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Puccinia punctiformis as a biocontrol agent for Cirsium arvense: effect of biotic and abiotic factors on success of infection : A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Applied Science at Lincoln University
Get PDFCalifornian thistle (Cirsium arvense L. (Scop.)) is a weed in pastures and cropping systems. The fungal biocontrol agent Puccinia punctiformis (F. Strauss) Röhl. performs inconsistently on C. arvense. P. punctiformis establishment and control of C. arvense may be attributable to differing plant endophytic populations in various environments. Therefore, a study on endophytic populations within leaf, stem, and root tissue of C. arvense was undertaken with seasonal dynamics and location considered.
Ninety-one endophytic genera, of which 68 not previously known to be associated with C. arvense, were ascertained in this study by culturing methods. To determine the identity of these cultures, PCR with fungal specific primers was performed, followed by sequencing and identification of the PCR products. Endophytic communities of stems and leaves of C. arvense are dynamic, with changes in community composition occurring over seasons. In autumn, a significant increase in leaf endophytic diversity occurred, which may be affected by C. arvense shoots commencing die-off. Root endophytic communities were stable, with no significant changes in endophytic community composition nor diversity occurring. Leaf endophytic diversity was comparable between sites, but community composition differed. This study shows that endophytic communities are dynamic being season, site, and tissue dependent.
To enable quantification of P. punctiformis in samples, several comparisons were undertaken to finetune the qPCR assay and determine its robustness. Results were categorised in the following concentration bands: P. punctiformis absent; low concentration present (100 ng/µL). An efficiency correction would be applied to add to the quality of results obtained.
To determine the effect of endophytes on P. punctiformis urediniospores infection, two genotypes of C. arvense were grown in either in a controlled environment glasshouse, as potted plants in a potting mix media, or under natural, field conditions in soil. Establishment of P. punctiformis and endophytic communities were compared between genotypes (G27 and F1) and growing conditions (glasshouse and field) by visual estimation as well as quantitative PCR for the presence of P. punctiformis. The number of endophytic genera as well as community composition were determined prior to trial commencement and on completion. Six weeks post-inoculation, G27 plants had higher levels of disease expression in the field compared to plants of the same genotype in the glasshouse (70% vs 20%, 23 vs 10 ng/µL, respectively; P<0.001). Whereas, F1 genotype showed greater infection severity under glasshouse conditions than in the field (46% vs 45%, 75 vs 1 ng/µL, respectively; P<0.001). Endophyte community composition was compared between least and most infected leaves of these plants. In a second study, endophytic populations were compared in symptomatic and asymptomatic shoots from a field with systemic rust infection. From these studies, some genera which may enhance P. punctiformis infection were identified. These included: Bipolaris, Curvularia, Gliocladiopsis, Leptosphaeria, Phoma, Phaebotryosphaeria, Septoria, and Septoriella.
To determine the optimal urediniospores concentration and the effect of abiotic factors on P. punctiformis urediniospores infection, four duplicate pot trials were performed. Spore concentrations ranging from 0.1-0.4 mg/mL effectively established P. punctiformis infection. A selection of positively charged compounds (chitosan, and four nitrogen fertilisers) were trialled, with none enhancing P. punctiformis infection. Despite this study not identifying a method to enhance P. punctiformis infection, it has contributed to the knowledge on C. arvense endophytes. Further research could explore if the genera found in highly infected leaves of C. arvense could be used to enhance P. punctiformis infection
Quantifying erosion rates and weathering pathways that maximize soil organic carbon storage
Get PDFPrimary minerals that enter soils through bedrock weathering and atmospheric deposition can generate poorly crystalline minerals (PCM) that preferentially associate with soil organic carbon (SOC). These associations hinder microbial decomposition and the release of CO₂ from soils to the atmosphere, making them a critical geochemical control on terrestrial carbon abundance and persistence. Studies that explore these relationships are typically derived from soil chronosequences that experience negligible erosion and thus do not readily translate to eroding landscapes. Here, we propose a theoretical framework to estimate steady-state PCM density and stocks for hilly and mountainous settings by coupling geochemical and geomorphic mass balance equations that account for soil production from bedrock and dust, soil erosion, PCM formation from weathering, and the transformation of PCMs into crystalline phases. We calculate an optimal erosion rate for maximum PCM abundance that arises because PCMs are limited by insufficient weathering at faster erosion rates and loss via “ripening” into more crystalline forms at slower erosion rates. The optimal erosion rate for modeled hilltop soil is modulated by reaction rate constants that govern the efficiency of primary mineral weathering and PCM ripening. By comparing our analysis with global compilations of erosion and soil production rates derived from cosmogenic nuclides, we show that landscapes with slow-to-moderate erosion rates may be optimal for harboring abundant PCM stocks that can facilitate SOC sequestration and limit turnover. Given the growing array of erosion-topography metrics and the widespread availability of high-resolution topographic data, our framework demonstrates how weathering and critical zone processes can be coupled to inform landscape prioritization for persistent SOC storage potential across a broad range of spatial and temporal scales
No cow? Understanding US consumer preferences for plant-based over regular milk-based products
Get PDFDairy products such as cheese, butter, and yoghurt are popular staples in American households; however, alternative plant-based products are gaining increasing popularity. An online survey was conducted to investigate the factors that determine US consumers’ preferences for plant-based and regular milk-based products before and since the occurrence of food price inflation. The study used descriptive statistics and partial least square structural equation modelling for the analysis. The accessibility of plant-based substitutes, the perceived impact of food price inflation and associated consumer behaviour, engagement with food-related activities, and environmental concerns were important factors in both scenarios. Recommendations to marketers on how to target different consumer groups are offered
Altering the probiotic epigneome, its potential application in fermentation
No full textEpigenetics is the study of changes in gene expression and function that occur without a change in the underlying DNA sequence. These changes in humans, can be caused by a variety of factors, including dietary intake, environmental exposures, and lifestyle factors. Epigenetic modifications, such as DNA methylation and histone modifications, can turn genes on or off and affect the expression of certain proteins. However, epigenetics also has great potential for interdisciplinary applications, including in the fields of microbiology and fermentation science. This study aimed to investigate the impact of certain human dietary compounds on probiotic strains which also present in the gut, specifically focusing on Lactobacillus acidophilus, and to apply the acquired knowledge to enhance the effectiveness of probiotic strains used in fermentation processes. The study explored epigenetic effects of six dietary compounds on the target probiotic strains. These compounds were compared to a known DNA methyltransferase inhibitor, 5-aza-2’-deoxycytidine, as a positive control. The microbial epigenetic effects were evaluated using whole genome bisulphite sequencing, RNA sequencing, and metabolomic profiling. The results show that each dietary compound has a unique epigenetic-based impact on regulation of gene expression in L. acidophilus. The study also investigates the application of epigenetically-modified probiotics in milk fermentation to develop a novel probiotic yogurt that could provide additional functional benefits in the gut and overall health benefits to the body
The role of information in land-use decision-making : The perspective of farmers in New Zealand : A thesis submitted in partial fulfilment of the requirements for the Degree of Master at Lincoln University
No full textAgri-food systems are facing increasing pressure to transition toward more sustainable alternatives, which are information-intensive and may require different forms of knowledge. Therefore, optimal and sustainable land-use decision-making requires effective information provision. However, digital technologies and the information age have changed the ways in which farmers interact with information. This necessitates different approaches and raises questions regarding how and why farmers gather information and whom they trust. Thus, the purpose of this study was to explore the role of information in land-use decision-making from the perspective of farmers in New Zealand. Twenty-two semi-structured interviews with commercial pastoral farmers and a focus group with emerging young farmers were conducted.
The results evidence that information is important for decision-making and that gathering processes are personal and contextual. The farmer participants sourced information from a variety of sources across digital and physical formats. Traditional institutions (i.e., industry groups) were recognised; however, digital and informal sources (i.e., the internet and interpersonal networks) were the most utilised. The farmer participants engaged as researchers and information curators online and within networks, to share learnings in communities of practice. The young farmer participants particularly interacted digitally, following farmer influencers and utilising artificial intelligence (AI). Audio formats were acknowledged as useful, and information about consumers was important, signalling market orientation. Combining formal and informal elements, the farmer participants valued how catchment groups are community-led and outcomes-focused. Additionally, knowledge brokering through intermediaries at the catchment level assisted with information exchanges.
The most trusted sources of information were other high-achieving farmers and interpersonal networks; however, there were mixed experiences with peers. Validation of information occurred through a triangulation and cross-referencing process. Attempts to determine what is trustworthy were challenging due to misinformation and information overload, which hindered effective decision-making. Farmers largely felt that strategic land-use information was challenging to source, especially in relation to regional contexts.
Overall, the results signal the need to combine the best of informal and formal sources and that farmers should be recognised as co-creators of information. This research contributes to the literature on information and farmer decision-making in the information age. Potential actions that emerge from the findings include improving digital literacy, hybrid approaches to information provision, adopting listening rather than telling approaches, and supporting intermediaries. These insights could be of interest to inform effective approaches to information provision. Future research into digital literacy, the perspectives of information providers, and the influence of evolving sources (i.e., AI) would be useful. Additionally, the implications of misinformation and information disorders on trust and decision-making should be considered. It is concluded that as technologies evolve, an ongoing conceptualisation of information and farmer habits will be required
Climate-smart agricultural practices and sustainable agrifood production
No full textThis presentation explained how adopting climate-smart agricultural practices, including minimum tillage, improved rice varieties, farmyard manure, water-saving technology, and bio-pesticides, addressed climate change issues, increased rice yields and contributed to national and global food security
A review of pasture yields and growth rates in Northland
No full textPastoral grazing is the major land use in Northland, New Zealand. This study analysed the distribution and variability of pasture dry matter (DM) yields across four distinct physiographic regions, using published and original unpublished datasets collected from 1958–2021. Dargaville had the highest mean annual pasture yield of 11900 kg DM/ha, Kaitaia 9970 kg DM/ha and Kaikohe and Whangarei at ∼8400 kgDM/ha. Pasture water use (DM yield/mm rainfall) ranged from 10.8 kg DM/mm/ha (Kaikohe) to 16.4 kg DM/mm/ha (Dargaville). Kaitaia showed the largest annual yield variability (>2300 kg DM/ha). The relationship between pasture growth and temperature was quantified to estimate temperature adjusted growth rates for these regions. Whangarei spring growth was low at 3.19 kg DM/°Cd before it declined after 2560°Cd, or ∼7630 kg DM/ha, to 1.85 kg DM/°Cd, due to summer dry conditions. These results suggest pasture production was low compared with other regions of New Zealand. The low production and persistence may be compounded by the lack of readily available supplementary feed during summer dry or winter wet conditions. This increases the risk of overgrazing which reduces plant reserves and total light interception which results in physical damage to pasture plants and lower than potential yields
Bioavailable iron concentrations regulate phytoplankton growth and bloom formation in low-nutrient lakes
No full textThe growth of phytoplankton in lakes is thought to be primarily controlled by macronutrient concentrations, but the availability of trace metal micronutrients, such as iron (Fe), are increasingly recognised as important regulators of lake primary production. This study evaluates the role of Fe in regulating phytoplankton growth in lakes of different nutrient status in New Zealand. The results of this unique year-long study, combining highly sensitive trace metal concentration analysis of waters and particulates with advanced trace metal bioavailability and speciation modelling, constrains thresholds for bioavailable Fe and colloidal Fe of 0.8 nmol·L¯¹and 30 nmol·L¯¹, respectively, below which phytoplankton growth-limitation occurs. These thresholds specifically control diatom bloom formation and termination in lakes, thereby exerting a strong influence on freshwater carbon sequestration, given the dominance of diatoms in lake bloom assemblages. Importantly, potentially toxic cyanobacteria thrived only after events of bottom water anoxia, when additional dissolved Fe in concentrations ≥4 nmol·L¯¹ was released into the water column. These new thresholds for bioavailable and colloidal Fe offer the potential to manage micronutrient levels in lakes for the purpose of regulating algal bloom formation and carbon sequestration, while at the same time, suppressing the formation of harmful cyanobacterial blooms
Report and recommendation of the review panel: Severe Weather Emergency Recovery (Resource Management—Burning of Waste) Order 2023
No full textThe draft Order proposes that the open air burning of cyclone and flood waste be a permitted activity in the Hawkes Bay and Te Tairāwhiti regions, from 27 June to 1 November 2023. To achieve this, the draft Order proposes temporary changes to the Resource Management Act 1991 (RMA), the Resource Management (National Environmental Standards for Air Quality) Regulations 2004(NES-AQ), and relevant plans. The Report concludes the Panel had not been given enough information to conclude that the draft Order is either necessary or desirable
Genetic diversity and virulence variability in Diplodia mutila isolates from symptomatic grapevines in New Zealand: Virulence and genetic diversity of Diplodia mutila
No full textGenetic diversity and virulence variability of Diplodia mutila isolates recovered from grapevines in New Zealand were investigated. The universally primed PCR (UP‐PCR) and vegetative compatibility group (VCG) methods were used to investigate the genetic diversity. Pathogenicity tests with ‘Sauvignon Blanc’ detached shoots and potted vines were used to determine the virulence diversity. UP‐PCR analysis determined eight genetic groups of D. mutila with 70% of the population within one group. Phylogenetic analysis also determined that New Zealand isolates were more closely related to Australian isolates than Californian isolates. Vegetative compatibility grouping analysis placed the isolates into three VCG groups with 57% of isolates belonging to all three VCGs. Vegetative compatibility reactions were observed among isolates, but this was not correlated with the genetic clustering. Virulence assays proved that all isolates tested were pathogenic on grapevine stems. Differences in necrotic lesions lengths caused by D. mutila isolates were identified, indicating different virulence levels among isolates, however, no relationship was found between the genetic groups and the virulence. The results of the study indicated movement of D. mutila isolates between nurseries, vineyards, and other sources in New Zealand. This information will inform control strategies to limit the further spread of this pathogen into vineyards in the same region or new regions