Contribution of the life-history traits of a plant pathogen to the development of field epidemics

The pathogenicity-related traits of biotrophic plant pathogens are usually measured on the individual host plant, at the scale of a single pathogen life cycle, whereas epidemic development in the field encompasses a succession of cycles. It remains unclear which traits make the greatest contribution to pathogen fitness in the field and to epidemic severity. The objective of this study was to determine the contributions of elementary pathogenicity traits to epidemic development in field conditions. We challenged a set of wheat cultivars with three different leaf rust isolates, under both controlled and field conditions, in 3 consecutive years. Infection efficiency, latent period, lesion size, spore production per lesion and spore production capacity were measured in the greenhouse, whereas disease severity was measured in the field. Most, but not all, of the pathogenicity traits were related to each other. All traits contributed to epidemic development in the field, but to different extents. Surprisingly, lesion size and spore production per lesion were inversely correlated with epidemic severity. Conversely, there was a strong positive correlation between spore production capacity and pathogen fitness in the field, in accordance with the concept of propagule pressure as a strong determinant of invasion success. Severe epidemics were mostly associated with small lesions with a high spore production capacity, high infection efficiency and a short latent period.     

Assessment of selenium bioavailability from high-selenium spirulina subfractions in selenium-deficient rats

It was previously found that the bioavailability of Se from Se-rich spirulina (SeSp) was lower than that from selenite or selenomethionine when fed to Se-deficient rats. The present study examined the bioavailability of Se from SeSp subfractions: a pellet (P) issuing from the centrifugation of a suspension of broken SeSp and a retentate (R) resulting from ultrafiltration of the supernatant through a 30 kDa exclusion membrane. Animals were fed a torula yeast based diet with no Se (deficients) or supplemented with 75 microg of Se/kg of diet as sodium selenite (controls) for 42 days. Se-deficient rats were then repleted for 56 days with Se (75 microg/kg of diet) supplied as sodium selenite, SeSp, P, or R. During this period, controls continued to receive sodium selenite. Speciation of Se in subfractions showed that the majority was present in the form of high molecular weight compounds; free selenomethionine was only a minor constituent. Gross absorption of Se from sodium selenite, P, and R was not different and was higher than from SeSp. Only retentate allowed full replenishment of Se concentration in liver and kidney (as did sodium selenite) and glutathione peroxidase (GSHPx) activity in liver, kidney, plasma, and erythrocytes. The bioavailabilities of Se in retentate, as assessed by slope ratio analysis using selenite as a reference Se, were 89 and 112% in the tissue Se content and 106-133% in the GSHPx activities. SeSp and P exhibited a gross bioavailability of <100%. These results indicate that Se in retentate is highly bioavailable and represents an interesting source of Se for food supplementation.     

Biodiversity of Fusarium species in ears and stalks of maize plants in Belgium

In order to investigate the pre-harvest contamination of maize plants by Fusarium species in Belgium, a three-year survey has been performed in five fields in which three hybrids differing in susceptibility to maize stalk rot were sampled at four different physiological stages. An extensive collection of 5,659 Fusarium isolates characterized at the species level was established during the 2005, 2006, and 2007 growing seasons, with a total of 23 different Fusarium species identified to occur on ears and stalks. A high number of plants was already contaminated by Fusarium spp. at the anthesis stage, although no symptoms were visible on ears or on stalks. As the season progressed, the incidence of Fusarium-infected maize plants reached 100% in several fields. At the end of the growing season, the most frequently isolated species in maize ears were F. graminearum, sometimes associated with F. avenaceum, F. crookwellense, F. culmorum, F. poae, and F. temperatum, a new species recently described on maize. The predominant Fusarium species detected in stalks at the end of the growing season were F. graminearum and F. crookwellense, often associated with F. culmorum and F. temperatum. Year-to-year variability observed for the incidence of F. graminearum can most likely be associated with differences in climatic conditions among the three years.     

Synthesis and sensorial properties of 2-alkylalk-2-enals and 3-(acetylthio)-2-alkyl alkanals

Parallel synthesis was applied to prepare a series of 3-(acetylthio)-2-alkyl alkanals by Michael addition of thioacetic acid under alkaline conditions to alpha,beta-unsaturated 2-alkyl-substituted aldehydes, which were obtained by aldol condensation of the corresponding primary aldehydes as starting materials. The target compounds were characterized in terms of GC, MS, and NMR data. The sensory properties of the odorants, such as odor quality and odor detection threshold value, were determined with a trained panel. Structure-activity relationships are discussed, suggesting that the 1,3-oxygen-sulfur functionality, required for the "olfactophore" of tropical/vegetable notes, can further be extended to the acetylthio derivatives.     

Generating optical Schrödinger kittens for quantum information processing

We present a detailed experimental analysis of a free-propagating light pulse prepared in a "Schr?dinger kitten" state, which is defined as a quantum superposition of "classical" coherent states with small amplitudes. This kitten state is generated by subtracting one photon from a squeezed vacuum beam, and it clearly presents a negative Wigner function. The predicted influence of the experimental parameters is in excellent agreement with the experimental results. The amplitude of the coherent states can be amplified to transform our "Schr?dinger kittens" into bigger Schr?dinger cats, providing an essential tool for quantum information processing.     

Impact of toasting oak barrels on the presence of polycyclic aromatic hydrocarbons in wine

Toasting Quercus sp. oak wood is one of the key stages in manufacturing barrels intended for aging wines and spirits. During this operation, the increase in temperature causes variable modifications in the physical structure and, more importantly, the chemical composition of the wood. Polycyclic aromatic hydrocarbons (PAH) are high-risk molecules likely to be formed during toasting of the wood and later extracted by wine or spirits in direct contact with the barrel. In the context of an analysis of all potential sources of risk associated with the manufacture of barrels for winery use [prevention policy defined using a Hazard Analysis Critical Control Point (HACCP) approach], we carried out a preliminary study to provide a more accurate assessment of potential risks related to the presence of PAH in cooperage and winemaking. Wood toasted to different levels under different conditions, as well as wines aged in barrels made using different methods, was analyzed by gas chromatography and mass spectrometry (GC-MS) for the identification of the main PAH present, quantification of each of the molecules extracted, and estimation of any possible toxicological risks, via a comparison of values with those measured in other types of food. The results clearly showed that the heating processes associated with barrel production actually resulted in the formation of various molecules in the PAH family. However, only a minority of the target PAH presented high toxicity, particularly carcinogenic potential. Because of the specific toasting process used, benzo[a]pyrene, the best-known, and one of the most dangerous, contaminants, was not significantly present in toasted barrel wood. In view of the PAH concentrations in wood and the low solubility of these compounds, their extraction in wine is apparently relatively slow and limited. Finally, comparing the overall PAH concentrations, and particularly those of the most toxic compounds, with estimated absorption from food or the environment, we found it was obvious that the contribution of toasted barrels to the total amount was extremely low and should not, therefore, be considered a major health concern.     

Glycosylations of kappa-casein-derived caseinomacropeptide reduce its accessibility to endo- but not exointestinal brush border membrane peptidases

Caseinomacropeptide (CMP) is a peptide obtained from kappa-casein hydrolysis by gastric proteinases and which exhibits various biological activities. The aim of this study was to analyze the intestinal processing of CMP at the brush border membrane (BBM) level. Intestinal BBM vesicles (BBMV) were used to digest glycosylated and unglycosylated CMP. Our results demonstrated that whatever was the glycosylated state of CMP, they were digested by BBMV intestinal enzymes, from macropeptides to free amino acids. The digestion of unglycosylated and glycosylated CMP throughout the action of exopeptidases was similar, but the activity of endopeptideases on glycosylated CMP was limited, certainly due to the attached O-glycosylations. Consequently, much more peptides were identified from the unglycosylated than from the glycosylated CMP. In addition, the glycosylation core as well as the number of the attached glycosylated chain modified the kinetic of digestion; the most heavily glycosylated forms being the slowest digested.     

Dynamic multistate site occupancy models to evaluate hypotheses relevant to conservation of Golden Eagles in Denali National Park, Alaska

The recent development of multistate site occupancy models offers great opportunities to frame and solve decision problems for conservation that can be viewed in terms of site occupancy. These models have several characteristics (e.g., they account for detectability) that make them particularly well suited for addressing management and conservation problems. We applied multistate site occupancy models to evaluate hypotheses related to the conservation and management of Golden Eagles (Aquila chrysaetos) in Denali National Park, Alaska, and provided estimates of transition probabilities among three occupancy states for nesting areas (occupied with successful reproduction, occupied with unsuccessful reproduction, and unoccupied). Our estimation models included the effect of potential recreational activities (hikers) and environmental covariates such as a snowshoe hare (Lepus americanus) index on transition probabilities among the three occupancy states. Based on the most parsimonious model, support for the hypothesis of an effect of potential human disturbance on site occupancy dynamics was equivocal. There was some evidence that potential human disturbance negatively affected local colonization of territories, but there was no evidence of an effect on reproductive performance parameters. In addition, models that assume a positive relationship between the hare index and successful reproduction were well supported by the data. The statistical approach that we used is particularly useful to parameterize management models that can then be used to make optimal decisions related to the management of Golden Eagles in Denali. Although in our case we were particularly interested in managing recreational activities, we believe that such models should be useful to for a broad class of management and conservation problems.