Mapping of QTL for seed dormancy in a winter oilseed rape doubled haploid population

Following winter oilseed rape cultivation, considerable numbers of volunteer oilseed rape plants may occur in subsequent years in following crops. The appearance of volunteer oilseed rape plants is based on the capability of the seeds to become secondary dormant and to survive in this stage for many years in the soil. Genetic reduction of secondary seed dormancy in oilseed rape could provide a means to reduce the frequency of volunteer plants and especially the dispersal of transgenic oilseed rape. The objective of the present study was to analyse the inheritance of primary and secondary seed dormancy in a winter oilseed rape doubled haploid population derived from the cross Express 617 × R53 and to study correlations to other seed traits. Field experiments were performed in Germany for 2 years at two locations with two replicates. Seeds harvested from open pollinated plants were used for all analyses, including a laboratory test for seed dormancy. A previously developed molecular marker map of the doubled haploid population was used to map QTL of the relevant traits. For primary, secondary and total seed dormancy, the results showed significant effects of the genotypes and their interactions, with years and locations. Two, four and five QTL were detected for primary, secondary and total seed dormancy which explained 19, 35 and 42 % of the phenotypic variance, respectively. Results show that secondary seed dormancy is a heritable trait and that selection for low secondary seed dormancy is possible.     

Habitat selection by adult Golden Eagles Aquila chrysaetos during the breeding season and implications for wind farm establishment

Capsule: Global Positioning System (GPS)-tagged adult Golden Eagles Aquila chrysaetos breeding in forests in northern Sweden selected clear-cuts, coniferous forests with lichens and steep slopes during the breeding season but avoided wetlands and mixed forest.

Aims: To investigate the habitat selection patterns of tree-nesting Golden Eagles, and identify how potential conflicts with wind farm development could be minimized.

Methods: The study is based on GPS tracking data from 22 adult eagles. We estimated home range sizes using a biased random bridge approach and habitat selection patterns using resource selection functions following a use-availability design.

Results: Core home range size among adults was variable during the breeding season (5–30?km²). Individual movement extents were variable, but sexes did not significantly differ in their scale of movement. At the landscape scale, individuals selected for clear-cuts and coniferous forest with ground lichens, whereas wetland, water bodies and mixed forest were avoided. Steeper and south facing slopes were selected for, whereas, north facing slopes were avoided.

Conclusions: Potential conflicts between eagles and wind energy establishment can be reduced if wind farms are placed away from steep slopes, minimizing areas that are clear-cut during construction, and locating turbines within dense, young and other less favoured forest habitats.     

Liquid culture mass production of biocontrol nematodes,<Emphasis Type="Italic"> Heterorhabditis bacteriophora</Emphasis> (Nematoda: Rhabditida): improved timing of dauer juvenile inoculation

Heterorhabditis bacteriophora is used in biological control of soil-borne insect pests in horticulture and turf. Mass production is carried out in monoxenic liquid cultures pre-incubated with the symbiont of the nematodes, the bacterium Photorhabdus luminescens, before nematode dauer juveniles (DJ) are inoculated. As a response to bacterial food signals, the DJ recover from the developmentally arrested dauer stage, grow to adults and produce DJ offspring. Variable DJ recovery after inoculation into cultures of P. luminescens often causes process failure due to low numbers of adult nematodes in the medium. In order to enhance DJ recovery, improve nematode population management and increase yields, the optimal timing for DJ inoculation was sought. The process parameter pH and respiration quotient (RQ) were recorded in order to test whether changes can be used to identify the best moment for DJ inoculation. When DJ were inoculated during the lag and early logarithmic growth phases of P. luminescens cultures, DJ recovery was low and almost no nematode reproduction was obtained. High populations of P. luminescens phase variants were recorded. Recovery and yields increased when DJ were inoculated during the latter log phase during which the RQ dropped to values <0.8 and the pH reached a maximum. The highest DJ recovery and yields were observed in cultures that were inoculated during the late stationary growth phase. This period started with the increase of the pH after its distinct minimum at pH <8.0. Thus optimal timing for DJ inoculation can be defined through monitoring of the pH in the P. luminescens culture.     

Reversible Membrane Pearling in Live Cells upon Destruction of the Actin Cortex

Membrane pearling in live cells is observed when the plasma membrane is depleted of its support, the cortical actin network. Upon efficient depolymerization of actin, pearls of variable size are formed, which are connected by nanotubes of ∼40 nm diameter. We show that formation of the membrane tubes and their transition into chains of pearls do not require external tension, and that they neither depend on microtubule-based molecular motors nor pressure generated by myosin-II. Pearling thus differs from blebbing. The pearling state is stable as long as actin is prevented from polymerizing. When polymerization is restored, the pearls are retracted into the cell, indicating continuity of the membrane. Our data suggest that the alternation of pearls and strings is an energetically favored state of the unsupported plasma membrane, and that one of the functions of the actin cortex is to prevent the membrane from spontaneously assuming this configuration.     

The rise and fall of an epizootic of the diphyllobothriidean cestode Schistocephalus pungitii infecting the ninespine stickleback

Epizootics of diphyllobothriidean cestodes appear to be simple, but deceptive similarity conceals the myriad ways in which these events are shaped by complex abiotic and biotic interactions. In Dog Bone Lake, Alaska, an epizootic of Schistocephalus pungitii infecting the ninespine stickleback (Pungitius pungitius) was short-lived. Its duration, with a peak that lasted only 1 yr, was shorter than for previously documented epizootics in Schistocephalus solidus . The ability of the ninespine stickleback to sustain infections, which appears to be related to species-specific characteristics of the host, may have played an important role in shaping the epizootic. Moreover, the epizootic of S. pungitii was not coincident with those observed for S. solidus in earlier studies within this region, supporting the hypothesis that processes involved in epizootics largely reflect local (lake-level) influences on population dynamics of the parasite. The outbreak occurred at a time when the host population was not relatively dense, which is inconsistent with epidemiological theory and may be a consequence of the parasite's indirect life cycle. The variability of the unregulated and unstable epizootic events of diphyllobothriidean cestodes presents a challenge to understand the ecological and evolutionary factors influencing the prevalence of infections in host populations.     

QTL for phytosterol and sinapate ester content in <Emphasis Type="Italic">Brassica napus</Emphasis> L. collocate with the two erucic acid genes

Improving oil and protein quality for food and feed purposes is an important goal in rapeseed (Brassica napus L.) breeding programs. Rapeseed contains phytosterols, used to enrich food products, and sinapate esters, which are limiting the utilization of rapeseed proteins in the feed industry. Increasing the phytosterol content of oil and lowering sinapate ester content of meal could increase the value of the oilseed rape crop. The objective of the present study was to identify quantitative trait loci (QTL) for phytosterol and sinapate ester content in a winter rapeseed population of 148 doubled haploid lines, previously found to have a large variation for these two traits. This population also segregated for the two erucic acid genes. A close negative correlation was found between erucic acid and phytosterol content (Spearman’s rank correlation, r _s = −0.80^**). For total phytosterol content, three QTL were detected, explaining 60% of the genetic variance. The two QTL with the strongest additive effects were mapped on linkage groups N8 and N13 within the confidence intervals of the two erucic acid genes. For sinapate ester content four QTL were detected, explaining 53% of the genetic variance. Again, a close negative correlation was found between erucic acid and sinapate ester content (r _s = −0.66^**) and the QTL with the strongest additive effects mapped on linkage groups N8 and N13 within the confidence intervals of the two erucic acid genes. The results suggests, that there is a pleiotropic effect of the two erucic acid genes on phytosterol and sinapate ester content; the effect of the alleles for low erucic acid content is to increase phytosterol and sinapate ester content. Possible reasons for this are discussed based on known biosynthetic pathways. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Photochemistry of dyes and fluorochromes used in biology and medicine: some physicochemical background and current applications

An overview of the basic principles of photochemistry is presented to facilitate discussion of fluorescence, quenching and quantum yields. These topics in turn provide the foundation for an account of fluorescence spectroscopy and its application to microscopy. A brief overview of light microscopy and the application of fluorescence microscopy is given. The influences of molecular features, such as aromatic character and substitution patterns, on color and fluorescence are described. The concept of color fading is considered with particular reference to its effect on microscopic preparations. A survey of representative fluorescent probes is provided, and their sensitivity, application, and limitations are described. The phototoxicity of fluorescent molecules is discussed using biomembranes and DNA as examples of targets of toxicity. Photodynamic therapy, a relatively new clinical application of phototoxicity, is described. Both anticancer and antimicrobial applications are noted, and an assessment is given of the current ideas on the ideal physicochemical properties of the sensitizing agents for such applications.