The genome of the diatom Thalassiosira pseudonana: ecology, evolution, and metabolism

Diatoms are unicellular algae with plastids acquired by secondary endosymbiosis. They are responsible for approximately 20% of global carbon fixation. We report the 34 million-base pair draft nuclear genome of the marine diatom Thalassiosira pseudonana and its 129 thousand-base pair plastid and 44 thousand-base pair mitochondrial genomes. Sequence and optical restriction mapping revealed 24 diploid nuclear chromosomes. We identified novel genes for silicic acid transport and formation of silica-based cell walls, high-affinity iron uptake, biosynthetic enzymes for several types of polyunsaturated fatty acids, use of a range of nitrogenous compounds, and a complete urea cycle, all attributes that allow diatoms to prosper in aquatic environments.     

Measuring Eastern Redcedar (Juniperus virginiana L.) Mass With the Use of Satellite Imagery

Eastern redcedar (Juniperus virginiana L.) is an aggressively spreading native species in Oklahoma grasslands. It decreases rangeland forage production, and has been implicated in reducing stream flow and groundwater recharge. Industrial-scale plans to use redcedar as a biofuel source are being considered. Optimal placement of redcedar-based industries requires determination of redcedar availability. Such large-area inventories of redcedar mass can be practically addressed via aircraft or satellite remote sensing. Therefore, we conducted a study in central and western Oklahoma to develop and test a remote-sensing–based allometric equation relating redcedar canopy area to aboveground dry mass (AGM). We used automated methods to measure tree canopy area from georectified, pan-sharpened, multispectral QuickBird images having a spatial resolution of 0. 45 m² per pixel ground sample area. We also measured the canopy area and fresh and dry mass of these trees with the use of destructive sampling techniques. Regression analysis showed that satellite-derived measurements of canopy coverage explained about 85% of field-measured redcedar dry AGM in the study plots. The resulting allometric equation was applied to an independent data set, yielding dry AGM of 38.2 metric tons ? ha^?1, which was well within the field-measured range of 36–43 metric tons ? ha^?1. The allometric equation was then applied to Natural Resources Conservation Service measurements of redcedar canopy coverage for 17 counties in Oklahoma, to determine that the area of interest contains a median value of about 11.5 million metric tons of redcedar AGM. These results indicate that 0.45-m² spatial resolution multispectral imagery can be a useful tool for rapid and reliable measurement of redcedar dry AGM.     

Derivation and testing of a model to predict selection for fungicide resistance

A mathematical model was derived to predict selection for fungicide resistance in foliar pathogens of cereal crops. The model was tested against independent data from four field experiments quantifying selection for the G143A mutation conferring resistance to a quinone outside inhibitor (QoI) fungicide in powdery mildew (Blumeria graminis f.sp. hordei) on spring barley (Hordeum vulgare). Fungicide treatments with azoxystrobin differed in the total applied dose and spray number. For each treatment, we calculated the observed selection ratio as the ratio of the frequency of the resistant strain after the last and before the first spray. The model accurately predicted the variation in observed selection ratios with total applied fungicide dose and number of sprays for three of the four experiments. Underprediction of selection ratios in one experiment was attributed to the particularly late epidemic onset in that experiment. When the equation representing epidemic development was modified to account for the late epidemic, predicted and observed selection ratios at that site were in close agreement. On a scatter plot of observed selection ratios on predicted selection ratios, for all four experiments, the 1:1 line explained 89–92% of the variance in the mean of observed selection ratios. To our knowledge, this is the first fungicide resistance model for plant pathogens to be rigorously tested against field data. The model can be used with some degree of confidence, to identify anti‐resistance treatment strategies which are likely to be effective and would justify the resources required for experimental testing.     

Effect of host and inoculum patterns on take-all disease of wheat incidence,severity and disease gradient

The importance of the spatial aspect of epidemics has been recognized from the outset of plant disease epidemiology. The objective of this study was to determine if the host spatial structure influenced the spatio-temporal development of take-all disease of wheat, depending on the inoculum spatial structure. Three sowing patterns of wheat (broadcast sowing, line sowing and sowing in hills) and three patterns of inoculum (uniform, aggregated and natural infestation) were tested in a field experiment, repeated over 2 years. Disease (severity, root disease incidence, plant disease incidence and, when applicable, line and hill incidences) was assessed seven times during the course of each season and the spatial pattern was characterized with incidence-incidence relationships. In the naturally infested plots, disease levels at all measurement scales were significantly higher in plots sown in hills, compared to plots sown in line, which were in turn significantly more diseased than plots with broadcast sowing. Disease aggregation within roots and plants was stronger in line and hill sowing than in broadcast sowing. Analysis of the disease gradient in the artificially infested plots showed that the disease intensified (local increase of disease level) more than it extensified (spatial spread of the disease), the effect of the introduced inoculum was reduced by 95% at a distance of 15 cm away from the point of infestation. Yield was not significantly affected by sowing pattern or artificial infestation.     

Production, purification, and properties of an endoglucanase produced by the hyphomycete Chalara (Syn. Thielaviopsis) paradoxa CH32

The hyphomycete Chalara (syn. Thielaviopsis) paradoxa produces endoglucanase activity during the late trophophase. The low molecular mass (35 kDa) endoglucanase purified from cultured broths works optimally at 37 degrees C and pH 5.0. The enzyme inactivates at pH below 3.0 and also at temperatures of 50 degrees C or higher, but it is stable at lower temperatures, including refrigeration temperature and freezing. The enzyme is inhibited by detergents, by EDTA, and by the divalent cations Hg(2+) and Ag(2+). It is also inhibited to some extent by 10 mM Zn(2+), Fe(2+), and Mg(2+), but it is stimulated by Mn(2+). Enzyme activity is not affected by reducing agents. In the presence of low concentrations of water miscible organic solvents (20%) endoglucanase activity is inhibited by 7% (for methanol) to 50% (for acetonitrile), and it is totally inhibited at higher solvent concentrations (50%). Enzyme activity is not affected by the water immiscible solvent ethyl acetate. Carboxymethylcellulose is the preferred substrate (K(m(app)) = 8.3 g/L; V(max(app)) = 1.1 microM/min). Hydrolysis of crystalline cellulosic substrates is very limited, but it is greatly enhanced by phosphoric acid swelling. The purified enzyme shows no activity toward disaccharides or aryl-glucosides. Its activity is inhibited by cellobiose.     

Improving minimum detectable differences in the assessment of soil organic matter change in short‐term field experiments

The demand for information on cropping system impact on soil organic matter (SOM) calls for efforts to improve the utilization of short‐term field experiments (e.g., to evaluate the parameterization of cropping systems in models). Those approaches have coped with the problem of determining small SOM changes within a large background mass. Thus, objectives of this survey are (1) the improvement of the minimum detectable difference (MDD) in SOM in the hudycrop short‐term field experiment by methods of sampling design and data treatment, (2) the verification to what extend the hudycrop short‐term field experiment allows for the determination of management induced effects on SOM, and (3) the investigation to what extent the obtained results may be suitable to evaluate the parameterization of a SOM balance model. The design of the hudycrop is suitable for excluding outliers plotwise. The estimation of plot means can be improved by the sampling design. Instead of determining a single plot mean in a mixed sampling procedure, the design provides multiple values for each plot, allowing for the identification of extreme values before calculating plot means. In consequence, minimum detectable differences decrease by a factor of 0.53 for soil organic C (SOC) and 0.63 for soil total N (STN) masses, allowing for detection of changes in the magnitude of 3.7 and 2.6% of background SOC and STN levels, respectively. Differences between treatments, however, are significant with corrected values (after outlier exclusion) for the crop production systems with the highest impact (potatoes and mulched red clover). Determining outliers based on Student's t‐test gives the lowest MDD and is therefore considered to be the most suitable method in this case. Correlations between apparent changes and SOM balances according to the HU‐MOD–2 model, used in this survey, indicate that the experimental design, in principal, is suitable for the evaluation of the parameterization of crop production systems in models. Still, an improved precision in SOM change detection is necessary. Reasonable options for that purpose are discussed in the paper.     

To compare the incubation period following intratracheal and subcutaneous inoculation of bovine leukosis virus infected lymphocytes and to study their clearance from the circulation

The migration of fluorescein isothiocyanate labelled lymphocytes through the tracheobronchial mucosa has been studied in cattle. Following intratracheal inoculation of labelled non-infected autologous lymphocytes and bovine leukosis virus (BLV) infected heterologous (presumed allogeneic) lymphocytes, the labelled lymphocytes appeared in the blood circulation between 4 and 7 days post inoculation. Following intravenous inoculation of labelled autologous lymphocytes, the cells could be detected in the circulation for 10 days post inoculation whereas BLV infected and non-infected heterologous lymphocytes could be detected for only 2 days. The migration of BLV-infected heterologous lymphocytes through the tracheobronchial mucosa caused a delay in the appearance of labelled lymphocytes in the circulation and a corresponding delay in the appearance of BLV antibodies. Comparison was made of the effect of two different routes of inoculation, subcutaneous and intratracheal on the incubation period as indicated by the detection of antibody. Subcutaneous inoculation of 1 X 10(4), 5 X 10(3), 1 X 10(3) of lymphocytes from a BLV infected cow caused seroconversion whereas 5 X 10(2) cells did not. Intratracheal inoculation of 5 X 10(3) cells caused sero-conversion. One animal did not develop BLV antibody until 30 weeks after inoculation although BLV could be isolated from the blood at 24 and 26 weeks post inoculation.     

Protection against bovine leukosis virus infection in sheep with the BL 20 bovine lymphoblastoid cell line

The bovine lymphoblastoid BL 20 cell line derived from a case of sporadic bovine leukosis when inoculated into sheep did not induce an antibody response directed against bovine leukosis virus (BLV) structural proteins. Sheep were inoculated twice with the BL 20 cell line and then challenged with BLV infected lymphocytes. Three out of four sheep challenged four weeks after BL 20 inoculation did not develop BLV antibodies. Of the 12 sheep challenged later, three sheep did not develop BLV antibodies. BLV was isolated from all the seropositive animals and from none of the seronegative animals.     

Effect of salicylates on intestinal secretion in calves given (intestinal loops) Escherichia coli heat-stable enterotoxin

The inhibitory effect of salicylates on intestinal secretion in 1- to 5-day-old calves given Escherichia coli heat-stable enterotoxin (ST)-induced intestinal fluid response was investigated. Purified ST was diluted in isotonic saline solution to obtain 1:10, 1:25, 1:50, 1:75, and 1:100 dilutions. Each dilution (1 ml) was inoculated into ligated loops in the distal part of the jejunum of each calf. Acetylsalicylic acid (aspirin) given orally (100 mg/kg) at 4 hours before ST was inoculated did not substantially alter the intestinal fluid response to ST. Sodium salicylate (IV) infusion, begun simultaneously when, or at 1 hour after, ST was inoculated, significantly (P less than 0.05) decreased fluid accumulation in those loops inoculated with ST dilutions of 1:25 or greater. The sodium and potassium concentrations of the accumulated fluid did not differ significantly between or within treatment groups. These results indicate that sodium salicylate infusion may be beneficial in treating enterotoxic colibacillosis in calves. Aspirin given orally at the dose used in the present study, would not have any beneficial effect.