Temperature and plant genotype alter alkaloid concentrations in ryegrass infected with an epichloё endophyte and this affects an insect herbivore.

Asexual Epichloё endophytes colonise agricultural forage grasses in a relationship which is mutually beneficial and provides the host plant with protection against herbivorous insects. The endophyte strain AR37 (Epichloё festucae var. lolii) produces epoxy-janthitrem alkaloids and is the only endophyte known to provide ryegrass with resistance against porina larvae (Wiseana cervinata (Walker)), a major pasture pest in cooler areas of New Zealand. This study examined the effect of temperature on concentrations of epoxy-janthitrems in AR37-infected ryegrass and determined how the resulting variations in concentration affected consumption, growth and survival of porina larvae. Twenty replicate pairs of perennial (Lolium perenne L.) and Italian ryegrass (Lolium multiflorum Lam.) plants with and without endophyte were prepared by cloning, with one of each pair grown at either high (20°C) or low (7°C) temperature. After 10 weeks, herbage on each plant was harvested, divided into leaf and pseudostem, then freeze dried and ground. Leaf and pseudostem material was then incorporated separately into semi-synthetic diets which were fed to porina larvae in a bioassay over 3 weeks. Epoxy-janthitrem concentrations within the plant materials and the semi-synthetic diets were analysed by HPLC. AR37-infected ryegrass grown at high temperature contained high in planta concentrations of epoxy-janthitrem (30.6 µg/g in leaves and 83.9 µg/g in pseudostems) that had a strong anti-feedant effect on porina larvae when incorporated into their diets, reducing their survival by 25-42% on pseudostems. In comparison, in planta epoxy-janthitrem concentrations in AR37-infected ryegrass grown at low temperature were very low (0.67 µg/g in leaves and 7.4 µg/g in pseudostems) resulting in a small anti-feedant effect in perennial but not in Italian ryegrass. Although alkaloid concentrations were greatly reduced by low temperature this reduction did not occur until after 4 weeks of exposure. Alkaloid concentrations were slightly lower in Italian than in perennial ryegrass and concentrations were higher in the pseudostems when compared with the leaves. In conclusion, epoxy-janthitrems expressed by the AR37 endophyte show strong activity against porina larvae. However, when ryegrass plants are grown at a constant low temperature for an extended period of time in planta epoxy-janthitrem concentrations are greatly reduced and are les

Dynamic risk management

This article develops a dynamic risk management model to determine a firm's optimal risk management strategy. This strategy has two elements. First, for low-leverage values, the firm fully hedges its operating cash flow exposure, due to the convexity of its cost of capital. When leverage exceeds a very high threshold, the firm gambles for resurrection and stops hedging. Second, the firm manages its capital structure through dividend distributions and investment. When leverage is low, the firm replaces depreciated assets, fully invests in opportunities if they arise, and distribute dividends, all of these together to achieve its optimal capital structure. As leverage increases, the firm stops paying dividends, while fully investing. After a certain leverage, the firm also reduces investment until it stops investing completely. The model predictions are consistent with empirical observation

Screening Protocols for Group B Streptococcus: Are Transport Media Appropriate?

Objective: To evaluate group B streptococcus (GBS) detection in an in vitro setting, using a low and controlled inoculum from swabs directly inoculated into a selective medium, as compared to delayed inoculation following a period in a commercial Amies transport medium with charcoal (Venturi Transystem(™) Copan, Italy). Study design: Clinical isolates of GBS (n = 103), were inoculated into the Amies transport medium with charcoal in a concentration of 100 colony-forming units (cfu)/ml (10 cfu/swab). Swabs were then transferred to an enrichment broth (NPC) at time intervals of 0, 2, 4, 6 and 24 hours. Broths were then incubated for 18–24 hours at 35(°)C in air, before being transferred to New Granada Medium Modified (NGM) for GBS detection and incubated for a further 18–24 hours at 35(°)C in air. If the characteristic orange pigmented colonies were observed after this period, the specimen was recorded as + (1–10 colonies) or ++ (more than 10 colonies). Results: Overall 92.2% (95/103) of isolates were detected in all tubes and at all times. An additional two isolates were non-hemolytic, non-pigment forming GBS. Of note, 3.9% (4/103) were negative until 2 hours delayed inoculation and 1.9% (2/103) gave inconsistent results, likely due to the low inoculum used. Conclusion: Delayed inoculation into selective enrichment broth following a period in transport medium, even with a low inoculum, gave a similar and acceptable GBS detection rate to direct inoculation. Hence, Amies transport medium with charcoal is an appropriate transport medium to use, where it is not practical for clinical specimens to be directly inoculated into selective enrichment broth and as endorsed in the Centers for Diseases Control (CDC) Guidelines, 2002