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Soil nematodes are both taxonomically and functionally diverse, respond quickly to soil perturbation and have much potential as indicators of soil health. However, because of the perceived difficulty of identifying nematodes to species level morphologically, they are frequently neglected in soil ecological studies. Recently, extraction of soil DNA, amplification of 18S rDNA genes using nematode consensus primers and subsequent separation by denaturing gradient gel electrophoresis (DGGE) has been used to estimate nematode diversity in soil. Here, we investigate an alternative approach whereby nematodes are first extracted from the soil prior the 18S rDNA gene amplification using universal primers. We used this system to estimate nematode species richness in 10 soil samples—five from Scotland and five from the Netherlands. There was no direct correlation between species richness as estimated morphologically and by the PCR-DGGE method. However, inspection of the data suggested that the samples fell into two discrete groups, which was confirmed by canonical and stepwise discriminant function analysis; the values for the Shannon and equitability indices being important discriminators. Further analysis revealed a significant relationship between morphological species richness and DGGE estimates for species that represented greater than 1% of the sample biomass. 相似文献
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Marianne Le Bail Marie-Hlne Jeuffroy Christine Bouchard Aude Barbottin 《European Journal of Agronomy》2005,23(4):379-391
To optimize wheat segregation for the various markets, it is necessary to add to genotype segregation, a prediction before harvest of the values of yield and grain protein concentration (GPC) for the different fields of the collecting area. Different tools allowing a prediction of crop production exist. Among them, the evaluation of nitrogen concentration by a chlorophyll meter (Soil–Plant Analysis Development (SPAD) readings), classically used to adapt the nitrogen fertilizer application, has been used in few works to foresee grain yield and grain protein concentration. But the relationships between N crop status and SPAD measurements varies among varieties and this genotypic effect has rarely been incorporated in models of forecasting grain quality.
This paper compares several models to forecast yield, nitrogen uptake in grain (NUG) and grain protein concentration from trials carried out in 2001 and 2002 at the INRA experiment station of Grignon (West of Paris). Trials crossed nine varieties by four (2002) or five (2001) nitrogen rates. Input variables of those models are mainly chlorophyll meter measurements (SPAD) on the penultimate leaf at GS65 and on the flag leaf at GS71 Zadoks growth stages and ear number per square meter (NE).
A square root model of yield based on NE × SPAD gave the best fit (RMSE = 0.6 t ha−1 for both stages) if considering three different groups of genotypes. Based on the same variable, NE × SPAD, a quadratic model for NUG without significant effect of genotypes gave the best fit (RMSE, between 21 and 30 kg ha−1 depending of the growth stage). And, for GPC, considering the same three groups of genotypes, the slope of the linear model with the ratio of predicted grain nitrogen concentration to predicted yield, is the same at both stages and very close to the standard value used to calculate protein concentration from nitrogen concentration (5.7), but the predictive quality of the model is more than 10% higher at GS71 (R2 of 0.77) than at flowering (R2 of 0.64). Finally, the sensibility of the models to delay in the stage of measurement is discussed. 相似文献
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Maria Martoub Aude Couty Philippe Giordanengo Arnaud Ameline 《Journal of pest science》2011,84(2):229-233
Mineral oil has been considered for several decades as an effective mean to control aphids and reduce the spread of non-persistent
viruses. Mineral oil seems to reduce virus transmission efficiency interfering with the binding of the virions in the aphid
stylets. However, several studies have shown the possible disruption of host selection process by mineral oil and some works
have demonstrated a direct effect on the aphid vector. In this study the insecticidal properties of mineral oil (Finavestan
EMA) alone against Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae) were evaluated through the three main routes of exposure (topical contact, inhalation and
ingestion). Results showed that no aphid survived after topical contact at oil concentrations ranging from 3 to 100% v/v.
However, surprisingly, at a lower concentration (0.3%), survival was not affected but fecundity was enhanced. Moreover, exposure
to oil volatiles enhanced aphid survival at the highest concentrations (30 and 100%) and daily fecundity at the lowest ones
(0.3 and 3%). Delivered via artificial diet, mineral oil only affected aphid survival at the 0.3% concentration. This study
demonstrates that mineral oil alone, regardless of a potential plant effect can induce either probiotic effects or toxic effects,
depending on the mode of application and the concentration tested. These results can be of significance for the understanding
of mineral oil properties in the fields. 相似文献
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Marangon M Sauvage FX Waters EJ Vernhet A 《Journal of agricultural and food chemistry》2011,59(6):2652-2662
Consumers expect white wines to be clear. During the storage of wines, grape proteins can aggregate to form haze. These proteins, particularly chitinases and thaumatin-like proteins (TL-proteins), need to be removed, and this is done through adsorption by bentonite, an effective but inefficient wine-processing step. Alternative processes are sought, but, for them to be successful, an in-depth understanding of the causes of protein hazing is required. This study investigated the role played by ionic strength (I) and sulfate toward the aggregation of TL-proteins and chitinases upon heating. Purified proteins were dissolved in model wine and analyzed by dynamic light scattering (DLS). The effect of I on protein aggregation was investigated within the range from 2 to 500 mM/L. For chitinases, aggregation occurred during heating with I values of 100 and 500 mM/L, depending on the isoform. This aggregation immediately led to the formation of large particles (3 μm, visible haze after cooling). TL-protein aggregation was observed only with I of 500 mM/L; it mainly developed during cooling and led to the formation of finite aggregates (400 nm) that remained invisible. With sulfate in the medium chitinases formed visible haze immediately when heat was applied, whereas TL-proteins aggregated during cooling but not into particles large enough to be visible to the naked eye. The data show that the aggregation mechanisms of TL-proteins and chitinases are different and are influenced by the ionic strength and ionic content of the model wine. Under the conditions used in this study, chitinases were more prone to precipitate and form haze than TL-proteins. 相似文献
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Dufrechou M Poncet-Legrand C Sauvage FX Vernhet A 《Journal of agricultural and food chemistry》2012,60(5):1308-1319
Protein haze development in white wines is an unacceptable visual defect attributed to slow protein unfolding and aggregation. It is favored by wine exposure to excessive temperatures but can also develop in properly stored wines. In this study, the combined impact of pH (2.5-4.0), ionic strength (0.02-0.15 M), and temperature (25, 40, and 70 °C) on wine protein stability was investigated. The results showed three classes of proteins with low conformational stability involved in aggregation at room temperature: β-glucanases, chitinases, and some thaumatin-like protein isoforms (22-24 kDa). Unexpectedly, at 25 °C, maximum instability was observed at the lower pH, far from the protein isoelectric point. Increasing temperatures led to a shift of the maximum haze at higher pH. These different behaviors could be explained by the opposite impact of pH on intramolecular (conformational stability) and intermolecular (colloidal stability) electrostatic interactions. The present results highlight that wine pH and ionic strength play a determinant part in aggregation mechanisms, aggregate characteristics, and final haze. 相似文献
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C Le Bourvellec AA Watrelot C Ginies A Imberty CM Renard 《Journal of agricultural and food chemistry》2012,60(37):9484-9494
Procyanidins can bind cell wall material in raw product, and it could be supposed that the same mechanism of retention of procyanidins by apple cell walls takes place in cooked products. To evaluate the influence of cell wall composition and disassembly during cooking on the cell walls' capacity to interact with procyanidins, four cell wall materials differing in their protein contents and physical characteristics were prepared: cell wall with proteins, cell wall devoid of protein, and two processed cell walls differing by their drying method. Protein contents varied from 23 to 99 mg/g and surface areas from 1.26 to 3.16 m(2)/g. Apple procyanidins with an average polymerization degree of 8.7 were used. The adsorption of apple procyanidins on solid cell wall material was quantified using the Langmuir isotherm formulation. The protein contents in cell wall material had no effect on procyanidin/cell wall interactions, whereas modification of the cell wall material by boiling, which reduces pectin content, and drying decreased the apparent affinity and increased the apparent saturation levels when constants were expressed relative to cell wall weight. However, boiling and drying increased apparent saturation levels and had no effect on apparent affinity when the same data were expressed per surface units. Isothermal titration calorimetry indicated strong affinity (K(a) = 1.4 × 10(4) M(-1)) between pectins solubilized by boiling and procyanidins. This study higllights the impact of highly methylated pectins and drying, that is, composition and structure of cell wall in the cell wall/procyanidin interactions. 相似文献
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Aude Ernoult Yves Tremauville Pierre Margerie Didier Alard 《Biological conservation》2006,127(1):1-17
Changes in landscape pattern under the control of agriculture intensification are considered to be an important driver of biodiversity and often a threat for conservation. The response of species to landscape changes is complex, including possible time lags, and depends on the taxonomic group. The search for surrogate species or surrogate data for biodiversity is confronted with this complexity.This study was conducted on two taxonomic groups (birds and vascular plants) for 20 sites each of 1 km2 equally distributed in the Seine valley floodplain. For plants, two habitats were studied: grasslands and hedges. We used a generalised additive model (GAM) and co-inertia analyses to determine whether present or past landscape attributes can best explain the biodiversity components (structure and composition). This study confirms the major role of landscape pattern attributes for predicting some metrics of biodiversity, e.g. species richness. But this study shows that potential drivers of biodiversity come from both the past and present landscape patterns. The quality of surrogates for biodiversity is strongly dependent on understanding the importance of past conditions. This suggests the need for more functional surrogates, taking into account the situation of equilibrium or non-equilibrium between biodiversity and its drivers. 相似文献