Two-year Investigations on Herbicide-Resistant Silky Bent Grass (Apera spica-venti L. Beauv.) Populations in Winter Wheat��Population Dynamics, Yield Losses, Control Efficacy and Introgression into Sensitive Population

In this study, the results of two-year investigations on herbicide resistance in silky bent grass (Apera spica-venti) populations are presented. Two populations of A. spica-venti were sown in a winter wheat field at the Ihinger Hof Research Station near Stuttgart in Germany in October 2008. Whole-plant bioassays conducted with both populations in the greenhouse before the field trial was set up revealed that population A was strongly resistant to acetolactate synthase (ALS)-inhibitors, whereas population B was sensitive to this group of herbicides. Each block was treated with isoproturon, fenoxaprop-P-ethyl, sulfosulfuron and meso-iodosulfuron at the recommended field dose. One treatment remained unsprayed. It was found that the average number of silky bent grass panicles was significantly higher in the second year (2010) with 343 panicles m^{? 2} in the untreated control compared to 44 panicles m^{? 2} in the first year (2009). Efficacy of both ALS-inhibitors was significantly reduced in the resistant population compared to the sensitive population. Grass-weed plants surviving treatments with ALS-inhibitors produced the same number of seeds as the untreated plants. It was found that germination rate of seeds from the resistant population was more than threefold higher than from the sensitive population. Grain yield was equal in all treatments and populations in 2009. In 2010, applications of isoproturon and fenoxaprop-P-ethyl resulted in higher grain yields, with a mean of 4.6 t ha^{? 1} compared to an average of 3.9 t ha^{? 1} in the plots treated with sulfosulfuron and meso-iodosulfuron and 4.3 t ha^{? 1} in the untreated plots. However, these differences were not statistically significant. The sensitive population of the second generation (2009/2010) was approximately 20% more tolerant to ALS-inhibitors than the sensitive population of the first generation (2008/2009) which indicates introgression of herbicide resistance traits already after one year. These results clearly show that herbicide resistance to ALS-inhibitors in silky bent grass is likely to spread rapidly causing significant economic losses. Therefore, management strategies need to be developed and tested to prevent and overcome herbicide resistance in European cereal production systems.     

Divergent cytokine responses of macrophages to Mycobacterium avium subsp. paratuberculosis strains of Types II and III in a standardized in vitro model

Based on epidemiological and clinical observations, different strains of Mycobacterium avium subsp. paratuberculosis (MAP) are suspected to significantly differ in their virulence for ruminants. In the pathogenesis of paratuberculosis, macrophages represent the principal target cell for MAP. In order to judge the ability of different MAP-genotypes to modulate macrophage responses, the cytokine responses of the monocyte cell line THP-1 were studied after challenge with three different MAP strains under standardized conditions. The bovine field isolate J1961 (major Type II) and the ovine field isolate JIII-86 (Type III) were compared with the laboratory adapted reference strain ATCC 19698 (Type II). Strains were shown by three different typing methods (IS900-RFLP-, MIRU-VNTR-, and SSR-analysis) to substantially differ in several genotypic features. Macrophage function was assessed by quantifying mRNA of the cytokines TNF-α, IL-1?, and IL-10 by quantitative RT-PCR. Secreted TNF-α protein was measured by a cytotoxicity test, IL-1? and IL-10 using ELISA tests. The three MAP strains of various genotypes differ in their effect on human macrophages depending on challenge dose and infection time. These differences concerned both the mRNA level and secreted protein amounts of proinflammatory cytokines TNF-α, IL-1β and anti-inflammatory cytokine IL-10. Type III strain produced less IL-10 and IL-1β mRNA and protein but more TNF-α protein at 2h than the Type II strains. In summary, our results support the hypothesis that strain characteristics might have relevance for the host response towards MAP and, consequently, for the pathogenesis of paratuberculosis.     

Resistenz des Bitterfäule-Erregers Neofabraea perennans gegen Thiophanate-methyl: Konidienkeimung vs. Hyphenwachstum

Isolates of Neofabraea perennans were grouped into three categories according to their pattern of resistance against thiophanate-methyl. ED₅₀ values were 0.067?±?0.003?ppm (mycelial growth) or 0.202?±?0.028?ppm (conidial germination) for strains with baseline sensitivity, and 1.35?±?0.30?ppm or 9.75?±?3.18?ppm (respectively) for strains with partial resistance against thiophanate-methyl. Highly resistant strains were not inhibited even at 400?ppm thiophanate-methyl. The mycelial growth assay is recommended for further research on benzimidazole resistance in bitter-rot fungi because of its enhanced sensitivity as well as simple and reproducible evaluation. A detailed protocol for this assay method is given.     

Endothelin receptor subtype A blockade does not affect the haemodynamic recovery from haemorrhage during xenon/remifentanil or isoflurane/remifentanil anaesthesia in dogs

ObjectiveTo test the compensatory role of endothelin-1 when acute blood loss is superimposed on anaesthesia, by characterizing the effect of systemic endothelin receptor subtype A (ET_A) blockade on the haemodynamic and hormonal responses to haemorrhage in dogs anaesthetized with xenon/remifentanil (X/R) or isoflurane/remifentanil (I/R).Study designProspective experimental randomized controlled study.AnimalsSix female Beagle dogs, 13.4 ± 1.3 kg.MethodsAnimals were anaesthetized with remifentanil 0.5 μg kg^?1 minute^?1 plus either 0.8% isoflurane (I/R) or 63% xenon (X/R), with and without (Control) the systemic intravenous endothelin receptor subtype A antagonist atrasentan (four groups, n = 6 each). After 60 minutes of baseline anaesthesia, the dogs were bled (20 mL kg^?1) over 5 minutes and hypovolemia was maintained for 1 hour. Continuous haemodynamic monitoring was performed via femoral and pulmonary artery catheters; vasoactive hormones were measured before and after haemorrhage.ResultsIn Controls, systemic vascular resistance (SVR), vasopressin and catecholamine plasma concentrations were higher with X/R than with I/R anaesthesia at pre-haemorrhage baseline. The peak increase after haemorrhage was higher during X/R than during I/R anaesthesia (SVR 7420 ± 867 versus 5423 ± 547 dyne seconds cm^?5; vasopressin 104 ± 23 versus 44 ± 6 pg mL^?1; epinephrine 2956 ± 310 versus 177 ± 99 pg mL^?1; norepinephrine 862 ± 117 versus 195 ± 33 pg mL^?1, p < 0.05). Haemorrhage reduced central venous pressure from 3 ± 1 to 1 ± 1 cmH₂O (I/R, ns) and from 8 ± 1 to 5 ± 1 cmH₂O (X/R, p < 0.05), but did not reduce mean arterial pressure, nor cardiac output. Atrasentan did not alter the haemodynamic and hormonal response to haemorrhage during either anaesthetic protocol.Conclusions and clinical relevanceSelective ET_A receptor blockade with atrasentan did not impair the haemodynamic and hormonal compensation of acute haemorrhage during X/R or I/R anaesthesia in dogs.     

Measuring nitrogen fixation by <Emphasis Type="Italic">Sesbania sesban</Emphasis> planted fallows using <Superscript>15</Superscript>N tracer technique in Kenya

A field experiment was performed in eastern Kenya to estimate N₂ fixation by Sesbania sesban over an 18-month period using the ¹⁵N dilution method. The influence of three reference species, Senna spectabilis, Eucalyptus saligna and Grevillea robusta, on the estimates of N₂ fixation was also assessed. Percentage Ndfa (nitrogen derived from the atmosphere) was calculated based on foliar atom excess (FAE), above-ground atom excess (AAE) or whole tree atom excess (WAE) data. The differences in atom% ¹⁵N excess values between species and plant parts are presented and discussed. We recommend the use of several reference species for estimating %Ndfa and that the different results obtained should be carefully considered in relation to the issues being addressed. In this study, Senna was the most suitable of the three reference species because its N uptake pattern and phenology were very similar to those of Sesbania. When well established, the amount of N fixed by Sesbania accounts for more than 80% of its total N content, according to FAE-based estimates. We estimated the Ndfa by Sesbania after 18 months to between 500 and 600 kg ha⁻¹ , depending on whether FAE, AAE or WAE data were used and on the choice of reference species. The substantial accumulation of N in planted Sesbania highlighted its potential to increase the sustainability of crop production on N-limited soils. We consider the ¹⁵N dilution method to be appropriate for quantifying N₂ fixation in improved fallows in studies, similar to this one, of young trees with high N₂-fixing ability.     

A strategy for tree-perennial crop productivity: nursery phase nutrient additions in cocoa-shade agroforestry systems

Shade tolerant species response to nutrient additions and light regulation by canopy trees in perennial agroforestry systems has been well documented. However, accelerated early growth, particularly in cocoa-shade systems, may be offset by competition for limited resources on nutrient poor sites. To date, few agroforestry management strategies focus on nutrient manipulation of the shade tree component or strategies for precision nutrient application. Our research objective was to diagnose interactions between nutrient supplied shade trees intercropped with cocoa. We established greenhouse trials in Kwadaso, Ghana cultivating Terminalia superba seedlings with four fertility treatment levels: conventional rate (current practices) under linear additions, and half, full and double conventional rate under exponential additions (steady-state nutrition) to determine maximal growth and nutrient uptake. After 4 months of additions in the nursery, pre-fertilized T. superba seedlings were then out-planted into field trials with cocoa seedlings. After 4 months of intercropping, cocoa associated with half rate exponentially supplied T. superba had significantly larger leaf area, greater leaf number, and higher nutrition (N and P uptake) than cocoa associated with full rate conventionally supplied T. superba. This may be attributed to (1) more favorable light conditions under these taller shade seedlings and (2) the internal use of nutrients associated with exponentially supplied T. superba seedlings, which lowered stress on native soil resources. The latter is corroborated with our findings on soil fertility status. This strategy focused on reducing fertilizer inputs and developing precise plant nutrition technology for on-farm use. Our findings suggest that shade seedlings under steady state nutrition can mitigate early growth competition in the field.     

Abundance and pest classification of scolytid species (Coleoptera: Curculionidae, Scolytinae) follow different patterns

Scolytids have been studied more than any other group of forest insects, but most investigations have been restricted to only a few pest species. This bias hampers our understanding of variation in abundance and pest status. Even the simple question whether the abundance of scolytids can predicted by the same independent variables as their pest status is still a matter of debate. To explore this issue, we estimated their abundance using non-attracting flight-interception traps set in a wide range of forests across Czech Republic, Germany, and France. Pest status was taken from current literature. As independent variables, we considered host range, host abundance, and several traits of the considered species in linear models using generalized least squares with a correlation structure derived from the phylogenetic tree of the beetles. Host range was calculated as the root phylogenetic diversity index. The variation in the abundance across scolytids was well explained by resource-related parameters (R² = 0.53). In contrast to abundance, the pest status was significantly related to species-specific traits, such as body size and maximum number of generations. However, the explained variance was much lower (R² = 0.19). Although our analysis showed that abundance and pest score follow different patterns, we stress the importance of monitoring all species using non-selective traps. Considering the increasing global trade and the rapidly changing climate, such a broad ecological monitoring is necessary to detect new interactions and/or invading species that may influence our forests ecosystems.     

Enhancing biological efficacy and rainfastness of foliar applied calcium chloride solutions by addition of rapeseedoil surfactants

The efficacy of a homologous series of biodegradable rapeseedoil derivatives (triglyceride ethoxylates; Agnique RSO® series, Cognis, Düsseldorf, Germany) with an average of 5, 10, 30, and 60 units of ethylene oxide (EO) as adjuvants for foliar‐applied calcium chloride (CaCl₂) was evaluated in Malus domestica L. Borkh. Previous experiments revealed that the surfactants used are not phytotoxic. All the surfactants applied decreased contact angles of spray solutions. The lipophilic surfactants RSO 5 and RSO 10 reduced contact angles more than the hydrophilic ones. Drying time of spray droplets was most prolonged when RSO 5 was added. Our data provide evidence that the most lipophilic surfactant RSO 5 can enhance Ca penetration, which was shown in isolated cuticles of tomato fruits (Lycopersicon esculentum cv. Panovy) as a model system. The surfactant effect was most pronounced during the first 4 h and reached a plateau after 24 h. Rainfastness of Ca on surfaces of Malus domestica leaves was improved when RSO 5 was added to CaCl₂ spray solutions. All surfactants applied improved rainfastness of Ca on ’︁Braeburn’ fruit surfaces compared to the treatment with CaCl₂ alone. Under field conditions, leaf/fruit application of CaCl₂/RSO 5 led to an increased Ca content in ’︁Braeburn’ apple fruits and a reduced bitter pit incidence.     

Estimation and economic evaluation of aboveground carbon storage of <Emphasis Type="Italic">Tectona grandis</Emphasis> plantations in Western Panama

Tropical tree plantations may play an important role in mitigating CO₂ emissions through their potential to capture and sequester carbon from the atmosphere. The Clean Development Mechanism (CDM) as well as voluntary initiatives provide economic incentives for afforestation and reforestation efforts through the generation and sale of carbon credits. The objectives of our study were to measure the carbon (C) storage potential of 1, 2 and 10-years old Tectona grandis plantations in the province of Chiriquí, Western Panama and to calculate the monetary value of aboveground C storage if sold as Certified Emission Reduction (CER) carbon credits. The average aboveground C storage ranged from 2.9 Mg C ha⁻¹ in the 1-year-old plantations to 40.7 Mg C ha⁻¹ in the 10-year-old plantations. Using regression analysis we estimated the potential aboveground C storage of the teak plantation over a 20 year rotation period. The CO₂-storage over this period amounted to 191.1 Mg CO₂ ha⁻¹. The discounted revenues that could be obtained by issuance of carbon credits during a 20 year rotation period were about US$460 for temporary CER and US$560 for long-term CER, and thus, contribute to a minor extent (1%) to overall revenues, only.     

Arthropod species richness in the Norway Spruce (Picea abies (L.) Karst.) canopy along an elevation gradient

Norway Spruce is the economically most important tree species in Europe and has been cultivated in plantations on a large-scale at low elevations, far outside its natural range. In the Bohemian Forest, it naturally occurs in pure stands above 1150 m a.s.l. and as a mixed tree species from 650 to 1150 m a.s.l. An understanding of natural distributions and the diversity along temperature gradients at various elevations is important for conservation, pest management, and predictions of future species assemblages by global warming. Here we investigated the species richness of canopy arthropods in spruce trees along a gradient from 300 to 1300 m a.s.l. using flight-interception traps. We analyzed species richness by combining diversity partitioning with a moving window approach after standardizing sample size per plot. Total richness decreased linearly as the elevation increased, which reflected declining temperatures and a declining regional species pool. Phytophages (herbivores excluding xylophages) were the most influenced. Richness did not peak at the transition zones of the three ecological elevation zones, neither for all species, nor for any of the separate functional groups. However, the proportion of both beetle and true bug spruce specialists significantly increased with elevation and actually doubled in richness above 1000 m a.s.l., where spruce is naturally dominating. Our results indicate that even planted spruce trees at lower elevations maintain high levels of species richness. Further climate warming will promote overall species richness, especially of phytophages, at all elevations. However, spruce specialists may be seriously threatened by global warming.