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The core fungal microbiome of banana (Musa spp.)
No full textHere, we report a metabarcoding (ITS2) study to define the common core fungal microbiome (mycobiome) of healthy Musa spp. (bananas and plantains). To identify a list of 21 core fungal taxa, we first characterised the effects of edaphic conditions and host genotype – two factors that are likely to differ between farms – on the diversity of fungal communities in bulk soil and seven plant compartments. This experiment facilitated shortlisting of core ‘candidates’, which were then elevated to full core status if also found to frequent a wide-range of field-grown Musa spp. and exhibit hub-like characteristics in network analyses. Subsequently, we conducted a meta-analysis of eleven publicly available datasets of Musa spp. associated fungi demonstrating that the core fungi identified in our study have close relatives in other countries. The diversity and composition of mycobiomes differed between plant compartments and soils, but not genotypes. The core mycobiome included Fusarium oxysporum and its relatives, which dominated all plant compartments, as well as members of the Sordariomycetes , Dothideomycetes , and Mortierellomycota . Our study provides a robust list of common core fungal taxa for Musa spp. Further studies may consider how changes in the frequencies and activities of these taxa influence host fitness and whether they can be managed to improve banana production
Natural durability of mid-rotation plantation Gympie messmate and red mahogany in a 13-year aboveground field test
No full textCompared with the same species from native forests, faster growth and earlier harvesting of plantation timber may cause reductions in heartwood extractive levels, density and decay resistance due to the immaturity of wood tissues. The aim of this study was to evaluate the decay resistance of mid-rotation plantation Gympie messmate and red mahogany heartwood in ground proximity and L-joint aboveground field tests at three sites in Queensland, Australia. After 12-13 years in both tests, the inner heartwood of each plantation species generally had more decay than the middle and outer heartwood. Middle heartwood was significantly less durable than outer heartwood for each plantation species in the ground-proximity test at the tropical South Johnstone site. Plantation Gympie messmate outer heartwood performed similarly to native-forest spotted gum, the high-durability reference species. Plantation red mahogany had more decay than Gympie messmate. Given the need for plantation timber to supplement supplies from sustainable native forest resources, substantial research is recommended to fully characterise the durability of key plantation hardwood species, including investigation of protective treatment supplementation and communication of design requirements
Reproductive performance of northern Australia beef herds. 1. Survey of nutritional, breeding and herd health management practices and of the environment
Get PDFData concerning the practices and policies of collaborating properties for nutritional, breeding and health management of herds were captured by survey of herd owners/managers (n = 78) at the commencement of a large observational study conducted across northern Australia to identify and quantify the effect of major animal-, management group- and property-level risk factors on measures of reproductive performance. The cooperating herds in this study were considered to be broadly representative of north Australian beef breeding enterprises in terms of geography, size and ownership. Using four broad regional categories, this paper presents descriptive summaries of the management practices and nutritional conditions of cooperating herds in what was known as the Cash Cow project. Property sizes were largest within the Northern Downs and Northern Forest, and smallest within the Southern Forest. The expected average annual growth of yearling steers was >50 kg less in the Northern Forest, compared with the other country types, which also appeared to be associated with the identified production system and turnoff animal. Despite the exacerbated nutrition and environmental challenges and likely increased time required for new managers within the Northern Forest to attain an in depth understanding of the cattle and property dynamics, this region had the greatest incidence of management changes. The nutritional information summarised in this study highlights that available phosphorus during the wet season, as indicated by faecal levels in proportion to dietary energy, was likely to limit animal production within the Northern Downs and Northern Forest. During the dry season, pasture digestibilty and protein levels were likely to be approaching maintenance for cows on ~50% of properties in each country type and that responses to rumen degradable protein were also likely on 50% of properties. Despite this finding, low use of dry season supplements was observed for the Northern Downs, which was partially explained by the high incidence of the management systems based on segregating cows on lactation status and pregnancy. In all country types, the ratio of bulls to cows was higher than the 2.5% recommended for extensively managed situations, while limited use of vaccines to control infectious causes of reproductive loss was also observed. The major conclusion of this study is that there was marked variation in the adaption of interventions to specific businesses, indicating considerable opportunity exists for further adaptation in the region
A cross-scale analysis to understand and quantify the effects of photosynthetic enhancement on crop growth and yield across environments
Get PDFPhotosynthetic manipulation provides new opportunities for enhancing crop yield. However, understanding and quantifying the importance of individual and multiple manipulations on the seasonal biomass growth and yield performance of target crops across variable production environments is limited. Using a state-of-the-art cross-scale model in the APSIM platform we predicted the impact of altering photosynthesis on the enzyme-limited (Ac) and electron transport-limited (Aj) rates, seasonal dynamics in canopy photosynthesis, biomass growth, and yield formation via large multiyear-by-location crop growth simulations. A broad list of promising strategies to improve photosynthesis for C3 wheat and C4 sorghum were simulated. In the top decile of seasonal outcomes, yield gains were predicted to be modest, ranging between 0% and 8%, depending on the manipulation and crop type. We report how photosynthetic enhancement can affect the timing and severity of water and nitrogen stress on the growing crop, resulting in nonintuitive seasonal crop dynamics and yield outcomes. We predicted that strategies enhancing Ac alone generate more consistent but smaller yield gains across all water and nitrogen environments, Aj enhancement alone generates larger gains but is undesirable in more marginal environments. Large increases in both Ac and Aj generate the highest gains across all environments. Yield outcomes of the tested manipulation strategies were predicted and compared for realistic Australian wheat and sorghum production. This study uniquely unpacks complex cross-scale interactions between photosynthesis and seasonal crop dynamics and improves understanding and quantification of the potential impact of photosynthesis traits (or lack of it) for crop improvement research
A robust field-based method to screen heat tolerance in wheat
No full textWheat is highly sensitive to heat shocks and their timing. Hence, field-based ranking for heat tolerance may be confounded by phenological variations at the time of heat events. A photoperiod-extension method (PEM) was developed, allowing screening of wheat genotypes at matched developmental stages despite phenological variations. Paired trials were conducted to compare PEM and conventional field screening. In the PEM, artificial lighting was installed at one end of each row, inducing a gradient of flowering times. Individual stems or plot quadrats of each genotype were tagged at flowering. Late-sown plants experienced significantly more heat and greater grain yield reductions than early sown plants. Strong correlations between trials experiencing a similar degree of heat were found both for individual grain weight (IGW) and total grain weight with the PEM, either with individual stem tagging or quadrat tagging. By contrast, correlations for IGW and yield in these environments were either poor or negative for conventional trials. With the PEM, strong genetic correlations were found between irrigated environments of similar heat stress, with respective r correlations ranged from 0.46 to 0.8 for IGW; and 0.54–0.75 for total grain weight. By contrast these correlations were substantially weaker for conventional yield plots (average r values ranged from 0.11 to 0.53 for IGW; and 0.05–0.36 for grain yield. The quadrat sampling appeared overall more suitable for high-throughput phenotyping. The method promises to improve the efficiency of heat tolerance field screening, particularly when comparing genotypes of different maturity types
Weed biological control in Zimbabwe: Challenges and future prospects
No full textIn Zimbabwe, the structure and integrity of various ecosystems is rapidly deteriorating, in part due to invasive alien plants. While there is recognition of the challenges posed by invasive alien plants and the complexity surrounding their successful management, very little has been done, documented or evaluated in the country recently, including classical weed biological control activities. We review the current status of invasive alien plants and classical weed biological control in Zimbabwe especially their management and legislation governing this management. We record the presence and distribution of weed biological control agents currently in Zimbabwe. The Biological Control Target Selection (BCTS) system was used to identify invasive plant species in Zimbabwe that could benefit from on-going or new classical biological control programmes. While biological control has been implemented in the country since the 1960s, and significant control has been achieved on floating aquatic macrophytes, no biological agent has been released on a terrestrial weed since 1961. However, 10 agents released in neighbouring South Africa have spread naturally into the country on contiguous plant populations and some are providing gratuitous control of some of the weeds. We identified 19 invasive alien plants that could be successfully managed through classical weed biological control, and for 12 of these, this could be achieved at minimal cost, as agents are available within the region. Zimbabwe, perhaps with the help of international aid organisations investing in the region, could: a) conduct extensive surveys of established biological control agents already present in the country; b) redistribute these agents into areas of the country where they are not already present and foster those spreading north in South Africa and likely to arrive eventually through natural spread, and; c) initiate new weed biological control programmes against new targets by importing new agents available from South Africa or Australia
Investigating Factors Influencing Rolling Shear Performance of Australian CLT Feedstock
Get PDFThis paper presents an investigation on the influence of various factors on rolling shear (RS) properties of timber feedstock for cross laminated timber (CLT) available from Australian plantation forest resources. Comparison of RS properties between three softwood species namely southern pine, radiata pine and hoop pine are presented. Furthermore, the effect of modulus of elasticity (MOE), equilibrium moisture content (EMC), aspect ratio, knots and projection length on rolling shear behaviour were investigated. Mean RS modulus for radiata pine, southern pine and hoop pine samples were 74.7 MPa, 87.1 MPa and 99.7 MPa, whilst the RS strength of those species were 2.6 MPa, 3.1 MPa and 3.7 MPa, respectively. Radiata pine samples exhibited the lowest values for RS modulus and strength, almost 30% less than those of hoop pine samples. The study confirmed that the density and MOE had a very weak correlation with RS properties for all pine species. There was an obvious decrease in RS modulus (by 18%) when the woods’ conditioned EMC changed from 8% to 12%. A further 33% decrease was observed when the woods’ conditioned EMC increased from 12% to 16%. However, the percentage increase in RS strength was found to be 23% higher in wood with 12% conditioned EMC while compared against wood conditioned to 16% EMC. RS strength improved with increased aspect ratio; however, RS modulus remained almost unaffected. Moreover, the projection length that resulted in the load passing through the centroid of the specimen resulted in lower RS modulus values, but the presence of knots improved both RS strength and modulus for all three tested species
Differential olfactory responses associated with host plant shift by the fruit-piercing moth, Eudocima phalonia, in the Pacific islands
Get PDFThe fruit-piercing moth (FPM) Eudocima phalonia is widely present in the tropics, causing major damages to the citrus industry. In its ancestral distribution range, e.g. Australia, FPM develops on vines from the Menispermaceae family. But in more recently colonized islands, e.g. New Caledonia, FPM populations have shifted to new host plants of the Fabaceae family, Erythrina spp.. To understand this host shift, we studied the chemical ecology of FPM as a mechanism driving host plant acceptance. We collected volatile headspace samples of Erythrina species and Menispermaceae and compared their chemical spectra. We assessed the electrophysiological responses of FPM populations from the two countries to the plant chemical extracts and identified bioactive compounds. The volatile profiles from each species were quite different between and within each plant family. However, five compounds common across the two families triggered electrophysiological responses in both FPM populations. Those common bioactive compounds could have facilitated the host shift to completely different plant family. Furthermore, the diverging history between the two FPM populations may explain differences in electrophysiological sensitivity to other specific compounds. These results are discussed in the context of the production of a generic lure that could be attractive to all FPM populations
Soybean Production Manual: A complete guide to growing soybean in Australia. [online]
No full textThe online manual, adapted from the ‘Better Soybean Training Manual’, is part of the joint initiative aimed at supporting the expansion of the Australian soybean industry by providing updated soybean training and technical resources to Australian growers and agronomists. There are ten modules: 1) marketing, 2) rotation and variety choice, 3) crop nutrition, 4) plant growth and development, 5) agronomy, 6) weed management, 7) disease management, 8) pest management, 9) harvesting, and 10) safe storag
Capturing episodic impacts of environmental signals
Get PDFEnvironmental scientists frequently rely on time series of explanatory variables to explain their impact on an important response variable. However, sometimes, researchers are less interested in raw observations of an explanatory variable than in derived indices induced by episodes embedded in its time series. Often these episodes are intermittent, occur within a specific limited memory, persist for varying durations, at varying levels of intensity, and overlap important periods with respect to the response variable. We develop a generic, parametrised, family of weighted indices extracted from an environmental signal called IMPIT indices. To facilitate their construction and calibration, we developed a user-friendly app in Shiny R referred to as IMPIT−a. We construct examples of IMPIT indices extracted from the Southern Oscillation Index and sea surface temperature signals. We illustrate their applications to two fished species in Queensland waters (i.e., snapper and saucer scallop) and wheat yield in New South Wales