Histology of witches' brooms on Betula pubescens

Witches' brooms caused by Taphrina betulina on Betula pubescens formed from the development of large numbers of axillary shoots on infected buds. Broom shoots showed vigorous growth during the first season, but died in the second or third year after initiation. Occasional adventitious root production was noted at the base of broom shoots. Cortex and secondary phloem tissues of the central gall-like structure of the brooms expanded. The bark of infected material lacked brachysclereids, and tangential ray parenchyma of the secondary phloem were also absent. Numerous shoot bases and aborted axillary buds were present within the bark. Abundant starch granules were present, especially in the phellogen and phelloderm layers. Distortion of the internal lignified tissues was due to the presence of multiple vascular connections from the proliferation of shoots on the broom.     

Organogenesis and embryogenesis in mature zygotic embryos of Picea sitchensis

Differentiation of adventitious buds and somatic embryos from mature zygotic embryos of Picea sitchensis (Bong.) Carr. is described. Adventitious buds were formed on embryos pulse-treated with 250 microM benzyladenine for 2 h and cultured on medium lacking growth regulators. Buds were initiated at different frequencies and sites depending on when the BA-pulsed embryos were transferred to fresh culture medium. Embryogenic callus was formed when the zygotic embryos were cultured on medium containing 10 microM 2,4-dichlorophenoxyacetic acid and 5 microM benzyladenine. Although 50% of the embryos gave rise to embryogenic callus, only 20% of the callus continued to proliferate after subculture. Proliferation of new somatic embryos occurred from both the embryonic region and the suspensor region on previously formed somatic embryos. The pattern for development of adventitious buds and somatic embryos in Picea sitchensis is compared to that in Picea abies under similar culture conditions.     

Specific hybridization real‐time PCR probes for Phytophthora ramorum detection and diagnosis

Sudden Oak Death, caused by Phytophthora ramorum, poses a serious threat to native American oaks, and is also present in Europe where it has been isolated from numerous European ornamental plant nurseries. Its proven aggressiveness against plants in the Fagaceae and Ericaceae and the damage it has caused in North America have lead to it being assigned quarantine status. The timely and accurate detection of P. ramorum is a critical aid in the study of the epidemiology and biology of this pathogen. As a regulated organism, the availability of a sensitive and reliable assay is essential when attempting to achieve early detection of the pathogen. In this work, new specific hybridization probes for a real‐time PCR amplification method were found to be rapid, robust and labour‐saving, and proved suitable for routine use in a molecular diagnostic laboratory.     

In vitro sensitivity of the amphibian pathogen Batrachochytrium dendrobatidis to antifungal therapeutics

Chytridiomycosis, a skin disease caused by Batrachochytrium dendrobatidis, has caused amphibian declines worldwide. Amphibians can be treated by percutaneous application of antimicrobials, but knowledge of in vitro susceptibility is lacking. Using a modified broth microdilution method, we describe the in vitro sensitivity of two Australian isolates of B. dendrobatidis to six antimicrobial agents. Growth inhibition was observed, by measurement of optical density, with all agents. Minimum inhibitory concentrations (µg/ml; isolate 1/2) were – voriconazole 0.016/0.008; itraconazole 0.032/0.016; terbinafine 0.063/0.063; fluconazole 0.31/0.31; chloramphenicol 12.5/12.5; amphotericin B 12.5/6.25. Killing effects on zoospores were assessed by observing motility. Amphotericin B and terbinafine killed zoospores within 5 and 30 min depending on concentration, but other antimicrobials were not effective at the highest concentrations tested (100 µg/ml). This knowledge will help in drug selection and treatment optimization. As terbinafine was potent and has rapid effects, study of its pharmacokinetics, safety and efficacy is recommended.     

The regulation of fish medicines - UK and European Union aspects

There is a significant body of legislation affecting veterinary medicines, including those intended for use in fish. However, the main criteria for authorization remain quality, efficacy and safety. Safety for humans, both operators and consumers, is of paramount importance in the assessment process. Consumer safety is largely addressed through the maximum residue limit (MRL) approach with withdrawal periods being established to ensure that the MRL is not exceeded? Residues monitoring plays an important role in ensuring that withdrawal periods are observed and that illegal drugs are not used.     

Resilience of microorganisms and aggregation of a sandy calcareous soil to amendment with organic and synthetic fertilizer

Marginal coastal soils are dependent on appropriate land management to prevent soil erosion, as a result of low soil stability combined with exposure to strong winds. An example of such an area is the machair, a fixed dune system utilized for agriculture in the northwest of Scotland, UK. The separate and combined effects of synthetic NPK fertilizer and a traditional soil conditioner (kelp, a seaweed) on soil structure formation, stabilization and biological parameters were studied on a cropped field on the machair. Soil physical properties examined included water retention at 10 kPa matric suction, water stable aggregates (WSA) >1 mm, aggregate stability, and biological properties including ester-linked fatty acid (ELFA) analysis and β-glucosidase activity for microbial biomass and activity, respectively. Significant treatment effects were few and inconsistent between sampling times, but included kelp and/or NPK fertilizer reducing aggregation, water retention, microbial biomass and activity relative to the unamended control treatment. Furthermore, seasonal variation, which could be attributed to changes in soil water content, was stronger than variation in response to fertilizer treatments. Principal components analysis of the ELFA data showed that ploughing promoted fungal biomass relative to bacteria, and confirmed both the absence of consistent synthetic and organic fertilizer effects and the sensitivity of microbial biomass to season. Overall, the study demonstrated the resilience of a calcareous sandy soil to amendment with fertilizer.