Volatiles from Merino fleece evoke antennal and behavioural responses in the Australian sheep blow fly Lucilia cuprina.

To identify flystrike-related volatile compounds in wool from Merino sheep, the attractiveness of wool to Lucilia cuprina Wiedmann (Diptera: Calliphoridae) was examined. First, a selection of wool samples guided by previous knowledge of sheep lines, predicted to be more susceptible or more resistant to flystrike, was tested. The attractiveness of the 10 samples selected was not associated with field susceptibility: two samples from the more resistant line were identified as most attractive and two samples from the more susceptible line were identified as least attractive, based on the behavioural assays with gravid flies. Comparison of the headspace volatiles of these samples, using solid phase microextraction and gas chromatography-mass spectrometry-electroantennographic detection, revealed octanal and nonanal to be present in the attractive wool samples that elicited responses from the fly antenna. Furthermore, the two compounds were not present in wool that was least attractive to L. cuprina. In laboratory bioassays, octanal and nonanal evoked antennal and behavioural responses in gravid L. cuprina, thus confirming their potential role as semiochemicals responsible for attracting L. cuprina to Merino sheep.

Procyanidin A2 in the Australian plant Alectryon oleifolius has anthelmintic activity against equine cyathostomins in vitro.

There is a need to investigate new methods of controlling cyathostomins in horses due to increasing anthelmintic resistance amongst these parasites. In a previous study we identified the Australian plant Alectryon oleifolius as having anthelmintic activity towards cyathostomins. This study aimed to isolate and identify the bioactive compound(s) responsible for all or part of this anthelmintic activity and quantify its activity in vitro. The condensed tannin procyanidin A2 was isolated from the plant through a process of bioassay guided fractionation and identified using 1D and 2D nuclear magnetic resonance spectroscopy and high performance liquid chromatography with mass spectrometry. Procyanidin A2 demonstrated significant anthelmintic activity in larval development assays, completely inhibiting development from egg to third larval stage at concentrations as low as 50µg/mL and having an IC50 value of 12.6µg/mL. Procyanidin A2 also significantly inhibited larval migration at concentrations of 25µg/mL. This study indicates that procyanidin A2 is the principal anthelmintic compound in extracts from A. oleifolius, and further highlights the potential for the use of this plant as a component of cyathostomin control programs in the future.

Establishing alighting preferences and species transmission differences for Pea seed-borne mosaic virus aphid vectors.

Pea seed-borne mosaic virus (PSbMV) infection causes a serious disease of field pea (Pisum sativum) crops worldwide. The PSbMV transmission efficiencies of five aphid species previously found landing in south-west Australian pea crops in which PSbMV was spreading were studied. With plants of susceptible pea cv. Kaspa, the transmission efficiencies of Aphis craccivora, Myzus persicae, Acyrthosiphon kondoi and Rhopalosiphum padi were 27%, 26%, 6% and 3%, respectively. Lipaphis erysimi did not transmit PSbMV in these experiments. The transmission efficiencies found for M. persicae and A. craccivora resembled earlier findings, but PSbMV vector transmission efficiency data were unavailable for A. kondoi, R. padi and L. erysimi. With plants of partially PSbMV resistant pea cv. PBA Twilight, transmission efficiencies of M. persicae, A. craccivora and R. padi were 16%, 12% and 1%, respectively, reflecting putative partial resistance to aphid inoculation. To examine aphid alighting preferences over time, free-choice assays were conducted with two aphid species representing efficient (M. persicae) and inefficient (R. padi) vector species. For this, alatae were set free on multiple occasions (10-15 repetitions each) amongst PSbMV-infected and mock-inoculated pea or faba bean (Vicia faba) plants. Following release, non-viruliferous R. padi alatae exhibited a general preference for PSbMV-infected pea and faba bean plants after 30min-4h, but preferred mock-inoculated plants after 24h. In contrast, non-viruliferous M. persicae alatae alighted on mock-inoculated pea plants preferentially for up to 48h following their release. With faba bean, M. persicae preferred infected plants at the front of assay cages, but mock-inoculated ones their backs, apparently due to increased levels of natural light there. When preliminary analyses were performed to detect PSbMV-induced changes in the volatile organic compound profiles of pea and faba bean plants, higher numbers of volatiles representing a range of compound groups (such as aldehydes, ketones and esters) were found in the headspaces of PSbMV-infected than of mock-inoculated pea or faba bean plants. This indicates PSbMV induces physiological changes in these hosts which manifest as altered volatile emissions. These alterations could be responsible for the differences in alighting preferences. Information from this study enhances understanding of virus-vector relationships in the PSbMV-pea and faba bean pathosystems.

Parental environment changes the dormancy state and karrikinolide response of Brassica tournefortii seeds.

BACKGROUND AND AIMS: The smoke-derived chemical karrikinolide (KAR(1)) shows potential as a tool to synchronize the germination of seeds for weed management and restoration. To assess its feasibility we need to understand why seeds from different populations of a species exhibit distinct responses to KAR(1). Environmental conditions during seed development, known as the parental environment, influence seed dormancy so we predicted that parental environment would also drive the KAR(1)-responses of seeds. Specifically, we hypothesized that (a) a common environment will unify the KAR(1)-responses of different populations, (b) a single population grown under different environmental conditions will exhibit different KAR(1)-responses, and (c) drought stress, as a particular feature of the parental environment, will make seeds less dormant and more responsive to KAR(1). METHODS: Seeds of the weed Brassica tournefortii were collected from four locations in Western Australia and were sown in common gardens at two field sites, to test whether their KAR(1)-responses could be unified by a common environment. To test the effects of drought on KAR(1)-response, plants were grown in a glasshouse and subjected to water stress. For each trial, the germination responses of the next generation of seeds were assessed. KEY RESULTS: The KAR(1)-responses of seeds differed among populations, but this variation was reduced when seeds developed in a common environment. The KAR(1)-responses of each population changed when seeds developed in different environments. Different parental environments affected germination responses of the populations differently, showing that parental environment interacts with genetics to determine KAR(1)-responses. Seeds from droughted plants were 5 % more responsive to KAR(1) and 5 % less dormant than seeds from well-watered plants, but KAR(1)-responses and dormancy state were not intrinsically linked in all experiments. CONCLUSIONS: The parental environment in which seeds develop is one of the key drivers of the KAR(1)-responses of seeds.