Floodplain ecosystem response to climate variability and land-cover and land-use change in Lower Missouri River basin

This contribution aims at characterizing the extreme responses of Lower Missouri River basin ecosystems to land use modification and climate change over a 30-year temporal extent, using long term Landsat data archives spanning from 1975 to 2010. The inter-annual coefficient of variation (CoV) of normalized difference vegetation index was used as a measure of vegetation dynamics to address ecological consequences associated with climate change and the impact of land-cover/land-use change. The slope of a linear regression of inter-annual CoV over the entire time span was used as a sustainability indicator to assess the trend of vegetation dynamics from 1975 to 2010. Deduced vegetation dynamics were then associated with precipitation patterns, land surface temperature, and the impact of levees on alluvial hydrologic partitioning and river channelization reflecting the links between society and natural systems. The results show, a higher inter-annual accumulated vegetation index, and lower inter-annual CoV distributed over the uplands remaining virtually stable over the time frame investigated; relatively low vegetation index with larger CoV was observed over lowlands, indicating that climate change was not the only factor affecting ecosystem alterations in the Missouri River floodplain. We cautiously conclude that river channelization, suburbanization and agricultural activities were the possible potential driving forces behind vegetation cover alteration and habitat fragmentation on the Lower Missouri River floodplain.     

A new tool for entry and analysis of virulence data for plant pathogens

The methods of Habgood (1970) and Gilmour (1973) for the assignment of pathogen race names are discussed and the advantages of a reversed octal system, based on Gilmour's octal code, are emphasized. A new spreadsheet, 'HaGiS', exploits these two designation systems to provide user-friendly and fast access to some routine steps in the analysis of virulence data for plant pathogen populations. It produces graphs and tables for frequency distributions (of pathotypes, isolate complexities and cultivar susceptibilities); sorted lists (e.g. of the races ranked by predominance); indices (of sample diversity and of pathogenicity for each differential cultivar); and coloured proximity matrices. Use of HaGiS requires knowledge of only a few basic functions of MS Excel 97^®. All graphs, tables, indices and matrices are generated automatically and displayed by switching to the corresponding worksheet. In addition to data analysis, the spreadsheet is convenient for the entry of experimental data, allowing for all commonly used assessment scales.     

New evidence on a cold case: trophic transmission, distribution and host-specificity in Hedruris spinigera (Nematoda: Hedruridae)

The life cycle of Hedruris spinigera Baylis, 1931 (Nematoda: Hedruridae) is determined here with the first formal identification of the parasite's intermediate host: the crustacean amphipod Paracorophium excavatum Thomson. Adult H. spinigera are redescribed from specimens collected from the stomach of fishes, Retropinna retropinna (Richardson) and Aldrichettaforsteri (Valenciennes), from Lake Waihola, New Zealand. Immature adults of the parasite collected from intermediate hosts (P. excavatum) are also described for the first time. The prevalence, abundance and intensity of infection of H. spinigera in several fish species are quantified along with the occurrence of P. excavatum, the parasite's intermediate host, in fish stomach contents. Although H. spinigera's transmission mode (trophic transmission) and fish diet potentially expose all fish species to infection, some level of host specificity must exist as parasite prevalence, abundance and intensity of infection vary greatly between potential definitive host species. We suggest here that the anatomy of the fish digestive tract and especially that of the stomach plays an important role in host suitability for H. spinigera. While P. excavatum is the only intermediate host in Lake Waihola, H. spinigera was found in six different fish species: Aldrichetta forsteri, Galaxias maculatus (Jenyns), Retropinna retropinna, Rhombosolea retiaria Hutton, Perca fluviatilis Linnaeus and Salmo trutta Linnaeus; although typical hedrurid attachment and mating positions were observed only in R. retropinna and A. forsteri. The limited distribution of H. spinigera is most likely due to that of its different host species (intermediate and definitive), all inhabitants of coastal fresh and brackish waters.     

A DNA Probe for Rapid Screening of Sugar Beet (Beta vulgaris L.) Carrying Extra Chromosomes from Wild Beets of the Procumbentes Section

Genes from wild species of the Procumbentes section can be transferred to sugar beet chromosomes via translocations. Since large translocations, including for example a gene for nematode resistance, generally result in meiotic disturbances, there is a need to select new diploid resistant beets from progenies of monosomic wild beet addition lines. A dispersed repetitive DNA probe, which is closely correlated with the resistance gene and hybridizes exclusively with wild beet DNA, appears to be highly superior to selection based on isozyme markers. Characteristic ‘fingerprints’ on the available monosomic addition lines reveal the existence of at last 5 different chromosomes in the wild species each housing a gene for nematode resistance. This probe can be used advantageously to identify individuals carrying the intact or fragmented wild beet chromosomes, or even various amounts of translocated chromatin. Strategies are discussed for the identification of new translocation types using straightforward squash dot or Southern hybridization techniques in combination with the wild beet DNA probe.     

Human guanylate-binding protein 1 as a model system investigated by several surface techniques

In medical technologies concerning the surface immobilization of proteins in a defined orientation, maintaining their activity is a critical aspect. Therefore, in this study, the authors have investigated the activity of an elongated protein attached to a self-assembled monolayer supported streptavidin layer for different relative orientations of the protein with regard to the surface. Several mutants of this protein, human guanylate-binding protein 1 (hGBP1) showing GTPase catalytic activity, have been furnished with either one or two biotin anchors. Various independent methods that are based on different biophysical properties such as surface plasmon resonance, atomic force microscopy, and quartz crystal microbalance have been used to determine the orientation of the hGBP1 variants after anchoring them via a streptavidin-linker to a biotinylated surface. The activity of guanosine-triphosphate hydrolysis of hGBP1 monomers bound on the surface is found to depend on their orientation relative to the substrate, relating to their ability to form dimers with other neighboring anchored mutants; the maximum activity is lower than that observed in solutions, as might be expected from diffusion limitations at the solid/liquid interface on the one hand and prevention from homodimer formation due to immobilization on the other hand.     

Sample size for diversity studies in tetraploid alfalfa (<Emphasis Type="Italic">Medicago sativa</Emphasis>) based on codominantly coded SSR markers

The number of genotypes investigated per population is important for the reliability of diversity studies. The objective of this study was to determine the sample size for the identification of differences among populations of an outcrossing autotetraploid species, alfalfa (Medicago sativa), using codominantly coded SSR markers. One hundred and twenty genotypes from each of two closely related populations were analysed with two markers. Twenty random subsamples for each of three sample sizes (10, 20 and 40 genotypes) were built. Compared to the populations with 120 genotypes, alleles that were no longer present in subsamples with 40 genotypes were mainly rare, whereas abundant alleles were also excluded in subsamples with 10 genotypes. F _ST values for pairs of subsamples between the two populations were always significantly different based on 40 genotypes, whereas for 10 genotypes more than half of the pairs were not significantly different. We concluded that 40 genotypes are a reasonable sample size for diversity studies with closely related populations of tetraploid alfalfa investigated with SSR markers. Twenty genotypes may be an economical alternative for large scale studies, but 10 genotypes were a too low number for reliable results.     

Ground-level hyperspectral imagery for detecting weeds in wheat fields

Site-specific weed management can allow more efficient weed control from both an environmental and an economic perspective. Spectral differences between plant species may lead to the ability to separate wheat from weeds. The study used ground-level image spectroscopy data, with high spectral and spatial resolutions, for detecting annual grasses and broadleaf weeds in wheat fields. The image pixels were used to cross-validate partial least squares discriminant analysis classification models. The best model was chosen by comparing the cross-validation confusion matrices in terms of their variances and Cohen’s Kappa values. This best model used four classes: broadleaf, grass weeds, soil and wheat and resulted in Kappa of 0.79 and total accuracy of 85 %. Each of the classes contains both sunlit and shaded data. The variable importance in projection method was applied in order to locate the most important spectral regions for each of the classes. It was found that the red-edge is the most important region for the vegetation classes. Ground truth pixels were randomly selected and their confusion matrix resulted in a Kappa of 0.63 and total accuracy of 72 %. The results obtained were reasonable although the model used wheat and weeds from different growth stages, acquisition dates and fields. It was concluded that high spectral and spatial resolutions can provide separation between wheat and weeds based on their spectral data. The results show feasibility for up-scaling the spectral methods to air or spaceborne sensors as well as developing ground-level application.