12903 research outputs found
Sort by
How to chew gum: the post-ingestion fate of foliar secondary compounds consumed by a eucalypt herbivore
Get PDFHerbivorous insects require mechanisms to deal with defence compounds produced by their host plants. Despite an array of secondary compounds associated with defence, eucalypts are hosts to many insect species that readily obtain nutrients also produced by these plants. Gonipterus weevils are foliage-feeding eucalypt specialists as larvae and adults, with a notable characteristic of protecting their eggs with a hardened frass-like substance. The aim of this study was to assess plant, weevil frass and egg capsule chemistry to determine how the weevil eliminates plant secondary metabolites. We hypothesised that noxious compounds would be metabolised prior to elimination and that egg capsules would be composed of frass and additional substances. Weevils were fed on Eucalyptus globulus plants for seven days, with their frass and egg capsules collected daily, and the damaged, first, fully-expanded leaves of the host collected at the end of the assay. Compounds present in each sample were extracted in hexane and analysed by gas chromatography-mass spectrometry. The most abundant compounds in each sample were waxes and terpenoids, and metabolism of 1,8-cineole was evident, with two metabolites that may have semiochemical activity. Comparative analysis revealed significant differences between all samples, with shared compounds varying in relative proportions and exclusive compounds in sample type. These findings contribute to the understanding of Gonipterus physiology and highlight the differences between frass and the cover of egg capsules
Optimization and application of bacterial environmental DNA and RNA isolation for qualitative and quantitative studies
Get PDFMolecular detection of environmental DNA (eDNA) and RNA (eRNA) allows highly sensitive qualitative (i.e., presence or absence) and quantitative (i.e., abundance) monitoring of aquatic bacteria. However, bacterial molecular diagnostics are limited by low positive predictive values. Protocols for bacterial eDNA and eRNA molecular monitoring have primarily focused on optimizing specimen collection, and the optimal method to purify bacterial nucleic material from postcollection aquatic specimens to maximize the analytical sensitivity of molecular diagnostics remains poorly defined. Accordingly, strategies to isolate bacterial eDNA and eRNA from fresh and saltwater were investigated. We evaluated two filtration and four nucleic acid purification systems as representative of current generation bacterial eDNA and eRNA isolation strategies for capacity to isolate bacterial eDNA and eRNA from prelysed (i.e., free-nucleic acids) and viable (i.e., colony forming units, CFU) bacterial cells. We also compared the sensitivities of reverse transcription quantitative PCR (RT-qPCR) and metagenomic shotgun microbiome sequencing. The optimal protocol used 0.7 μm borosilicate glass filters (Whatman plc) followed by extraction with the RNeasy PowerWater kit (Qiagen). The protocol had a very high analytical sensitivity (10−3–100 ng and 102–101 CFU detected in 500 mL) across multiple species of bacteria, when tested with either RTqPCR or metagenomic sequencing. Importantly, this study highlighted several limitations which are restrictive to both qualitative and quantitative bacterial eDNA and eRNA studies. First, a 12-h time course between sampling and extraction revealed significant species-specific changes in cell number and free-nucleic acid concentrations can occur postspecimen collection. Second, we found Gram-positive bacteria yielded less nucleic material compared to Gram-negative bacteria suggesting bacterial eDNA and eRNA studies could be biased by microorganism genome stability and extraction efficiency. This study highlights the need to define the species-specific diagnostic sensitivity of a protocol when monitoring aquatic bacterial eDNA and eRNA with molecular diagnostics
Comprehensive analysis of glulam delamination through finite element modelling considering heat and mass transfer, plasticity and fracture mechanics: a case study using high density hardwood
Get PDFWith the ongoing emphasis on sustainable and eco-friendly construction, there is a rising demand for high-strength and high-stiffness engineered wood products. This trend presents both opportunities and challenges for the Australia’s hardwood industry, particularly concerning native forest-grown spotted gum (Corymbia citriodora). Glue laminated (glulam) spotted gum beams cannot be confidently commercialised due to the difficulty for its high-density to satisfy the bond integrity criteria (referred to as “delamination test”) for external products in accordance with the Australia and New Zealand Standard AS/NZS 1328.1. For in-depth understanding of the delamination process, an accurate numerical model represents a valuable and time-efficient tool. The aim of this study is to develop and detail such a model, considering heat and mass transfer, drying stresses, plasticity and fracture propagation models, using COMSOL Multiphysics 5.5. The model was validated against a series of wetting and drying experiments on spotted gum glulam, considering both moisture content variation and crack propagation along the gluelines. Results from the validated model showed that delamination is principally due to the tensile stress applied to the gluelines
Half a century of citizen science tag-recapture data reveals stock delineation and cross-jurisdictional connectivity of an iconic pelagic fish
Get PDFTag-recapture programs to monitor the movements of fish populations are among some of the longest-running citizen-science datasets to date. Here, using half a century of yellowtail kingfish (Seriola lalandi, Carangidae) tag-recapture data collected through citizen-science projects, we report novel insights into population connectivity in Australia and New Zealand (NZ). Despite the importance of kingfish in commercial and recreational fisheries, substantial knowledge gaps about their stock structure and connectivity between jurisdictions hinder current management efforts. Between 1974 and 2022, 63,432 releases and 4636 recaptures (7.3%) of tagged kingfish were collected in Australia and NZ. Most tagged individuals (51.4%) were recaptured within 10 km of their original release location up to 14 years post-release (mean: 225 days), indicating some degree of site fidelity. However, 656 (14.2%) kingfish were recaptured over 100 km from their release location, with one fish travelling at least 2834 km in 702 days. Seasonal variability was evident for releases and recaptures, with more releases occurring in summer and autumn in most jurisdictions. Network analysis of recaptures revealed no connectivity between tagged kingfish from western and eastern Australia, supporting genetic delineation. By contrast, extensive connectivity exists across eastern Australia and NZ, with 87 kingfish moving between five Australian state jurisdictions, 316 individuals travelling across 15 bioregions and six kingfish moving between Australia and NZ. Our findings provide important new insights into the structure and connectivity of the eastern Australia kingfish stock and suggest increased collaboration between state and international fisheries jurisdictions may support improved stock assessment and management
Population structure of Ballot's saucer scallop (Ylistrum balloti) for the east coast of Queensland
Get PDFBallot's saucer scallops (Ylistrum balloti) are harvested by the east coast otter trawl fishery and contribute a higher proportion of the overall yearly catch than the co-located mud scallop (Amusium pleuronectes). Recent estimates of Ballot's saucer scallop biomass are below the defined limit reference point (20%), and the fishery is currently closed across much of its area (limited fishing is allowed in the southern offshore management region). An underlying assumption for fishery management is that Ballot's saucer scallops along Queensland’s east coast are one population to be managed and assessed as a single biological stock. Significant aggregations of Ballot's saucer scallops have been detected in the central trawl management region despite the low biomass estimates. Trawl fishery representatives have concerns about the single stock approach. Their observations of morphometric and colour differences between Ballot's saucer scallops from the central trawl management region and the management regions to the south are suggestive of distinct populations. To determine the population structure Fisheries Queensland used High Throughput Sequencing to identify 3217-5754 Single Nucleotide Polymorphisms (SNPs). The results indicated small (FSTs ~ 0.005), but significant (p<0.001) differences between scallops either side of 22 degrees South and was further supported by PCA, AMOVA and Admixture analyses. The study shows the existence of two populations of Ballot's saucer scallops on the east coast of Queensland
Maize Downy Mildew (Peronosclerospora neglecta) in Cambodia, Lao PDR, and Thailand
Get PDFPeronosclerospora species cause downy mildew diseases on maize (Zea mays) worldwide. Maize leaves with symptoms of downy mildew were collected from field crops in Cambodia, Lao PDR, and Thailand, during surveys between 2018 and 2022. Initial determination of the presence of downy mildew on specimens was determined microscopically by the presence of conidiophores and/or oospores in leaf tissue. Phylogenetic analyses of the cytochrome c oxidase subunit II (cox2) gene sequences showed that all specimens were Peronosclerospora neglecta. Reference specimens from Thailand were deposited at the Thai Plant Pathology Herbarium, Bangkok, Thailand, while those from Cambodia and Lao PDR were deposited at the Queensland Plant Pathology Herbarium, Australia. Peronosclerospora neglecta was widespread in field crops of maize in Cambodia, Lao PDR, and Thailand during the survey period. This is the first time that P. neglecta has been reported in Cambodia and Lao PDR. © 2024, Chiang Mai University. All rights reserved
High concentrations of piperonyl butoxide (PBO) enhance toxicity of S-methoprene against the lesser grain borer, Rhyzopertha dominica
No full textInsect growth regulators (IGRs) have been playing a major role in the effective management of a range of stored product insect pests including species that have developed resistance to major groups of insecticides, such as organophosphates (OPs) and synthetic pyrethroids (SPs). In the present study, we evaluated the efficacy of S-methoprene alone and in combination with piperonyl butoxide (PBO), an adjuvant component of insecticides for synergy, against two strains, Lab-S (susceptible) and Met-R (Methoprene resistant) of an economically important pest species, the lesser grain borer, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae). Adults of both Lab-S and Met-R strains were exposed to wheat treated with multiple concentrations of S-methoprene ranging from 0.001 to 0.01 and 10 to 60 mg/kg, respectively, alone and in combination with PBO. A variety of concentrations, including 0.27, 0.53, 0.80, and 1.07 g/kg, were evaluated for PBO. Mortality of adults and percent reduction in progeny were assessed after 14 and 65 days of treatment, respectively. As anticipated, the adult mortality rates of both strains were not significantly affected by S-methoprene alone. However, the number of progeny produced confirmed that the Met-R strain exhibited a high level of resistance to S-methoprene alone, with over 50 F1 progeny adults surviving in wheat treated with the maximal rate, 10 mg/kg. In contrast, the toxicity of S-methoprene was increased against the same resistant strain (Met-R), by 0.80 or 1.07 g/kg of PBO in combination treatment, resulting in a significant reduction in progeny numbers (25 adults per container). Although the tested concentrations of S-methoprene and PBO were well above the currently registered rate globally, our results highlight the fact that PBO enhances the toxicity of S-methoprene to some extent, reaffirming that the mode of action of the latter involves the inhibition of mixed-function oxidases (MFOs) and highlights the need for further research into developing potential binary or triplet formulations containing these two active ingredients (AIs)
Improving grain grower business resilience before, during and post drought – ARM Online tools to assist on-farm decision making
Get PDFThe Agricultural Risk Management (ARM) Online platform (www.armonline.com.au) provides growers and agronomists with digital tools that evaluate the drought resilience of alternative cropping strategies. The platform assists in choosing cropping systems that have both a high level of drought resilience and perform well across further target indicators, such as profitability. Recently, new functionality has been added to the CropARM decision-support tool that focuses on optimising tactical crop management decisions. Furthermore, the new RotationARM tool has been developed to assist in selecting resilient cropping systems. Over the coming months, a series of capacity-building workshops are being delivered to guide growers and their advisors in using these tools to build their drought resilience. Participants will learn to analyse their cropping systems and develop and refine their own rules of thumb
Who bit the boat? New DNA collection and genomic methods enable species identification in suspected shark-related incidents
No full textSpecies identification following shark-related incidents is critical for effective incident management and for collecting data to inform shark bite mitigation strategies. Witness statements are not always reliable, and identification is often ambiguous or missing. Alternative methods for species identification include morphological assessments of bite marks, analysis of collected teeth at the scene of the incident, and genetic approaches. However, access to appropriate collection media and robust genetic assays have limited the use of genetic technologies. Here, we present a case study that facilitated a unique opportunity for an experimental design to compare the effectiveness of medical gauze readily available in first-aid kits, and forensic-grade swabs in collecting genetic material for shark-species identification. Sterile medical gauze and forensic-grade swabs were used to collect transfer DNA from the bite margins on a bitten surf ski which were compared to a piece of shark tissue found embedded along the bite margin. Witness accounts and the characteristics of the bite mark impressions inferred the involvement of a Carcharodon carcharias (white shark). The morphology of a tooth found in the surf ski, however, suggested it belonged to an Orectolobus spp. (wobbegong). Genetic analysis of DNA transferred from the shark to the surf ski included the application of a broad-target nested PCR assay followed by Sanger sequencing, with white shark contribution to the ‘total sample DNA’ determined with a species-specific qPCR assay. The results of the genetic analyses were congruent between sampling methods with respect to species identification and the level of activity inferred by the donor-specific DNA contribution. These data also supported the inferences drawn from the bite mark morphology. DNA from the recovered tooth was PCR amplified with a wobbegong-specific primer pair designed for this study to corroborate the tooth’s morphological identification. Following the confirmation of gauze used for sampling in the case study event, two additional isolated incidents occurred and were sampled in situ using gauze, as typically found in a first-aid kit, by external personnel. DNA extracted from these gauze samples resulted in the identification of a white shark as the donor of the DNA collected from the bite marks in both instances. This study, involving three incidents separated by time and location, represents the seminal application of gauze as a sampling media after critical human-shark interactions and strongly supports the practical implementation of these methods in the field
Use of mill by-products in the fallow in sugarcane production in Australia
No full textMill by-products such as mud, ash and mud/ash mixtures are known to increase cane and sugar yields. Tra-ditionally, Australian growers broadcast these by-products in the fallow at rates greater than 150 t/ha. However, growers are now banding by-products at less than 100 t/ha, with few guidelines on how to maximise their returns from this prac-tice. Eight commercial size replicated, randomised strip trials were established in bare fallows between Ingham and Proserpine to investigate the impact of by-products banded between 35 and 100 t/ha and broadcast between 140 and 200 t/ha on cane yield, CCS and grower net revenue compared to standard grower fallow practices. The trials were harvested each year over the crop cycle using a commercial harvester. Tonnes of cane harvested and mill CCS provided by the receiving sugar mill were used to calculate tonnes of cane per hectare and grower net revenue per hectare using the Australian cane payment method for each plot in a trial. The application of mud, mud/ash and ash increased cane yield with ash ≥ mud/ash >> mud. The greater the quantity of by-product applied, the greater the cane yield. Conversely, CCS decreased linearly with the quantity of mud, mud/ash, or ash applied. CCS was lowest in mud mud/ash >> mud and was greatest at application rates of 35–50 t/ha > 70–100 t/ha > 140–200 t/ha. Broadcasting mud at 200 t/ha resulted in the growers not recovering the cost of application. Banding by-products containing mud/ash and ash at 100 t/ha or less resulted in the grower recovering the cost of the product by the second or third ratoon. By-products applied at rates as low as 50 t/ha reduced CCS, and further research is needed to improve guidelines on nutrient and water management so that growers using these by-products can maximize their profitability. © 2024, Verlag Dr. Albert Bartens KG. All rights reserved