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Population Genomics of Macrophomina spp. Reveals Cryptic Host Specialization and Evidence for Meiotic Recombination
No full textKnowledge of the factors structuring populations of pathogenic fungi is fundamental to disease management efforts and basic biology. However, this crucial information is missing for many important pathogens, including broad host range and drought-associated pathogens from the globally distributed Macrophomina genus. The objectives of this work were to evaluate the evidence for host specialization, geographic adaptation, and recombination using a global survey of Macrophomina isolates from diverse geographic, temporal, and host sources. We obtained high-quality short-read sequence data for 463 Macrophomina spp. isolates, representing four putative species, collected from 91 host plant species and soil in 23 countries. Analysis of bi-allelic, single nucleotide polymorphismsrevealed high diversity, admixture, and equal mating type ratios suggesting on-going recombination. Although most tested isolates asymptomatically colonized strawberry, only strawberry-derived isolates caused disease on this host. These isolates were all in a single lineage, suggesting the ability to cause disease on strawberry is not widespread among M. phaseolina. Significant associations were also found between isolation from soybean plants and specific population clusters, suggesting that specialization for virulence or reproduction has also occurred for soybean. Geography ? isolate genotype associations were weak, suggesting Macrophomina spp. were frequently trafficked between regions. Reference free whole genome comparisons support current boundaries among four Macrophomina species, and new molecular markers were designed to specifically identify each species. Contrary to expectations, M. phaseolina should be considered a single species with both specialist and generalist populations in which meiosis can maintain genetic diversity
Cumulative ground cover maintenance: what does it tell us about the grazing landscape and its management?
No full textTwo key challenges in rangeland management are determining the sustainability of management practices and the cumulative impact of those practices on the condition / health / productivity of the managed landscape. To this end remotely sensed cover products have been widely used in recent decades as there are no alternative products with a comparable spatiotemporal coverage and resolution.
We trialled a new approach to remotely assess land condition and management sustainability using ground cover data. The method first benchmarks Spring ground cover per pixel against local ground cover values within the land type (regional comparison (RC)). RC is a useful ground cover benchmark because it accounts for impact of land type and rainfall history on ground cover at any site. We then model Spring RC values based on the RC value of the previous Spring and recency of fire (a driver of ground cover not well accounted for by RC). We interpret the predicted quantile of any model prediction (GCM) as an index of how well the RC value has been maintained over that year at the site.
If annual GCM values do indicate how well ground cover has been maintained within the year, it is possible that long term consistency in GCM values (high or low) may highlight the broader sustainability of the management system (e.g. management that maintains ground cover probably also limits erosion and promotes desirable pasture species). Furthermore, more sustainable management systems might indicate places of high and/or improving land condition. This poster explains how the GCM layers were developed and tests the idea that they could be a useful tool to map both the historical sustainability of management systems as well as their impacts on land condition
2025 situational analysis of pasture dieback in eastern Australia
No full textPasture dieback affects millions of hectares of highly productive grazing land in eastern Australia, specifically north, central and south-eastern Queensland, and north-eastern New South Wales. The impact to grazing industries, including beef, dairy and sheep, is significant. Improved (or sown) tropical and sub-tropical grass species are predominately affected; very few native grasses are impacted. Affected plants initially exhibit leaf discolouration, which culminates in a mosaic of patches of dead grass across a pasture. Temperate grasses and broadleaf plants including annual and perennial legumes are not affected.
Dieback has occurred previously in tropical pastures across Queensland. A large dieback event happened in central Queensland during the 1990s and a much smaller and shorter event occurred in the mid-1920s in south-eastern Queensland. The leading cause of the current situation is the pasture mealybug bug (Heliococcus summervillei), whereas the cause of the 1990s event remains unknown despite research at that time. This indicates potential for a disease complex. Dieback has also been recently reported in tropical pastures across multiple south American countries where varied causes have been purported.
The Department of Primary Industries (DPI) initiated research activities into this condition in 2015 which included: characterising symptom progression, factors affecting disease occurrence, diagnostic pathology, and management options for affected areas. This research has been complimented by similar activities undertaken by other organisations. Research activities were accompanied by an industry engagement program including peer-to-peer learning activities such as group workshops and field days; and published resources including online and print factsheets, articles, videos, podcasts and social media posts. All are available in an online hub (www.futurebeef.com.au/resources/pasture-dieback/)
Legacy pasture evaluation trials delivering new persistent legume varieties
No full textPasture legumes are the best long-term option to increase productivity and profitability from grass-dominated pastures in the sub-humid, sub-tropics and tropics of Australia through improving pasture yield, diet quality and performance of livestock. However, finding legume varieties that are persistent and productive in the long-term for the climatic zone and grazing systems has been challenging.
Queensland graziers report that long-term persistence (20 to 50 years) of legumes is their highest priority trait for selecting new varieties. Legume and livestock productivity was a second order priority; other traits such as seasonality of growth, ease of establishment, seed production, and methane reduction potential were considered important but of lower priority.
Research funding cycles are typically 3 to 5 years, which means long-term persistence of legume accessions cannot be directly measured before release as new varieties. However, there is a network of old pasture evaluation trial sites in the study area which provides an important opportunity for selecting persistent varieties.
Forty-eight pasture evaluation trial sites that were sown between 1978 and 2008 were inspected across southern and central Queensland to identify legumes that persisted in the long-term. Most of the sites had been ‘abandoned’ as research trials for >10 years and generally incorporated back into the grazing property. The two outstanding genera for long-term persistence were Stylosanthes and Desmanthus with some accessions demonstrating long-term persistence across broad geographic locations.
Legume persistence at these legacy trial sites has supported new research. Accessions of legumes were described and collected from old trial sites and evaluated across six new sites in southern Queensland. Five new Stylosanthes varieties have recently been released for commercial production demonstrating better persistence and 40 to 70% higher yields (averaged across trial sites) than the best performing commercially available legume stylo varieties. On-going research is identifying persistent and productive Desmanthus accessions for potential commercialisation as new varieties
Pathways less travelled to forage legume practice change
No full textLand condition decline, pasture rundown and dieback are significant issues for beef businesses in central Queensland. Perennial pasture legumes play a role in preventing and remediating these conditions, leading to improved beef production and business profitability. Adoption of perennial legume pastures by beef producers in central Queensland is low; however, there is renewed interest in legume plantings since they have been promoted as an option for greenhouse gas reduction. An extension strategy was developed to use carbon-focused peer-to-peer learning workshops to generate interest in one-on-one support to introduce perennial pasture legumes. Workshops were delivered in three locations in central Queensland in 2023 and were designed with a mixture of group learning activities and presentations. The workshop delivery team included a carbon scientist, carbon project advisor and an experienced extension pasture specialist. Feedback collected from the workshops indicated that 10% of producer respondents intended to make a change on-property involving legume pastures on 3,387 ha. 41% of producer attendees participated in one-on-one action plan support on-property after the workshop, where a total of 16 actions plans for 2,297 ha were documented on 10 properties. In the 11 mo after the initial workshops, producers who participated in the action plan process reported 561 ha of practice change. This change was considered to be incremental towards legume planting and included practices such as soil and seed testing, timber clearing and cultivation. Despite the documented practice changes, the one-on-one support method was labour intensive. Ongoing engagement with producers is continuing into the legume-planting season, such that more data can be collected on practice change. Overall, the strategy of using carbon-focussed events to garner interest in perennial legumes and producer practice change was successful and will be repeated
Long term effects of different stocking strategies on land condition and profitabilty in a highly variable climate
No full textRainfall variability is a major challenge to sustainable grazing land management in northern Australia. We present data from a long-term grazing trial comparing the performance of different cattle stocking strategies over 27 years of highly variable rainfall. Strategies involved combinations of different stocking rates, fixed versus flexible stocking and wet season pasture spelling. Individual live weight gain (LWG) and product price were highest at moderate stocking rates applied with or without wet season spelling.
Total LWG/ha was highest at heavy stocking rates, but gross margins lowest due to reduced product value and drought feeding costs. Flexible stocking was as profitable as fixed moderate stocking but also avoided the need to destock in drought years.
Land condition as indexed by the proportion of 3P (palatable, perennial and productive) grasses declined rapidly under heavy stocking, reducing resilience and long-term carrying capacity (LTCC). Although fixed moderate stocking at LTCC initially maintained land condition, condition ultimately declined due to the failure to reduce stocking rates in droughts. Land condition also declined with drought under flexible stocking, but recovery appears greater with recent good seasons. Wet season spelling was essential to buffer drought effects and is accelerating recovery post drought.
These results show that over the long term, heavy stocking is a high risk, and ultimately an unprofitable and unsustainable strategy. Although fixed, moderate stocking strategies are lower risk, they will still lead to degradation if stocking rates are not reduced in dry years to match forage availability. We recommend that climate variability be managed using flexible stocking rates in a pro-active, risk averse manner coupled with regular wet season spelling. These should be applied adaptively based on seasonal conditions and observed responses to management actions
Should we burn or bust the biocrusts: an overview of biocrust management in the Australian rangelands
No full textThe biocrust microbiome that occupies the surfaces of rangeland soils globally are key contributors to carbon sequestration, nutrient cycling and sustain vegetation cover. Previously, research in northern Australia has demonstrated N inputs from biocrusts of 5 kg/ha seasonally that accounts for approximately one sixth to half of the annual pasture N demand. Biocrusts are important indicators of rangeland health, and we address how management actions can facilitate their survival under climatic extremes.
We explored the resilience of biocrusts to fire and grazing at two long-term research sites at Kidman Springs (NT) and Wambiana (QLD), respectively. At Kidman Springs in our first DNA analysis (metabarcoding) we examined the recovery of biocrusts after one year of burning, on plots 2 and 4 year prescribed burning regimes, carried out late dry season. Biocrusts were resilient to fire and recovered in the first wet season with no grazing pressure, as there were no differences in composition between the control and late 2- and 4-year burns. However, DNA analysis from nearby grazing exclosures showed that after 60 years of no cattle grazing, biocrust composition had significantly diverged from grazed areas. Furthermore, in our second DNA analysis (metagenomics) we included samples from 2, 4 and 6 years prescribed fires, burnt early and late in the dry season, and we collected samples at the dry and wet season, demonstrating that there was significant variation in biocrust bacterial composition between all fire treatments and soil types. Bacterial genes responsible for nitrogen fixation were sensitive indicators, that responded to seasonal conditions. Biocrusts also had significantly more nitrogen and carbon than bare degraded soil.
At Wambiana, moderate stocking rates maintained good land condition and strengthened nitrogen fixation potential of biocrusts. Key indices of landscape function including biocrust cover were informed by land condition and climatic conditions. Moderate stocking rates combined with wet season rotational spelling on average every three years also facilitated nutrient cycling. Recently, we have shown that discrimination of biocrusts using satellite imagery is a feasible monitoring tool on a landscape scale. We can track changes in ground cover including biocrusts both spatially and temporally. Bare ground covered with biocrusts are sensitive indicators of landscape function
Enhancing sorghum yield and risk management via optimizing crop design
No full textGlobally, the need to intensify food production and accelerate crop yield gains requires new strategies for crop improvement. Agricultural production outcomes, such as grain yield and crop failure risk, are complex and emerge from interactions that occur between genotype (G), crop management (M), and the environment (E) during crop growth and development. With no feasible means to assess all possibilities, these G × M × E interactions complicate crop improvement decision-making and limit our ability to enhance production over diverse environments and conditions. Further complicating this problem are productivity-risk trade-offs, which make simultaneous improvements in multiple production criteria difficult. This study introduces the CropGen platform, which offers a simulation-based approach to explore crop-adaptation landscapes to identify optimal G × M strategies, called crop designs, for target E. By connecting the Agricultural Production Systems Simulator sorghum model with an evolutionary optimization algorithm, the CropGen platform enables the exploration of crop-adaptation landscapes and the generation of optimized crop designs allowing for the trade-offs among production criteria. This study details the testing and development of the CropGen platform, including its application to a sorghum crop improvement case study in situations varying in yield potential. Findings indicate the CropGen platform is capable of generating physiologically sensible sets of Pareto-optimal solutions that represent a range of trade-offs between yield and crop failure risk. The potential for CropGen to help guide and focus research and breeding efforts for the adaptation of crop production and the advancement of crop improvement is highlighted
Northern Australia's Green Break of Season (GBOS) dates and their relationship with pasture
No full textAcross northern Australia's rangelands, livestock production depends heavily on rain-fed pastures that rely primarily on rainfall during the wet season months of October to April. Planning for the onset of pasture growth (called green cover onset) after the dry season enables graziers to set appropriate stocking rates based on the available fodder at the end of the previous growing season. This reduces costs and alleviates the strain on existing livestock. This study focuses on the 'green break of season' (GBOS) date, defined as the first occurrence of meaningful rainfall over a 3-day period after the dry season, and its relationship to the green cover onset. By utilising robust model-derived estimates and satellite observations of pasture growth at representative locations, we examine the relationship between the green cover onset and GBOS for various rainfall thresholds and find a strong linear relationship. Additionally, we investigate the historical or long-term 'green date', at which the GBOS reliably occurs in 70% of all years. We analyse the spatial distribution of green dates over northern Australia and examine how these dates are influenced by the phase of the El Niño-Southern Oscillation. Ultimately, our findings aim to assist producers and graziers in determining their "decision date" for better management of livestock and resources
From reels to research: Motivations and concerns of billfish citizen science participants
No full text1. Citizen science facilitates cost-effective ecological data collection at much larger scales than would otherwise be feasible. This is particularly useful for the study of highly migratory species with broad distributions, such as billfishes.
2. Participants in citizen science benefit from an increase in scientific literacy, a sense of satisfaction and enhanced understanding. However, there are common challenges involved in citizen science projects, including the recruitment and long-term retention of participants. Applying knowledge about participant motivations and concerns is needed to overcome these barriers.
3. We conducted an anonymous online survey of 153 game fishers from across Australia, who were largely recruited through game fishing clubs. The survey investigated their perspectives on participating in citizen science on billfish, including their motivations and concerns.
4. Overall, those surveyed were highly motivated to participate in billfish citizen science programmes and reported few barriers to their engagement in research. Alongside wanting to contribute to billfish research and management, game fishers were motivated to participate to counteractive potential negative perceptions of the sport. However, approximately one third of respondents had not participated in research. Therefore, opportunities for further recruitment exist as potential participants almost certainly exceed current participants. Impediments to participation included a lack of communication about opportunities and outcomes of citizen science research.
5. The survey highlighted a need to strengthen citizen science programmes to ensure participant retention and recruitment through targeted engagement and collaboration across organisations, which includes harnessing technology. Improved communication about the purpose and outcomes of research is key. We anticipate that our findings and recommendations are applicable to broader citizen science programmes, particularly those involving recreational fishers or a specialised pool of highly motivated participants.
6. Great opportunity exists for researchers, fisheries managers and fishing organisations to work together to expand citizen science programmes that strategically improve our knowledge of the biology and stocks of billfish and other recreationally important fish species