The detection of snail host habitats in liver fluke infected farms by use of plant indicators

Field investigations in 361 liver fluke infected cattle- or sheep-breeding farms on acid soil were carried out during thirty years in March and April to record indicator plants in relation to the category of site colonized by the intermediate host of liver fluke, the snail Galba truncatula. Seven types of snail zones and six species of indicator plants were recorded in the 7709 positive sites studied. The most frequent habitats were located at the peripheral extremities of open drainage furrows. Juncus acutiflorus, Juncus effusus, Glyceria fluitans, and Agrostis stolonifera were the indicator plants. Plant indicators were highly efficient (38-80% of variance explained) when used with the size of site area within a hydrographical zone. The identification of positive sites for G. truncatula is a key for controlling the intermediate host on pastures through biological control with predatory molluscs. The positive sites may be detected using a two-step method including first categorization of hydrographical zones and then, within a zone, use of one or several indicator plants (frequently J. acutiflorus).     

Zur Bedeutung des Aggregierungsgrades für die Spannungsverteilung in strukturierten Böden

The effect of soil aggregation on stress distribution in structured soils The mechanical compressibility of arable soils can be described by preconsolidation load value and by the shear resistance parameters of the bulk soil and single aggregates. In order to quantify the effective stress equation must be also known the hydraulic properties of the soil in dependence of the intensity, kind, and number of loading events. The soil reacts as a rigid body at very fast wheeling speed inclusive a very pronounced stress attenuation in the top soil while stresses will be distributed in the soil threedimensionally to deeper depths at slower speed. These variations can be explained by the mechanical as well as by the hydraulic parameters of the bulk soil and single aggregates. Thus, the pore water pressure value of the bulk soil as a parameter of the effective stress equation further depends on the hydraulic properties of the inter- and intraaggregate pore system and continuity. As can be derived from the results the pore water pressure values are identical irrespective of the predessication for clayey polyhedres at high load while in coarse textured prisms the pore water pressure value depends on load and predryness. The consequences for soil strength under dynamic loading are shortly discussed.     

Isozyme polymorphism and geographic differentiation in a collection of French perennial ryegrass populations

Summary A sample of 60 natural populations of perennial ryegrass from France has been studied for allelic variation at 7 polymorphic enzyme loci. Population genetic statistics are of the same magnitude than those previously reported for other outbreeding, short-lived perennial species (P = 64%, A = 2.75, H = 0.270).Genotype frequencies at most collection sites do not deviate significantly from Hardy-Weinberg expectations, with however a slight deficit of heterozygotes which may be accounted for by a Wahlund effect. Gene diversity is mainly explained by the within population component. The between population differentiation F_st averaged on 4 loci is only 0.054, which accounts for only 6% of the whole diversity.When mapped, most allele frequencies do not show any special structure. Only five alleles present a clinal trend from North to South. These 5 alleles are probably related to some climatic factors such as average temperature or potential evapotranspiration. The causal hypotheses about the low level of between-population differentiation and spatial structure are discussed with reference to the literature.The consequences of the found population structure for sampling and conservation strategies of natural populations for genetic resources are presented and discussed.     

Cell neutrality in sodium chloride‐treated leaves and calli of the wilty mutant lycopersicon esculentum flacca and the wild species lycopersicon peruvianum

Some parameters involved in cell neutrality (inorganic solute, cation‐anion balance, proline and organic acid contents linked to oxidative respiration, and PEPCase activity) were determined in salinized plant leaves and leaf calli from two tomato species, the wilty mutant Lycopersicon esculentum cv flacca, and the wild relative L. peruvianum. Callus sensitivity was associated to membrane integrity and cell neutrality; while whole plant sensitivity was linked to nutritional unbalance and energy supply, both factors affecting the maintenance of the cell neutrality by means of ion translocation/compartimentalization.     

Comparable sensitivity and specificity in three commercially available ELISAs to differentiate between cattle infected with or vaccinated against foot-and-mouth disease virus

Three commercially available ELISAs for the detection of antibodies to the non-structural proteins of foot-and-mouth disease virus (FMDV) were evaluated, using sera from uninfected, vaccinated, infected, inoculated, first vaccinated and subsequently infected, and first vaccinated and subsequently inoculated cattle. We compared antibody kinetics to non-structural proteins, sensitivity, and specificity. One of the ELISAs had a higher sensitivity and much lower specificity than the other two, therefore we established standardised cutoff values for the compared assays using receiver operated characteristic (ROC) curves. Using the standardised cutoff values, all three ELISAs produced comparable results with respect to sensitivity and specificity. Antibody development to non-structural proteins after infection and after vaccination/infection was not significantly different. Development of antibodies, however, both neutralising and directed to non-structural proteins, was significantly delayed after intranasal inoculation as compared to intradermolingual infection. Based on results of sera obtained after vaccination and experimental infection all three assays can be used for testing sera collected between 4 weeks and 6 months after infection. More information is needed on the prevalence of positive reactors in a situation where emergency vaccination has been used and FMD transmission was still observed.     

Registration of visible and near infrared unmanned aerial vehicle images based on Fourier-Mellin transform

The combination of aerial images acquired in the visible and near infrared spectral ranges is particularly relevant for agricultural and environmental survey. In unmanned aerial vehicle imagery, such a combination can be achieved using a set of several embedded cameras mounted close to each other, followed by an image registration step. However, due to the different nature of source images, usual registration techniques based on feature point matching are limited when dealing with blended vegetation and bare soil patterns. Here, another approach is proposed based on image spatial frequency analysis. This approach, which relies on the Fourier-Mellin transform, has been adapted to homographic registration and distortion issues. It has been successfully tested on various aerial image sets, and has proved to be particularly robust and accurate, providing a registration error below 0.3 pixels in most cases.