 1:2 and 1:3 did not significantly alter the phase behavior, although there was a marginal increase in the area of the two-phase, cloudy region of the phase diagram. The use of the lower phosphatidylcholine content lecithin, Epikuron 170, in place of Epikuron 200 resulted in a reduction in the LC region for all of the systems investigated. In conclusion, these studies show that it is possible to prepare one-phase, clear lecithin-based microemulsions over a wide range of compositions using components that are food-acceptable.     

Real‐time PCR detection of Erwinia amylovora on blossoms correlates with subsequent fire blight incidence

Fire blight is the most devastating bacterial disease of rosaceous plants. Forecasting fire blight infections is important to allow for countermeasures that reduce economic damage in pome fruit production. Current computerized forecasting models are solely based on physical factors such as temperature and moisture, but not on the actual presence of the pathogen Erwinia amylovora. Although the inoculum concentration is considered to be crucial for infection and disease outbreak, most current approaches used for identification of fire blight inoculum including morphological, biochemical, serological, and DNA‐based methods are nonquantitative. Based on a real‐time PCR approach previously published, an improved protocol to be used directly on whole bacteria in the field is described. The method allows for early detection and quantification of the pathogen prior to the occurrence of first symptoms. There is a clear correlation between bacterial abundance and subsequent disease development. However, in some cases, no disease symptoms could be observed despite a pathogen load of up to 3·4 × 10⁶ cells per blossom. Integration of the amount of pathogen detected into refined prediction algorithms may allow for the improvement of applied forecasting models, finally permitting a better abatement of fire blight.     

Flystrike prevention on Merino lambs with the insect growth regulator dicyclanil

The efficacy of a ready-to-use 5% dicyclanil pour-on formulation as a preventative of natural flystrike on Merino lambs was investigated in a field trial involving 5 sites in the southern Cape Province. A total of 1,804 lambs treated with dicyclanil were compared with 882 untreated control lambs for up to 25 weeks after treatment. Efficacy was assessed by calculating the weekly cumulative strike rate at each site and aggregated for all sites, as well as by calculating the percentage reduction achieved in treated lambs. Cumulative strike rates for the untreated controls aggregated for all sites at Weeks 9,14 and 19 after treatment reached 6.2, 12.8 and 17.8%, respectively, compared with 0.4, 1.7 and 3.6% for the dicyclanil treated lambs. Percentage control aggregated for all sites at Weeks 9,14 and 19 after treatment was 93, 87 and 80%, respectively. Heavy rains during the 1st half of the trial did not substantially reduce the efficacy of the product.     

Microbial activity and bacterial composition of H2-treated soils with net CO2 fixation

The effects of H₂ gas treatment of an agricultural soil cultivated previously with a mixture of clover (Trifolium pratense) and alfalfa (Medicago sativa) on CO₂ dynamics and microbial activity and composition were analyzed. The H₂ emission rate of 250 nmol H₂ g⁻¹ soil h⁻¹ was similar to the upper limit of estimated H₂ amounts emitted from N₂ fixing nodules into the surrounding soil ([Dong, Z., Layzell, D.B., 2001. H₂ oxidation, O₂ uptake and CO₂ fixation in hydrogen treated soil. Plant and Soil 229, 1-12.]). After 1 week of H₂ supply to soil samples simultaneously with H₂ uptake net CO₂ production declined continuously and this finally led to a net CO₂ fixation rate in the H₂-treated soil of 8 nmol CO₂ g⁻¹ soil h⁻¹. The time course of H₂ uptake and CO₂ fixation in the soils corresponded with an increase in microbial activity and biomass of the H₂-treated soil determined by microcalorimetric measurements, fluorescence in situ hybridization analysis (FISH) and DNA staining (DAPI). Shifts in the bacterial community structure caused by the supply of H₂ were recorded. While the H₂ treatment stimulated β-and γ-subclasses of Proteobacteria, it had no significant effect on α-Proteobacteria. In addition, FISH-detectable bacteria of the Cytophaga-Flavobacterium-Bacteroides phylum increased in numbers.     

Cleavage products of lycopene produced by in vitro oxidations: characterization and mechanisms of formation

The aim of this study was to produce in vitro oxidation products of lycopene, which could be possible in vivo metabolites. An oxidation of lycopene with potassium permanganate gave a range of lycopene degradation compounds resulting from the oxidative cleavage of one or two carbon-carbon double bonds. Eleven apo-lycopenals/ones and six apo-carotendials were obtained and tentatively characterized by HPLC-DAD-MS. Apo-11-lycopenal and apo-8,6'-carotendial were isolated and characterized by (1)H NMR for the first time. Lycopene was submitted to an oxidation by atmospheric oxygen catalyzed by a metalloporphyrin, a model system of the active center of cytochrome P450 enzymes. (Z)-Isomers, monoxides, and cleavage compounds of (E)-lycopene were formed. We propose a mechanism of oxidation of lycopene by this system.