Doctoral (PhD) Theses

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Theses submitted by Lincoln University doctoral students.

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Effects of extrinsic characteristics, mental simulation and repetitive exposure on the hedonic, emotional and physiological responses of consumers: A study of food choices and purchasing behaviours : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2024) Mehta, Annu
In the globalization era, a multitude of new products enter the market annually. Due to the similarity in sensory properties and prices, innovators need more than traditional sensory methods to ensure product success in the market. Researchers, therefore, must understand the holistic product experience and its influence on consumer preferences. Food choices are a multi-dimensional variable influenced by physiological and psychological factors such as memory, mental simulation, sociocultural aspects, and extrinsic/intrinsic product characteristics. Consequently, food choices and purchase decisions are shaped by the multisensory information derived from products in supermarkets. The intrinsic attributes such as taste, texture, and mouthfeel perception also play a pivotal role in shaping product liking. Moreover, consumer behaviours and familiarity with novel products further influence product liking and acceptance. Therefore, this thesis’s primary aim is to comprehensively evaluate the factors influencing consumer food choices and approach-based behaviours, covering the entire spectrum from the initial encounter with a product to consumption. Additionally, the thesis aims to explore how systematic familiarization with novel products, achieved through increased awareness and repeated tasting, enhances consumer intention to try such products, thereby impacting food preferences. The impact of extrinsic attributes such as product positioning, packaging material, country of origin (COO) logo, nutritional information, and price tags on consumers’ visual attention, emotional responses, and subsequent behaviours within the supermarket setting were investigated. The study was conducted in three stages: an orientation phase for an initial overview of products, an evaluation stage where consumers individually assessed products to decipher extrinsic factors, and a final validation stage where consumers responded to attitudinal questions regarding the importance of packaging attributes. Sensory, emotional, and biometric (eye tracking and facial expressions) measurements were used to capture the consumer perception journey. The heat map results show that consumers focus their attention on products positioned at the top and centre of the supermarket shelves during the orientation stage. Glass and plastic bottles received the highest fixation count compared to other packaging types. While scanning the supermarket shelf, as indicated by Time to First Fixation (TTFF in ms), participants initially glanced at the tetra pack (3.53 ms) before shifting their attention to glass (5.23 ms). Implicit emotions provided a deeper understanding of consumers’ preferences. Principal Component Analysis (PCA) revealed an association between TTFF, engagement, and implicit negative emotions (fear, disgust, anger, and sadness) with tetra pack, tetra pack L (L stands for packaging with country-of-origin label), and pouch L. Conversely, the positive implicit emotion “joy” was associated with glass L. During the individual packaging evaluation stage, nutritional information received the highest fixation count compared to the NZ-made logo, but the NZ-made logo drove purchase intention. The study revealed that the packaging that attracted the maximum attention was not necessarily the one with the highest liking score. The consumers did not allocated significant visual attention to the price attribute despite reporting them as important factors. The study further explores how packaging attributes, such as packaging material and font colour, shape expectations and influence consumers’ approach-based behaviours, including acceptability and purchase intention. The participants evaluated tetra packs, pouches, glass, and plastic bottles using orange and white font colours in blind (tasting juice without information), expectation (evaluating packaging, no tasting), and informed (tasting juice with packaging) sessions. This analysis extends to the subsequent confirmation of these expectations after the product is tasted. The study’s results proved that packaging significantly raises expectations regarding the sensory properties of the juice. The participants perceived juice packaged in glass bottles to be fresher than plastic bottles, pouches, and tetra packs, regardless of packaging font colour. Participants had higher expectations of freshness and overall liking, which were not fulfilled during the informed session, leading to an assimilation effect. Participants penalized juice from the glass-orange bottles and tetra pack-white with declines in the liking scores, citing insufficient sourness. No penalty in liking scores was observed for the tetra pack in the informed session. Negative emotions such as "worried", "bored", and "sad" had negatively impacted approach-based behaviour in the expectation session, while positive emotions such as "happy", "enthusiastic", and "joyful" in the informed sessions positively influenced purchase intention. Therefore, marketers and product designers should prioritize understanding the overall product experience and create packaging that captures visual attention, satisfies consumers’ expectations, and evokes emotional responses, ultimately influencing consumer approach-based behaviours. The research also delves into the influence of initial awareness and repeated exposure on consumer attitudes and behaviour toward novel products, using SCOBY (Symbiotic Culture of Bacteria and Yeast) ice cream as an illustrative example. The study was conducted in three steps: a survey and two tasting sessions. The survey aimed to introduce the health benefits of SCOBY and kombucha while examining consumer attitudes and acceptance towards the novel product (SCOBY ice cream). It utilized the primary constructs (attitude, subjective norms, and perceived behavioural control) of the theory of planned behaviour (TPB) and additional constructs (emotions and food neophobia) to gain comprehensive insights into consumer behaviours. In the survey, participants who confirmed their participation in the tasting sessions were invited for blind tasting (without information) and informed tasting (with information). The study also explored the impact of the SCOBY addition in the ice cream on the texture and mouthfeel perception by measuring the particle size, tribology, and temporal dominance of sensation. In the case of a novel product such as SCOBY ice cream, initial exposure, or awareness significantly impacts consumer's attitudes and intentions to try the product. The study proved that the primary constructs of TPB significantly predicted the intention to consume SCOBY ice cream. Additionally, incorporating emotions into the constructs increased the model’s explanatory power. Attitudes, subjective norms, and emotions were the main predictors of intention, while intention and perceived behavioural control were the main predictors of behaviour. Participants’ beliefs about the safety and taste of SCOBY ice cream were significantly correlated with their intention to try the product, as were the opinions of nutritionists/dietitians, friends, and family. Overall, the model explained 21.7% of the variance in behaviour and 57.4% of the variance in intention, offering valuable insights for shaping marketing strategies for waste-to-value-added products such as SCOBY ice cream. Moreover, repeated tasting of the SCOBY ice cream after the survey significantly impacts the attitude and intention to try the novel product. Compared to the survey, there was a significant improvement in participants’ attitudes toward consuming SCOBY ice cream in tasting sessions 1 and 2. Similarly, the intention to consume SCOBY ice cream significantly increased in tasting session 2 compared to the survey and tasting session 1. Moreover, there was a significant increase in liking scores for flavour, sweetness, texture, and overall liking in tasting session 2 compared to 1. Sensory attributes such as flavour and texture, along with positive emotions such as “happy”, “pleasant”, and “interested” significantly influenced purchase intention. The study’s results suggest that repeated exposure to novel products enhances consumer acceptance and emotional responses, diverging from traditional sensory study approaches. This highlights the potential success of strategies involving repeated tasting exposure. By prioritizing the improvement of familiarity with sensory attributes such as flavour and texture, companies can positively influence purchase intention and the successful integration of innovative products into the market. Additionally, the impact of ice cream texture and mouthfeel perception on consumer preferences were further explored by measuring particle size, texture, tribological properties and temporal dominance of sensation of three samples: SCOBY ice cream and two reference samples (control and guar gum ice cream). SCOBY ice cream contains probiotics content (5.48 cfu/ml), low pH (5.50), and high titratable acidity (3.11%) than reference samples. The addition of SCOBY increased hardness (22.05 N). The frictional factor (µ) at 37˚ C was positively associated with the melting rate, grainy and thin/fluid perception while negatively correlated to firmness, smooth perception and mouthfeel liking. Additionally, the mouthfeel liking was positively related to firmness, mouth/residual coating and smooth perception while negatively associated with grainy and thin/fluid perception. The findings improve our understanding of the textural dynamics of ice cream formulations incorporating SCOBY and its impact on consumer preferences and overall liking, highlighting the importance of product characteristics in novel products. To conclude, the study underscores the significance of extrinsic attributes in shaping consumer attention and forming product expectations, influencing approach-based behaviours. Transparent packaging, such as glass and plastic bottles, elicited more positive expectations and emotions than opaque packaging, affecting consumer liking and purchase decisions. Additionally, nutritional information and country-of-origin logos played crucial roles in influencing visual attention and purchasing behaviours, showcasing the importance of provenance. Implicit and explicit emotions interacted with packaging and elicited distinct responses that affected consumers’ purchase intentions, providing a comprehensive understanding of consumer behaviour. Additionally, repeated tasting positively influenced attitudes and intentions to try novel products, underscoring the importance of consumer education in product acceptance. Sensory attributes such as texture and flavour significantly influenced product liking, highlighting the strategic importance of understanding consumer psychology and fostering positive sensory experiences for the success of innovative food products.
Embargo
A trajectory of financial inclusion: An empirical analysis of Ghana households : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2024) Saka, Abraham Nii Adoteye
The need for a paradigm shift towards inclusive growth has recently received increased attention from governments and policy-makers. Financial inclusion plays a central role in inclusive growth. This is because financial inclusion is an enabler of economic growth, poverty reduction, income inequality reduction and women empowerment, especially in developing countries such as Ghana. Notwithstanding these benefits, the level of financial inclusion in Ghana is low. The World Bank provides a roadmap (the gateway to financial inclusion) on how to move people from being unserved (financial exclusion) to being served (financial inclusion). This roadmap highlights the need for households to have access to formal financial services such as payments, credit, savings, insurance, and remittances. This means that measuring the level of a country’s financial inclusion must include these services for it to be representative. Previous studies focused on banks and neglected other financial intermediaries, such as insurance companies (insurance financial services) in creating a financial inclusion index to measure a country’s level of financial inclusion. This study includes insurance in creating a financial inclusion index for Ghana for our study period (1980 to 2021) to find that there have been improvements in the level of financial inclusion during that time. This suggests that several financial sector reform programmes implemented in Ghana, as well as legal and regulatory reforms in the banking and insurance sectors, have had a positive impact on financial inclusion in Ghana. The financial inclusion score average was 0.25 for Ghana for the study period, which categorizes Ghana as a low financial inclusion country per Sarma’s (2008; 2012) categorization. Overall, however, the upward trend in financial inclusion in Ghana during the study period is an encouraging sign for the push to ensure all Ghanaian households are financially included. The study investigates what factors drive financial inclusion in Ghana and finds financial inclusion has a positive, significant relationship with GNI per capita and MSCPS in Ghana. Conversely, the study finds a negative relationship between financial inclusion and the real effective exchange rate. Government spending, inflation and money supply are negatively but insignificantly related to the level of financial inclusion in Ghana. Finally, I find that insurance and financial service imports (positive), urbanization (positive), mobile money availability (positive), fixed telephone ownership (negative), and remittances (positive) had no influence on the level of financial inclusion in Ghana during the study period. The literature suggests that there is no consensus on the direction of the relationship between financial inclusion, poverty and income inequality. To investigate the direction of the relationship for Ghana, the study runs an ordinary least square multiple regression using household consumption (a proxy for poverty) as the dependent variable, which is regressed against several independent factors including our comprehensive financial inclusion index. I find that level of financial inclusion, which averages 0.25, did not improve household consumption (reduce the prevalence of household poverty) in Ghana during the study period. A possible explanation could be the structure of the financial system of Ghana is not well-developed and financially included (Ghana is classified as low financial inclusion country with an average financial inclusion score of 0.25) to reach majority of the households (especially poorer individuals and households) to effectively reduce the prevalence of poverty in Ghana positively. The ineffectiveness of the financial sector in the allocation of funds causes low labour productivity, which increases the prevalence of poverty amongst households. In addition, an underdeveloped financial system with a low level of competition creates an ineffective financial system and discourages improvements in the level of financial inclusion in an economy. Our finding is supported by a recent study that found household consumption improved countries that had a financial inclusion index score of 0.356 or higher. For the relationship between financial inclusion and Human Development Index (HDI), which is the proxy for income inequality in this study, I find that financial inclusion positively and significantly influences HDI in Ghana. A possible explanation could be that financial inclusion enables households and individuals to afford education to build their skill and capacity, which can help them to secure employment with better and sustainable disposable income to reduce the overall level of income inequality in the country. Access to finance (through borrowing from the financial sector) can support the financial needs of individuals and households as well as help those individuals with entrepreneurial ambition to start small businesses, which can generate further income for them. Further, access to the financial sector helps individuals to save and invest their excess disposable income to generate investment income. Therefore, financial inclusion helps to reduce the level of income inequality amongst households in Ghana. I also find that the GDP per capita growth, ICT literacy and personal inward remittances have positive, significant effects on the HDI level in Ghana, whereas government spending and rural population growth have an inverse effect on HDI. Inflation (negative) and trade openness (negative) both have an insignificant impact on HDI in Ghana over the study period. I also find that FII*GNI per capita is positive and significantly impacts the HDI. An index to measure the level of women’s empowerment in Ghana is missing from the Ghanaian empirical literature. This study uses the PCA approach to create a women empowerment index for Ghana using four dimensions (labour and economics; good-life and health; politics, governance and leadership; and education and skill building) to find that the level of women’s empowerment improved year-on-year during the study period (1990 – 2021). Despite the fact that many studies have suggested that financial inclusion improves women’s empowerment (and vice versa), a study examining the direction of the relationship is missing from the Ghanaian literature. This study investigates the relationship and finds that financial inclusion and women empowerment are positively related during the study period, which means Ghanaian women are increasingly being empowered as time passes. In investigating the relationship between financial inclusion and women’s empowerment, I find that labour and economics, and politics, governance, and leadership exhibit positive, significant relationships with the level of financial inclusion in Ghana whereas good-life and health, and the education and skill building dimensions exhibit a positive but insignificant relationship with financial inclusion in Ghana over the study period.
Embargo
Model analysis of electrostatic interactions of ATP-IDE interactions by quantum mechanics/molecular mechanics (QM/MM) calculation and molecular dynamic (MD) simulations : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2024) Somin, Sarawoot
The insulin-degrading enzyme (IDE) plays a significant role in the degradation of the amyloid beta (Aβ), a peptide found in regions of the brain of patients with early Alzheimer’s disease (AD). Adenosine triphosphate (ATP) allosterically regulates the Aβ-degrading activity of IDE. Electrostatic interactions between ATP-IDE including thermostabilities/flexibilities of IDE residues, at the allosteric site of IDE, are essential for drug design. These electrostatic interactions and the thermostabilities/flexibilities of IDE residues at the ATP-binding domain have not yet been systematically understood. The present study elucidates the electrostatic interactions of ATP-IDE interactions and the thermostabilities/flexibilities of the IDE residues. Computational modelling based on (QM/MM) calculation method and molecular dynamic (MD) simulations may offer great opportunities to understand biological interactions. In this study, we apply QM/MM to the proposed computational model for exploring the electrostatic interactions of ATP and IDE. Molecular dynamic (MD) simulations are performed at different heat-shock temperatures for identifying thermostable and flexible residues of IDE at ATP-binding domain. The proposed computational model contains five main procedures, including initial structure preparation, molecular docking, molecular mechanics (MM) equilibration, QM/MM minimisation and MD simulation. Since the allosteric effects resulting from the interactions of Aβ peptide can influence the conformational change at ATP-binding domain, we create two systems for comparing the difference between system with and without the interaction of Aβ peptide. Subsequently, the binding affinity of the electrostatic interactions of ATP-IDE interactions can be identified after performing QM/MM minimisations. Furthermore, we perform the MD simulations to explore the thermostabilities/flexibilities of the IDE residues at the different temperatures (300K, 321.15 K and 315.15 K), which 321.15 K and 315.15 K are the temperatures induce a heat-shock response (a protective mechanism) of IDE. The proposed computational model predicts QM/MM minimised structures. Subsequently, it reveals the IDE residues with high binding affinity (LYS530 and ASP385). Considering root-mean-square-fluctuation (RMSF) values during the MD simulations at the heat-shock temperatures, it indicates that LYS530 and ASP385 are also the thermostable residues of IDE, whereas SER576 and LYS858 have high flexibilities with compromised thermostabilities. The present study sheds light on the phenomenon of biological recognition and interactions at the ATP-binding domain within the IDE which has important implications for pharmacological drug design. The proposed computational model may facilitate the development of allosteric IDE activators/inhibitors which mimic ATP interactions.
Embargo
Novel drivers of voluntary intake of low dry matter forages in sheep : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2023) Jayasinghe, Nadeesha Kumari
Fresh forages account for a significant part of the ruminant’s diet in pasture-based systems. Previous studies have suggested dry matter content below 16% reduce dry matter intake, but contemporary NZ temperate grazing systems using a range of low DM% forages are reported to have strongly positive production features, so, an experimental series (1, 2 and 3) was designed to assess DMI using fodder beet (FB), plantain, chicory and ryegrass cultivars using young sheep. In experiment one, DMI, water intake, urine volumes and mineral (Na, K, Ca, Mg, P) balance were measured with young sheep using metabolism crates and fresh harvested FB to represent a total diet DM% below 14%, with grass silage (GS) as a control. Eight (49±1.75 kg) Coopworth hogget rams were fed one of the three treatments, sequentially in runs 1 to 3; treatment 1 (ad libitum GS) - FB 0%: GS 100%; treatment 2 (restricted FB) - FB 30%: GS 70%; treatment 3 (ad libitum FB) - FB 90%: GS 10%. Total diet DM% were 43.21, 30.44, and 13.56%; total diet CP% were 13.38, 13.97, and 12.18%; and total diet NDF was 57.19, 43.13, and 22.29%, respectively for runs 1, 2 and 3. In run 3 the mean daily DMI was greater at 2.74% of LWT compared to run 2 (2.21%) and run 1 (2.49%) (p<0.05). Mean daily water intake in run 3 was 239 ml/kg of LWT, fourfold higher (p<0.05) than observed in run 1 (61 ml/kg of LWT). Mean daily urine production in run 3 was 160 ml/kg LWT, significantly greater (p<0.05) than observed in run 1 or run 2. The mean daily Na intake in run 3 was 21.27 (g/d), significantly greater than runs 1 and 2 (p<0.05), with greater (p<0.05) urinary Na concentration and mean daily urinary Na output in run 3, increasing from 105 to 2090 (mg/L) and 0.14 to 17.89 (g/d) runs 1 to 3. Mean daily N intake was not different between runs, while mean daily urinary N output (g/d) was significantly lower in run 3 (6.19g/d) compared to run 1 (7.88 g/d). Urinary N% was greater in run 1 than run 2, and run 3 (0.6, 0.28 and 0.08% respectively). The N utilization (N retained/total diet N) was greater in run 3 (67%) compared with run 1 (35%) and run 2 (33%). The DMI observed in run 3 was high by comparison with other pen fed harvested forage studies, but lower than the intake observed in grazed forages of similar DM%, and neither the NDF intake nor the CP content of the diet likely limited intake. There was no evidence of rumen dysfunction, and it was concluded that, when FB was fed ad libitum, despite being a low DM% forage, high DMI could be achieved, and the very high urine volumes observed suggested a role for Na in excreting the considerable water load consumed with these DMI. However, it was not clear whether all these effects could be related to an effect of increased Na intake in ad libitum FB diet. Plantain and chicory are low DM% forages that have higher Na content compared to ryegrass, and comparatively high N content compared to FB. Therefore, the second experiment was conducted to investigate the role of Na in DMI in low DM% forages, using eight different plantain varieties, chicory, and ryegrass, in four different sequential runs. In each run, 32 young sheep (41±7kg) were used in four groups of eight animals, with the first two runs using the same sheep and forages on a 14d delay and were conducted as sequential runs. In runs 1 and 2 the treatments were tonic, agritonic, ecotain (plantain varieties) and ryegrass, and in run 3 the treatments were tonic, captain, SF and oracle (plantain varieties), and in run 4 the treatments were tonic, tuatara, boston (plantain varieties) and chicory. In all four runs, ad libitum feed was given (refusals > 20%). Despite low DM% (8.47 to 16.56%), plantain and chicory treatments recorded significantly higher (p<0.05) DMI compared to the grass treatments where DM% varied from 13.06 to 16.17%. The DMI/fasted LWT varied from 3.1 to 5.0, 3.5 and 2.6 to 3.2% respectively for plantain, chicory and grass, and the mean daily NDF intake for plantain and chicory varied from 0.74 to 1.64% (NDF/LWT), and for grass 1.17 to 1.22%. The mean daily urine production was highest in the chicory treatment (11654 ml/d), and expressed against fasted LWT, 177 to 294 ml/kg for the plantain and 98 to 118 ml/kg for the grass treatment. Mean daily Na intake in plantain varied (0.3 to 10.57 g/d) across runs, but all except boston and tuatara treatments were >3g/d, while the chicory treatment was 3.5g/d, and both mean plantain and chicory values were significantly greater (p<0.05) than the mean of the grass treatments (0.43 g/d). The plantain treatments in runs 1 and 2 had greater (p<0.05) mean daily urinary Na concentration and mean daily urinary Na outputs (g/d) compared to the grass treatments. The mean daily Na intake (3.51 g/d) was lower in the chicory treatment, and the mean daily urinary Na output for chicory treatment (3.51 g/d) was equal to the intake. Despite the plantain DM% doubling from run 1 to run 2, the mean daily total water intakes were closely similar between runs within plantain treatments (range 378-398 vs 366-376 ml/fasted LWT, respectively for run 1 and run 2). When the mean daily DMI was expressed against LWT, run 2 plantain treatments were observed to have the highest for any treatment (4.62 to 5.08% of LWT) in all four runs, and it was concluded this water intake was an effective upper physiological limit, thereby limiting DMI. The results from this experiment do not support the hypothesis that forage DM% below 16% restrict DMI, and it was concluded that a total water intake of approximately 370-400ml/ kg LWT represents a physiological upper water intake limit, and that a daily urinary Na concentration of approximately 300mg/L, and a daily urinary Na output of approximately 3.5g was required to enable corresponding urine outputs to achieve the DMI observed. It was also concluded that diet Na content and daily intakes facilitated water excretion, and that only sufficient Na intakes would therefore enable high DMI with low DM% forages. The third experiment was conducted to investigate the effect of Na on DMI and urine production when the animals were externally dosed with Na while feeding on low DM% pasture that was originally low in Na. Twenty-four young sheep (39±5 kg) were divided into three groups of eight and three dietary treatments were used in two sequential runs in a cross-over design (grass and grass + salt treatments). The ad libitum FB treatment was maintained as the control treatment in both runs, while the other dietary treatments were grass and grass + salt (12 g of Na was added via oral drenching to achieve a daily intake similar to that of ad libitum FB feeding treatment). The mean daily DMI and the mean daily DMI/fasted LWT were significantly lower (p<0.05) in the FB treatment in both runs 1 and 2, and no significant differences (p<0.05) were observed between the grass treatment or grass + salt treatments in DMI or DMI expressed against LWT. The mean daily NDF intake expressed against the LWT was significantly higher (p<0.05) in the grass treatment and grass + salt treatments compared to the FB treatment and varied from 1.14 to 1.22% from run 1 to run 2. The mean daily urine production (ml/d) was not significantly different (p<0.05) between treatments in run 2, but in run 1 the grass + salt treatment was greater than the FB treatment. The mean daily total water intake expressed against fasted LWT were significantly higher (p<0.05) in grass and grass + salt treatments than the FB treatment, while in run 2, none of the treatments were found to be significantly different. The mean daily feed Na intake (g/d) was significantly higher (p<0.05) in the grass + salt treatment than in grass treatment in both runs. Despite the five to tenfold greater mean daily Na intake in the grass + salt compared to the grass treatment, there were no significant differences in mean daily urine production among the grass and grass + salt treatments in run 1 or 2. The urinary Na concentration was significantly increased (p<0.05) in the grass + salt treatment compared with the grass treatment (1316 vs 223 mg/L). The mean daily urinary Na mass output (g/d) was significantly higher (p<0.05) in the grass + salt treatment in both runs compared to the grass treatment. In both run 1 and run 2, grass + salt treatment had significantly higher (p<0.05) urine production (ml) and urinary Na output (g) in the early part of the diurnal period compared to that with the latter part. However, both grass and the FB treatments did not significantly differ in urine production (ml) and urinary Na output (g/d) during the diurnal period. It was concluded that supplemented Na does not necessarily increase the DMI or the urine volume in the grass + salt treatment despite the grass treatment being low in DM% (<16%), when the DMI was likely to be initially restricted by the NDF intake (1.14 to 1.22% NDF/LWT), and the excess of Na intake could have led to increase the urinary Na concentration once the minimum Na intake has been reached without necessarily increasing the urine production. It was concluded the lower DMI observed in the FB treatment was most likely a result of the CP content of the FB diet (8.06-8.38%) limiting the RDP of the diet. From the results of this series of experiments it was concluded that when FB was fed ad libitum, despite being a low DM% forage (<16%), high DMI could be achieved, and therefore high urine volumes were associated with this intake. It was also concluded that low DM% in forages did not restrict DMI if the animals consumed sufficient daily Na intake to enable high urine outputs of a minimum Na concentration (c.300mg/L) required for diuresis, and if the animals remained below a physiological upper water intake limit of approximately 370-400ml/ kg LWT, which was observed with the DMI observed in very low DM% forages such as some plantain and chicory treatments in this study. This process required a daily Na output of approximately 3.5g to enable corresponding urine outputs allowing the DMI to be increased in low DM%. However, supplementary Na does not necessarily increase the DMI or the urine volume despite the forage being low in DM% (<16%) if the DMI is restricted by the NDF intake, suggesting Na supplementation on most NZ ryegrass pastures will not be effective. In such cases, the excess of Na intake leads to an increase in urinary Na concentration once the minimum Na intake has been reached without necessarily increasing the urine production or the DMI.
Open Access
Nutrifermentics: Microbial epigenetics for innovation in fermentation : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2023) Kong, Yanzhuo
Microbial epigenetics presents a novel and efficient approach for manipulating microorganisms without altering their genetic information. This present study focuses on harnessing the potential of microbial epigenetics to transform and revolutionise fermented product development, a concept termed "nutrifermentics." The dynamic interplay between microbial epigenetics and dietary factors were investigated in both eukaryotic (Saccharomyces cerevisiae) and prokaryotic (Lactobacillus acidophilus) strains, with a specific focus on the capacity of nutrifermentics to drive innovations in fermentation, particularly within the food industry. In this study, benzoic acid, a common food additive and a recognised histone deacetylase inhibitor (HDACi), was shown to alter the formation of epigenetic histone marks (H3K4Me2, H3K27Me2, H3K18ac, and H3Ser10p) in S. cerevisiae yeast. Consequently, the phenotypic behaviour of the yeast was altered, with increased production of phenylethyl alcohol and ester compounds during alcoholic fermentation observed. Subsequently, the relationship between short-term and long-term stress induced by benzoic acid in yeast and their effects on aging was explored. Through comprehensive transcriptomic and metabolomic analyses, it was established that short-term stress fosters longevity, while long-term stress diminishes lifespan. Interestingly, cells under long-term stress (LT) demonstrate the activation of genes associated with epigenetic regulatory enzymes and secondary stress response genes, including heat shock proteins (HSPs). Paradoxically, despite this heightened cellular stress response activity, these cells exhibit shorter lifespans when compared to their short-term stressed counterparts (ST). These findings indicate there is a potential evolutionary advantage, specifically an enhanced short-term survival, associated with aging markers like HSPs. Additionally, these results imply potential applications for aging interventions through the use of inhibitors targeting heat shock proteins. To determine the impact of a diverse range of epigenetically active compounds, such as genistein, in bacteria, the epigenetic responses of L. acidophilus, a well-known probiotic bacterium widely used in yoghurt production, were evaluated. Epigenetics, transcriptomics, and metabolomics were used to demonstrate the potential to alter individual gene or loci expression without genetic modification. The production of both primary and secondary metabolites, such as melibiose, were altered in response to different epigentically active compounds, which provides insight into the role these dietary compounds can play in enhancing bacterial fermentative capability in a sustainable and genetic modification-free way. In conclusion, this present study unveils the potential of microbial epigenetics and dietary compounds to enhance fermentation processes. It offers valuable insights and practical applications for researchers and industries in the field of fermented product development and biotechnology applications.
Embargo
The dynamics of socially responsible investment funds’ performance persistence : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2024) Shanthirathna, Neleesha
Socially Responsible Investment (SRI) is an investment strategy that considers social, ethical and environmental elements in investment. SRIs have grown into a widely followed investment practice offering a variety of products to investors. This fund industry is more focused on embracing sustainability practices in its operations. Performance persistence is a good indication for investors, analysts, portfolio managers and institutions. However, there is a paucity of research on the persistence of SRI funds. This study analyses the performance persistence of SRI funds in the United States (US) from 2001 to 2021, including the 2008 global financial crisis and the COVID-19 pandemic crisis. First, we examine the performance persistence of SRI funds before, during and after the 2008 global financial crisis. Second, we investigate the performance persistence of SRI funds before and during the COVID-19 pandemic crisis. Third, we focus on the relationships between fund-specific factors and the performance persistence of SRI funds. Finally, we explore the impact of macroeconomic indicators on the performance persistence of SRI funds. We use Carhart (1997) and Fama French (2015) models to measure the performance of SRI funds. We then follow Hendricks, Patel and Zeckhauser (1993) and Carhart (1997) recursive methods to analyse the performance persistence of SRI funds. We use multinomial logit regression to identify the relationships between fund-specific factors (fund size, age, flow and asset class), macroeconomic variables (interest rate, inflation, money supply and economic activity) and the performance persistence of SRI funds. Our results reveal a positive, significant performance persistence in SRI funds before and during the 2008 global financial crisis. However, the results show no evidence of performance persistence before the COVID-19 period crisis; only the nonparametric tests reveal positive performance persistence of SRI funds during the COVID-19 pandemic crisis. Fund characteristics and macroeconomic variables significantly affect the performance persistence of SRI funds. We divide the study period following the 2008 global financial crisis and the COVID-19 pandemic crisis. Our results show most fund characteristics and macroeconomic variables are significant after the 2008 global financial crisis and before the COVID-19 pandemic crisis. This is the first empirical study to evaluate these aspects of the performance persistence of SRI funds. Identifying SRI fund performance persistence in different market conditions is important for investors to make better investment decisions, manage risk and build a diversified portfolio. Fund analysts can identify potential problems early and adjust their recommendations. They can enhance their reputation as trusted advisors by providing informed recommendations.
Open Access
Conflicted property rights – balancing the need for seismic safety with heritage conservation : A thesis submitted in partial fulﬁlment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2023) Nahkies, Peter Brent
Traditionally described as a “bundle of rights” the creation and protection of private property rights is seen as a cornerstone of western democratic societies. However, property rights are not fixed but are a constantly evolving mix of private rights and community rights that ebb and flow with changing community expectations. As a result of the Christchurch earthquakes increased community expectations of seismic safety led to the passing of new legislation imposing mandatory seismic mitigation for buildings considered an unacceptable risk to society. These buildings are defined legally as “earthquake-prone”. The costs of seismic mitigation must be met by the property owner potentially causing significant financial hardship to the individual, but also with the potential to have significant negative impacts on communities. One form of mitigation promoted by the legislation is to demolish the building which puts the owner of an earthquake-prone building with heritage value in conflict with community expectations of heritage conservation. This conflict often leads to litigation with an owner demanding the right to demolish while the community pursues the retention of the heritage building. The results of the litigation are uncertain and often costly. This thesis looks at altering property rights in New Zealand in order to avoid litigation and achieve a more equitable balance between private and public rights and thus achieve a better balance between safety, heritage and property rights. This rebalancing is necessary to protect individuals from financial hardship. It is also necessary to achieve better outcomes for communities by protecting them from the unexpected outcomes of the new legislation and by promoting sustainability by reducing building demolition and instead facilitating heritage-led urban regeneration.
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Assessing the prevalence, diversity, and damage potential of plant-parasitic nematodes on maize (Zea mays L.) : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2024) Nagarathnam, Thiruchchelvan
Maize cultivation faces challenges from plant-parasitic nematodes (PPNs), which can significantly reduce yields. Despite their importance, PPNs are often underestimated in agricultural ecosystems. Research in New Zealand and Sri Lanka reported the presence of PPNs in maize fields. However, comprehensive data is still lacking. Environmental factors such as soil pH, moisture content, nutrient levels, and rainfall could influence PPN population densities and pathogenicity. Hence, understanding PPN dynamics and environmental interactions is crucial for sustainable production. This study aimed to; i) examine the prevalence, abundance, and distribution of PPNs associated with maize cultivation in Sri Lanka and New Zealand, ii) identify the most abundant PPN species and their distribution in New Zealand maize fields, iii) investigate the relationship between soil edaphic and climatic characteristics with PPN abundance in New Zealand maize fields, and iv) screen the susceptibility of commercially available maize hybrids in New Zealand against the most abundant PPN genus under glasshouse conditions. A survey conducted in Sri Lanka's semi-arid regions with major maize cultivation areas found that over 92% of maize fields tested positive for PPNs. The dominant species was Pratylenchus spp., with a mean population density of 2020 kg-1 of soil. Sampling at different maize growth stages revealed that Pratylenchus spp. populations were below 1000 kg-1 of soil at the seedling stage but increased by 2 to 10-fold at harvest. In New Zealand, a total of 384 soil samples were collected from 25 sites from both the North (NI) and South Island (SI) of New Zealand from maize growing regions. The major PPNs identified by morphology were Pratylenchus (91%), Helicotylenchus (38%), Meloidogyne (14%), Tylenchus (14%), Heterodera (8%), Paratylenchus (3%), and Criconemella (1%). Pratylenchus spp. were widespread across all surveyed regions. In most sampled sites from both islands, Pratylenchus spp. exceeded 1000 kg-1 of soil, which is recognised as the economic threshold set by nematologists worldwide. Five Pratylenchus spp. in New Zealand maize fields: P. crenatus, P. neglectus, P. thornei, P. penetrans, and P. pratensis, were identified based on morphology and the sequencing of DNA-PCR products extracted from single nematode using Sanger sequencing. Among these, P. crenatus and P. neglectus were predominant across maize-growing regions in New Zealand. The soil analysis revealed that tested soil properties varied between the sampled regions, while PPN abundance and diversity exhibited a regional dissimilarity. The relationship between PPN composition and soil physicochemical properties of New Zealand maize fields analysed using the canonical correspondence analysis (CCA). Results showed that soil moisture, pH, soil P, and percentages of sand, clay, N, and C significantly influenced PPN abundance and distribution. However, the influence of soil parameters on the PPN population varied within the regions, where soil moisture content was the main driver for the PPN population abundance within all three regions. A year-round sampling conducted at one of the sites in the Canterbury region of SI revealed the influence of seasonal and cropping factors on PPN abundance. This indicated a 5-fold population increase of Pratylenchus spp. from crop establishment to maturity during a season. Also, CCA on seasonal variations on soil physicochemical, climatic factors, and PPN population abundance in a field revealed that the soil moisture, volumetric water content, bulk density, sand%, N and C with the climatic factors; rainfall, relative humidity, and sunshine hours had a significant relationship with PPN population dynamics. Three nematode extraction methods for maize roots were tested. Centrifugal sugar flotation yielded the highest nematode count but with low clarity for microscopic observation. The Baermann funnel had 35.9% extraction efficiency with high clarity. The Whitehead tray had 60.8% efficiency with moderate clarity compared to centrifugal sugar flotation. The Whitehead tray is a good compromise for clarity and count, while sugar flotation is efficient and faster processing of samples for Pratylenchus nematodes, adding another layer of information for future studies. The outcomes from the glasshouse experiments using 15 commercial maize hybrids and a mixed field population of Pratylenchus spp. showed that most tested maize hybrids were susceptible to Pratylenchus spp. and demonstrated varying degrees of susceptibility. Another glasshouse experiment was conducted to determine the pathogenicity and reproduction of Pratylenchus on three selected maize hybrids based on the results from the previous trials. The results demonstrated significant reductions in root dry weight across hybrids, with losses ranging from 33% to 42%, and shoot weight losses varied among hybrids 10 to 22% compared to the controls 60 days after planting. This is the first comprehensive study on the PPN community association with maize in Sri Lanka and New Zealand. These findings emphasised the potential impact of PPNs, particularly Pratylenchus spp., on maize yield in both countries, highlighting the urgent need for further research to develop effective PPN management tactics adapted to local conditions.
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Factors influencing GlobalGAP adoption and its impact on income and production costs of small-scale pineapple farmers in Ghana : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2023) Annor, Prince Baah
The adoption of Global Good Agricultural Practices (GlobalGAP) improves food quality and safety along fresh produce value chains, but adoption rates have been low among small-scale pineapple farmers in Ghana. Low adoption rates have contributed to a fall in smallholder participation in export-oriented production and declining export performance. While policymakers and other industry stakeholders have tried to find ways to improve GlobalGAP adoption in Ghana, little is known about the determinants and impacts. Consequently, stakeholders do not know which smallholders are most likely to respond positively to interventions aimed at promoting adoption. Moreover, previous studies have identified significant increases in smallholder production costs associated with GlobalGAP compliance. However, there is limited information on how specific inputs used by GlobalGAP certified farmers increase production costs. Such information would help policymakers to target interventions at the most important drivers of quality-enhancing compliance costs. Furthermore, it would make adoption more affordable to farmers and less expensive for taxpayers who fund these interventions. In the first instance, this study set out to measure the impact of GlobalGAP adoption on the net incomes of smaller and larger small-scale pineapple farmers, recognising that compliance incurs significant fixed costs, and that fixed costs pose a greater obstacle to adoption on smaller farms. Small-scale farmers were defined as those operating farms no larger than five hectares. The study used probit and two-stage regression models to estimate the impact of GlobalGAP adoption on net income. These techniques were applied to a representative sample of 546 small-scale pineapple farmers located in Ghana’s two leading export production districts. Of these 546 farmers, 236 were GlobalGAP adopters; the remaining 310 were non-adopters. The probit model showed that the probability of adoption was higher for households that had larger land endowments, were members of an agricultural cooperative, engaged with extension services, and had female heads. The regression models showed that GlobalGAP adoption reduced net income on farms producing less than one hectare of pineapples, but increased net income on farms growing more than one hectare of pineapples. The study thus recommends that extension and other interventions intended to promote GlobalGAP adoption amongst pineapple farmers in Ghana should be targeted at those able and willing to grow more than one hectare of pineapples. Second, this study used a quality-adjusted transcendental logarithmic (translog) cost function to identify the main contributors to production costs in the sub-sample of 236 GlobalGAP adopters. The results showed that production cost is most sensitive to changes in the plantlet price, followed by wages, agrochemical prices, and expenditure on capital items. Smaller small-scale farmers are much more sensitive to increases in capital expenditure than are larger small-scale farmers. Post-estimation analysis showed that improvements in product quality increased production costs at an increasing rate. Key policy recommendations include joint ventures to increase nursery capacity and competition in the market for plantlets, scrutiny of mandatory fees impacting the cost of imported labour-saving inputs, facilitating sharing arrangements between smallholders to lower the cost of on-farm infrastructure, and research to identify constraints preventing certified farmers from exploiting size economies.
Open Access
Spatial agroecology: modelling multiple ecosystem services in periurban landscapes : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2024) Morris, Richard Minton
Urban growth and agricultural intensification share a common trait of reducing landscapes' capacity of producing the critical ecosystem services (ES) on which they depend. The objective of the work described in this thesis was to develop a spatially explicit ES-based design method for the configuration of landscapes to generate regulating ES. Literature review, which is described in Chapter 2, identified a nexus of four research fields - Ecological Urbanism, Landscape Ecology, ES science and agroecology - as an unexplored framework for this ES-based design approach. The method used in this work is described in Chapter 3, where a key flaw in current ES modelling tools forms the basis for a Geographic Information Systems (GIS)-based conceptual model, ESMAX. Present models are characterised by 'the biophysical gap', an oversight of spatial interactions between ES-supplying landscape components. This inhibits their application to spatial design i.e., the configuration of those components to enhance ES performance. ESMAX is structured around the fundamental natural phenomena of distance-decay as exhibited by all regulating ES, enabling an original method of quantifying and visualising regulating ES produced by different configurations of landscape components. The results of Chapter 3 conceptually validated the model and provided the data for Chapter 4, which proposed a model for assessing landscape multifunctionality (or simultaneous supply of multiple ES) from different landscape configurations. Importantly, the results for different configuration options generate a solution space with which to negotiate specific ES demands and specific contextual spatial constraints. Chapter 5 applied ESMAX and the solution space in an agricultural context. This spatial agroecological approach determined that different configurations of the same total area of trees in a 1 ha paddock produce markedly different levels of ES performance, and that this approach may be useful in supporting an adaptive transition from conventional agriculture to agroecologically based farming systems. Chapter 6 applied spatial agroecology to a 190 ha periurban development site, demonstrating how the same apportioned area of agroecological systems, when subdivided and distributed differently across the site, has a significant bearing on multiple ES production. This suggests that urgent consideration should be given not only to placing trees on farm, but how trees should be placed on farm. Similarly, it supports not only the integration of agriculture with urban systems, but the specific spatial design of agroecological systems to address the regulating ES demands of the urban system. The spatial agricultural approach outlined in this thesis highlights the potential for agroecology in the Anthropocene as a spatially effective source of multiple regulating ES to surrounding communities at various scales.
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Integrative dynamics of action potential in Axon Initial Segment (AIS) of neurons: A novel computational model : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2023) Pashang, Abolghasem
The Axon Initial Segment (AIS) plays a critical role in neuronal excitability and action potential initiation. Computational modelling of the AIS can provide valuable insights into the biophysical mechanisms underlying these processes and their relevance to various AIS-related disorders. The Hodgkin-Huxley model laid the foundation for understanding action potential initiation, utilising empirical differential equations to describe sodium and potassium ion conductance and their gating functions. However, the specific role of the scaffold protein Ankrin-G (AnkG) in regulating ion channel function and ion currents in the AIS remains poorly understood. This thesis investigates the impact of AnkG concentration on sodium (Nav) and potassium (Kv) channel gating and ion current properties using electrophysiology, molecular biology, and computational modelling approaches. AnkG acts as a molecular bridge between the Nav and Kv channels and the cytoskeleton, ensuring proper channel localisation and density in the AIS. Disruptions to AnkG expression can lead to alterations in channel localisation and function, affecting neuronal excitability and firing properties. This thesis endeavors to unravel the mechanisms underlying AnkG's influence on Nav and Kv channel function and its subsequent impact on ion currents in the AIS. Understanding these interactions is crucial for comprehending the pathogenesis of AIS-related disorders and shed light on the complexities of action potential initiation and propagation in neurons.
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Can the presence of a fungal volatile organic compound improve plant resilience to abiotic stress? : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2023) Echaide Aquino, Jesus Francisco
Climate change is a matter of increasing concern, as the severity, duration, and area affected by drought have steadily risen since the 1970s. These changes have severely affected the agricultural industry, as drought stress is a major contributor to crop loss. Therefore, it is crucial to develop new strategies to address this problem. Seed coating shows the potential to mitigate the challenges faced by the agricultural industry, as it provides physical and physiological properties to seeds, helping alleviate both biotic and abiotic stress. This research aims to evaluate the protective effect of the fungal volatile (FVOC) organic compound when applied via polymer seed coating. The FVOC seed coating treatment's effects were assessed regarding plant emergence, resilience to drought stress, and transgenerational stress adaptations. By conducting a comprehensive transcriptomic analysis, it was possible to identify the transcriptional changes induced by the presence of the FVOC molecule. The application of the FVOC led to significant changes in gene expression in plants under drought-stress conditions, enabling them to cope more effectively with stress. Moreover, when plants grown from FVOC-treated seeds were exposed to a second round of drought stress, they exhibited a more specific and refined response to this stress. Moreover, when the second-generation plants derived from FVOC-treated seeds were exposed to drought, they exhibited improved resilience to environmental stress. This observation strongly suggests the occurrence of transgenerational changes. The drought stress initially triggered these changes in the first-generation plants and was further enhanced by the presence of the FVOC molecule. Subsequently, these changes were transmitted to the second generation, resulting in enhanced resilience plants.
Open Access
An investigation of systematic camera trap monitoring for kiwi (Apteryx spp.) : A thesis submitted in partial fulfillment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2023) Tansell, A Jane S
Introduction: Kiwi (Apteryx spp.) are one of New Zealand’s national taonga/taoka (treasures) that are our responsibility and privilege to protect. To inform protective management, we need to monitor kiwi population responses to management, for which a non-invasive method that can detect all age classes has been lacking. Camera traps are non-invasive monitoring devices, which are increasingly used with recently developed analyses to monitor cryptic terrestrial species around the world. To apply these methods to kiwi, standardized methods need to be developed and benchmarked against existing methods. Aims: The aims of this study were to 1) summarise previous monitoring work on kiwi to develop a draft systematic camera trap monitoring method for kiwi, 2) determine optimal site selection and camera trap set-up, 3) determine optimal survey length and camera trap spacing for use with spatial presence-absence (SPA) analysis and identify whether realistic population estimates are obtained, 4) compare camera traps with a current noninvasive method using acoustic recorders to determine if they give realistic and comparable estimates when used with SPA, 5) compare camera traps with dog survey and an observer listening survey to assess kiwi population health, 6) trial alternative analyses for use with camera traps in high density sites, 7) investigate stereo cameras for their potential to add value to camera trap surveys. Materials and methods: We summarised the current literature on monitoring kiwi and the use of camera trap surveys. We deployed 34 camera traps over six seasons in Orokonui Ecosanctuary. We deployed 29 acoustic recorders and carried out detector dog surveys to compare the number of juveniles detected. We deployed 17 camera traps in Rotokare Scenic Reserve and 18 camera traps in the Cape Sanctuary to examine their effectiveness in high kiwi density areas. We constructed a stereo camera by chaining two off-the-shelf trail cameras together to trigger from one PIR sensor and briefly trialled the stereo camera at Orokonui. Results: Cameras were able to detect kiwi of all age groups and to provide credible population densities and trends. Kiwi detections can be maximised by using a detector dog team to select camera sites and through camera orientation. Comparable population estimates were obtained using spatial presence-absence (SPA) analysis with an optimal survey length of four months, during peak incubation, and optimal camera spacing of 350 m. Cameras and acoustic recorders gave comparable population estimates using SPA. Estimates were realistic based on matrix population model projection. Camera traps and detector dog surveys found a similar number of juvenile kiwi. Estimates obtained using Royle-Nichols analysis likely underestimated population size but correctly indicated population trend direction and magnitude, while the index-manipuation-index method did not give a biologically possible estimate of population density. The stereo camera method using two trail cameras was capable of giving surprisingly accurate bill measurements, but further work in necessary to achieve repeatability. Discussion and conclusions: Systematic camera trapping is capable of monitoring the whole kiwi population, including female and young kiwi that are usually under-recorded by other methods. Systematic camera trapping paired with spatial presence-absence analysis performed well in a low density population. Camera monitoring shows much promise as another useful noninvasive tool in the kiwi monitoring toolbox.
Open Access
Ryegrass endophyte mixtures for improved animal health : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2024) Milsom, Andrew
In New Zealand, perennial ryegrass (Lolium perenne) with endophyte (Epichloë festucae var. lolii) is a standard ingredient of pastures where insect pests challenge the persistence of the ryegrass. Farmers currently have multiple ryegrass cultivar x endophyte strain combinations from which to choose the best match for their requirements. However, no single cultivar x strain combination provides both the highest insect protection and lowest occurrence of ryegrass staggers and heat stress in animals grazing pasture with endophyte. Furthermore, the current industry protocol for testing the safety of animals grazing a grass x endophyte combination involves exposing the animals to a simulated worst- case scenario and needs reassessment. This research aimed to examine the effects of endophyte diversity in perennial ryegrass on the health and performance of sheep using a modelling approach so that an animal response of any mixture could be predicted as a function of the mixture’s endophyte proportions, thus minimising the need for animal testing in the future. At Barenbrug Plant Breeding Station, Courtenay, Canterbury, eight pasture treatments of Maxsyn perennial ryegrass – seven that varied widely in sown proportions of three endophyte strains – nea3, nea12, and standard endophyte (SE) – and an endophyte-free control (nil), were tested over four experimental runs from February 2020 to December 2021. There were three monocultures (100% of each strain), three binary mixtures (50% of each of two strains) and one ternary mixture (33.3% of each strain) of endophyte based on a simplex centroid design. The eight treatments were randomised in three blocks of 0.156-ha plots. The animal responses of interest were ryegrass staggers, liveweight gain, heat stress, and diet selection of grazing sheep. The first experiment run was a test for ryegrass staggers in February 2020. Endophyte toxicity in late summer is typically near its annual maximum in Canterbury, so the timing of this run created a ‘worst-case scenario’ for ryegrass staggers. The pastures were managed in the previous spring so as to accumulate a large herbage dry matter (DM) mass (about 3700 kg DM/ha above a cutting height of 40–50 mm) of low nutritive quality feed (metabolisable energy (ME) = 8.7 MJ/kg DM and crude protein (CP) = 4.9%). The pasture available (kg DM/ha) was high enough for lambs to remain in the same plots for a 4-week testing period at a stocking rate of 64.1 lambs/ha. Ryegrass staggers was severe (score 4–5) in the lambs grazing the SE pasture after 8 days and in all other endophyte monocultures and mixtures after 22 days. Mixture models fitted to the staggers response data predicted the staggers score for any combination of sown endophyte proportions and identified an optimum of 65% nea3 and 35% nea12 which delayed severe staggers by 1 week. Ryegrass staggers was associated with tremorgenic alkaloids in the herbage above 40–50 mm: epoxy-janthitrem I of nea12 (1 ppm), paxilline and terpendole C of nea3 (0.1 and 1.2 ppm), and lolitrem B, paxilline and terpendole C of SE (2.2, 0.2, and 1.1 ppm). The second experimental run was a study of liveweight gain and ryegrass staggers under low toxicity conditions from September to December 2020. The spring pastures provided optimal conditions for liveweight gain and the stocking rate was kept consistent at 44.9 hoggets/ha. Pre-grazing pasture mass was ca. 1600 kg DM/ha, ME was 12 MJ/kg DM and CP was 20% above 40–50 mm. The average daily gain for all mixtures was 271 g/day over the first 4 weeks, and 20 g/day for weeks 4–8. The mixture models fitted to the liveweight gain data identified the optimum endophyte formulation that maximised liveweight gain to be a monoculture of nea12 so that the responses were equal to the monoculture performance in the first and second 4 weeks of grazing (292 and 25 g/day). Ergovaline, the alkaloid linked to suppressed liveweight, was present in nea3 and SE pastures at 0.32 and 0.16 ppm. Staggers scoring at the onset of symptoms after 10 weeks of grazing revealed mild staggers (score <2) in SE that persisted until the experiment ended at 12 weeks. The model analysis showed that any mixture containing at least 60% nea3 and up to 40% nea12 and/or SE would result in no staggers (score 0). Alkaloids associated with staggers were in lower concentrations compared to the summer test: 0.8 ppm of epoxy-janthitrem I was present in nea12 pastures while lolitrem B, paxilline, and Terpendole C were present in SE pastures at 1, 0.1, and 0.3 ppm. The third experimental run tested the assumption that endophyte strain proportions in the diet were equal to the sown proportions. Plot fences within replicates were removed, 51–56 hoggets were allocated to each replicate (40.9–44.9 hoggets/ha), and sward height decrease was measured 15 times between 15 February and 16 March 2021. Herbage mass, ME, and CP values at the beginning of grazing were circa 1400 kg DM/ha, 11.5 MJ/kg DM, and 11%. Analysis of variance showed no differences (P>0.05) in sward height decrease between sown treatments, including nil, over the whole grazing period. Mixture models of each measurement date and the average of all dates only showed differences (P<0.05) between linear terms (monocultures) on day 2 and further analysis confirmed the sward height decrease of SE was greater than nea12 (P<0.05), but not nea3. Quadratic terms (binary mixtures) were not different on any date. The mixture model analysis for the whole period predicted that a mixture containing 39% nea3 and 61% SE would maximise sward height decline despite lolitrem B concentrations of SE pastures being sufficient to cause ryegrass staggers (1.4 ppm) and ergovaline levels in nea3 pastures of 0.37 ppm. The lack of deterrence to these alkaloids indicates that animals were unable to differentiate between endophyte strains. The fourth experimental run was a repeat liveweight gain test followed by a heat stress study from October to December 2021. Pasture conditions were similar to the previous liveweight gain test at the start of grazing (ca. 2400 kg DM/ha, 12 MJ ME/kg DM, 15% CP). The same number of hoggets were used as in the previous liveweight gain study, but a higher starting liveweight and greater pre- grazing pasture mass resulted in greater liveweight gain across mixtures in the first and second 4 weeks (397 and 67 g/day) compared to the previous spring. The model analysis predicted an optimum mixture containing 16% nea3, 65% nea12, and 20% SE would result in maximum liveweight gains of 402 and 85 g/day in the first and second 4 weeks of the test. Data loggers attached to controlled internal drug release (CIDR) devices recorded vaginal temperatures in selected mixtures (nea3, nea12, nea3–nea12, and nil) during the final 8 days of the 8-week grazing period. Average temperature for the three mixtures was 39.07°C compared to 38.96°C in the nil endophyte control. Hoggets grazing nea12 had the lowest temperature of the three mixtures (38.94°C; P<0.05). Consequently, the mixture model predicted the optimum mixture would only contain nea12. Ergovaline concentrations were 0.7 and 0.5 ppm in nea3 and SE. An endophyte diversity model that included ryegrass staggers and liveweight gain responses from experimental runs 1, 2, and 4 as multivariates, predicted a mixture containing 77% nea12 and 23% nea3 would give the best overall combination of responses. Although temperature was not included in the model, the vaginal temperature response of this optimal mixture was predicted to be 39.02°C, just 0.06°C higher than the nil endophyte control. This thesis showed that endophyte mixtures can improve the health of grazing sheep and provides the industry with a new option for mitigating health issues associated with endophyte without searching for novel strains. Such mixtures would be best suited to scenarios where insect pest pressure requires the use of endophyte strains that can increase the risk of ryegrass staggers and/or suppressed liveweight gain. The endophyte diversity modelling approach can predict responses to sown strain proportions beyond those included in the experiment, reducing the number of animal entries required for testing.
Open Access
The effects of corporate governance on firm performance in the Association of Southeast Asian Nations (ASEAN): A comparative analysis : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2023) Fernando, Chavika
Increasing dependence on corporate governance (CG) raises questions about whether corporate governance positively impacts firm performance and whether other variables can change the relationship between corporate governance and firm performance. We investigate the relationship between corporate governance features, including board effectiveness, block ownership, and national governance, on the firm performance of ASEAN-6 non-financial listed firms. We use the fundamental features of CG, such as board size, board independence, gender diversity, CEO duality, institution ownership, foreign ownership, insider ownership, government effectiveness, the rule of law and regulatory quality to analyse their impact on firm performance as measured by return on equity and Tobin’s Q. We use 265 ASEAN-6 non-financial listed firms (2385 firm-year observations) from 2010-2019 and uses OLS estimation and System-GMM estimator to control for the endogeneity issue. The results show that, except for CEO duality and insider ownership, that have no significant impact on performance, the other governance mechanisms significantly influence the performance of ASEAN-6 non-financial listed firms. Specifically, board independence, board gender diversity, governance effectiveness, the rule of law, and regulatory quality significantly positively influence ASEAN-6 non-financial listed firms. The results show a significant negative relationship between block ownership variables and the performance of ASEAN-6 non-financial listed firms. From a theoretical perspective, we emphasise how CG impacts firm performance and uncover the importance of CG systems in ASEAN-6 non-financial listed firms. From a practical perspective, we not only explain the optimal structure of CG that can enhance performance but also identify the moderating impact on board effectiveness, block ownership, national governance and the performance of ASEAN-6 non-financial listed firms.
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Exploring the nutritional quality and bioactivity of different rice crackers and the influence of oyster/mussel protein fortification on potential health benefits : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2024) Sui, Limin
In New Zealand, a quarter of the population faces multiple chronic health conditions (Ministry of Health, 2023). Nutrient-dense foods containing essential constituents such as protein, fibre, vitamins, and minerals are pivotal for enhancing immunity, maintaining health, and preventing chronic diseases. Rice crackers, a popular modern convenience snack, are favoured for their ease of preparation, extended shelf-life, and appealing texture (Patil, Brennan, Mason, & Brennan, 2016). However, these crackers primarily utilise refined white rice flour obtained by removing the bran layer from brown rice, leading to low levels of protein, dietary fibre, and bioactive compounds, alongside high levels of rapidly digestible carbohydrates. This nutritional profile raises concerns about their potential high glycaemic index and potential implications for chronic health problems (Lafiandra, Riccardi, & Shewry, 2014). As a result, ongoing research is directed toward innovative reformulations of rice-based products to address these nutrient deficiencies. To comprehensively evaluate the quality of white rice crackers, this study examined and compared rice crackers produced from different rice varieties: white rice, brown rice, and black rice. Brown rice and black rice, being whole grain foods, retain their bran layer and offer higher protein, fibre content, and bioactive compounds such as polyphenols and anthocyanins, associated with reduced risks of hypercholesterolemia, cardiovascular diseases, and type 2 diabetes (Ali, Wani, Wani, & Masoodi, 2016; D. Zhu et al., 2023). The investigation encompassed assessments of physical characteristics, nutritional composition, in vitro starch digestion, and glycaemic response. Results showed that brown and black rice crackers exhibited significantly higher essential nutrient levels, including protein, ash, fat, dietary fibre, and resistant starch, compared to white rice crackers (p < 0.05). In contrast, white rice crackers exhibited a higher glycaemic response, characterised by a higher reduced sugar release and a greater content of rapidly digestible starch, along with a lower content of resistant starch during the in vitro starch digestion process. Regarding quality evaluation, white rice crackers exhibited the highest values for brightness (L* = 73.00) and yellowness (b* = 30.89), while black rice crackers demonstrated the lowest brightness (L* = 25.12) and the highest redness (a* = 6.31). Furthermore, black rice crackers displayed the greatest hardness (1022.46 g), whereas brown rice crackers showcased the highest fracturability (18.27 mm). To future examine phenolic compounds in rice crackers and establish links between in vitro digestion, antioxidative properties, and enzyme inhibition, this study extended its investigation to evaluate total phenolic content (TPC), total anthocyanin content (TAC), and antioxidant activities of white, brown, and black rice crackers. Additionally, the study evaluated changes in these parameters following simulated in vitro digestion. The identification of specific phenolic compounds within the rice crackers was carried out using high-performance liquid chromatography (HPLC). Moreover, the study explored the inhibitory effects of these phenolic compounds on the enzymatic activities of α-amylase and α-glucosidase. The findings revealed that black and brown rice crackers consistently displayed higher TPC, TAC, DPPH, and FRAP values compared to white rice crackers. In vitro digestion led to substantial TPC release, approximately 3.81-4.95 times higher, significantly increased DPPH values by 14.96-24.14 times, and elevated FRAP values by 4.25-4.90 times (p < 0.05). However, there was a reduction of TAC values following digestion. HPLC analysis indicated the presence of various phenolic compounds, including gallic acid, 2,5-dihydroxybenzoic acid, catechin, vanillic acid, rutin, p-coumaric acid, p-hydroxybenzoic acid, ferulic acid, and quercetin, in brown and black rice crackers, while white rice crackers primarily contained gallic acid and 2,5-dihydroxybenzoic acid. Furthermore, brown and black rice crackers exhibited stronger inhibitory effects on α-amylase and α-glucosidase compared to white rice crackers, with lower IC50 values. These findings highlight substantial variations among the different rice varieties, indicating the potential of brown and black rice for the production of rice crackers with lower glycaemic responses, higher nutritional value and the potential health benefits associated with enhanced phenolic composition and strong inhibitory effect on carbohydrate-digesting enzymes. Protein is essential for tissue growth, repair, and maintenance, as well as the production of enzymes, hormones, and antibodies, contributing to metabolic processes, bodily functions, and immune system function (Wu, Gao, Yu, & Wang, 2022). In response to the prevalent protein insufficiency in white rice crackers, a novel research avenue involves the formulation and advancement of protein-fortified rice crackers. Oysters (Crassostrea gigas) and mussels (Perna canaliculus) are valuable seafood resources consumed widely in New Zealand and contain higher levels of easily digestible protein and iron compared to traditional fish and red meats (Yaghubi et al., 2021). Oyster and mussel proteins are explored for functional foods and supplements, providing essential amino acids and potential health gains. Mussel proteins aid tissue engineering and drug delivery via biocompatibility and adhesion. Oyster proteins offer nutraceutical potential, aiding heart health, immunity, and antioxidants (Harnedy & FitzGerald, 2012; Ulagesan, Krishnan, Nam, & Choi, 2022). Fortifying white rice crackers with oyster and mussel proteins presents an opportunity to boost their nutritional content, lower glycaemic impact, and introduce potential bioactivity, including noteworthy antioxidant capacity and functional effects on inflammatory responses. This study evaluated the overall enhancement in the quality of crackers fortified with oyster and mussel powder at concentrations of 5%, 10%, and 20%, and assessed their impact on glycaemic response and protein bioaccessibility using in vitro starch and protein digestion assays. Additionally, antioxidative capacity was examined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and the Ferric Reducing Antioxidant Power (FRAP) assay. Results indicated that oyster and mussel powders inclusion led to a substantial reduction in starch content, resulting in a decrease of approximately 30% in glucose release and area under the curve (AUC) values during starch digestion compared to the control sample (white rice crackers). Furthermore, the addition of oyster and mussel powders significantly (p < 0.05) increased TPC, with values ranging from 16.74 mg GAE/100g sample to 104.90 mg GAE/100g sample in 20% oyster enriched sample and 77.65 mg GAE/100g sample in 20% mussel enriched sample. Moreover, the release of phenolic compounds during gastric and intestinal digestion was enhanced by nearly 150% and 50%, respectively, compared to the control sample. Antioxidant activity (DPPH and FRAP value) of enriched crackers also exhibited a significant increase corresponding to higher oyster and mussel powder incorporation. However, despite the increase in protein levels from 6.36% to 12.60%, protein digestibility declined from 77.64% to 63.05%. This reduction could be attributed to interactions between phenols and proteins in the samples, potentially affecting overall protein digestion. Furthermore, to evaluate protein availability and bioaccessibility, the research examined alterations in soluble protein content and amino acid composition after in vitro digestion and assessed the protein quality using the Digestible Indispensable Amino Acid Score (DIAAS). Additionally, the study evaluated bioactive peptides by measuring ACE inhibition and anti-inflammatory effects using LPS-stimulated RAW264.7 macrophages. Outcomes revealed heightened protein content and soluble protein content following digestion in oyster and mussel-enriched samples (oyster20, mussel20) compared to the control. Amino acid analysis showcased the increased release of essential and non-essential amino acids during digestion in enriched samples. DIAAS analysis underscored enhanced amino acid bioavailability in enriched rice crackers. Notably, molecular weight distribution exhibited the formation of smaller peptides during digestion. ACE inhibitory activity displayed significantly elevated values in enriched samples, suggesting potential cardiovascular benefits. Anti-inflammatory assessments demonstrated decreased NO production and pro-inflammatory cytokine levels in enriched samples compared to LPS-induced RAW 264.7 macrophages. Overall, this study underscores the significant variations among rice varieties and emphasizes the potential of brown and black rice for producing crackers with enhanced nutritional value, lower glycaemic responses, and health-promoting phenolic compounds. The exploration of marine-based protein fortification further offers a promising avenue for improving rice cracker quality and bioactivity. Through comprehensive analyses, this research contributes to a better understanding of the potential benefits and quality improvements that can be achieved through innovative approaches in rice cracker production.
Open Access
Formulation of pasture seed mixtures with emphasis on the effect of nitrogen fertilisation : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2023) Myint, Thinzar Soe
The aim of this study was to determine the optimal proportions of pasture mixtures and amounts of seed and nitrogen fertiliser (N) to maximize yield and quality. Three monocultures and seven species mixtures, that differed widely in their proportions (0 to 1) of perennial ryegrass, white clover and plantain were sown at 1,000 and 2,000 viable seeds/m2 and with either 0 or 225 kg N/ha/year. Plots were drilled in 2.1 x 6 m plots on 31 March 2017 and measured for four years. The plots were grazed in common by sheep eight times annually (except the first defoliation after sowing when they were cut) and irrigated when required. Herbage accumulation and its proportions of sown species and weeds were determined at each harvest over four years (2017/2018–2020/2021); nutritive value (metabolisable energy (ME), crude protein (CP) and neutral detergent fibre (NDF)) over three years (2018/2019–2020/2021), and light interception and radiation use efficiency (RUE) over two years (2018/2019–2019/2020). To quantify the fractional intercepted radiation of pastures, an accurate method of measuring light interception was investigated. Fractional intercepted radiation was measured or predicted using a SunScan plant canopy analyser, GreenSeeker handheld sensor, rising plate meter (RPM), destructive harvests, and the combinations of SunScan and GreenSeeker, and SunScan and RPM. A hybrid method of SunScan and RPM (fractional light interception values ≤0.3 of SunScan were replaced with the predicted values using RPM) was chosen as an accurate method based on the parameters of extinction coefficient, critical LAI, R2 values, standard errors of regression. Response variables were quantified using diversity-interaction modelling to quantify effects of species ‘identity’ (monoculture performance or average monoculture performance of species in the mixtures) and ‘diversity’ (the excess of mixture performance over that expected from average performance of species in the mixtures). Seed density did not influence species identity and diversity effects on pasture yield and quality in any year. The annual total dry matter yields of ryegrass and plantain averaged over four years were 16.8 and 16.6 t DM/ha/year without N fertiliser, and 19.1 and 18.9 t DM/ha/year with N. White clover had the same production (14.9 t DM/ha/year) ± N. Mixtures produced diversity effects (additional dry matter yield). The highest extra dry matter yield (4.32 t DM/ha/year) among binary mixtures was obtained from the ryegrass-white clover mixture at the average of two N treatments. Three-species mixtures needed N to produce higher extra yield than binary mixtures. The extra benefit produced by the equal-proportional mixture of three species with N was 5.20 t DM/ha/year. The annual weed yield was lowest in perennial ryegrass (1.68 t DM/ha/year) at average N (average of 0 and 225 kg N/ha/year). The weed yield of ryegrass reduced from 2.16 at the –N level to 1.2 t DM/ha/year at the +N level. There was no N effect on weed yields of white clover and plantain. Mixtures reduced weed yield, and the highest amount of weed reduction was found in the even three-species mixtures (3.28 t/ha/year). Nutritive values were likely to be a function of identity effects and there was no effect of N. At average N, ME was higher in perennial ryegrass (11.0 MJ kg/DM) and white clover (11.0 MJ kg/DM) than in plantain (10.7 MJ kg/DM). CP was higher in white clover (25.7%) than plantain (20.5%) and perennial ryegrass (19.2%). Higher neutral detergent fibre (NDF) was found in perennial ryegrass (47.8%) than plantain (36.3%) and white clover (35.0%). After four years, an equi-proportional mixture of perennial ryegrass and white clover, based on seed count and equivalent to 12 kg PR and 7 kg WC (19 kg total coated seed)/ha at the low seed density (1000 seeds/m2), produced an optimal balance of increased total yield (20.6 t DM/ha/year), weed suppression (3% of total yield), ME (11 MJ/kg DM), CP (21.7%) and NDF (44%) at the –N level. The optimal mixture at the +N level was the three-species mixture with the proportion of 0.4 PR: 0.3 WC: 0.3 P equivalent to 9.60 kg PR, 4.20 kg WC, and 6.0 kg P (19.8 kg total coated seeds/ha) at the low seed density. It produced 23.0 t DM/ha/year with no weed, 10.8 MJ ME kg/DM, 19.5% CP, and 46.1% NDF. The equi-proportional seed mixture of perennial ryegrass and white clover changed to a mixture of 71% ryegrass, 26% white clover, and 3% weed as the actual proportions in the sward averaged over four years, yielding 20 t DM/ha/year. At the +N level, all three species mixtures, which changed to ryegrass-dominant mixtures in a four-year period, remained the highest-yielding mixtures, producing 20.8–22.4 t DM/ha/year. Differences in dry matter yield among mixtures were fully explained by the combined effect of light interception and radiation use efficiency (RUE). The optimal mixtures ±N that maximised intercepted light and RUE simultaneously were the same mixtures that produced maximum dry matter yield. They provided 188 and 170 MJ/m2/year more intercepted photosynthetically active radiation (PAR) and 0.23 g DM/MJ PAR more RUE. This study provided the two optimal seed mixtures for ±N level that maximised total dry matter yield with high quality and minimised weed yield under irrigated conditions. The dry matter yield differences among monocultures and mixtures were explained by the accumulated intercepted PAR and RUE. Moreover, there was an observation that accumulated intercepted PAR and RUE values changed depending on the methods used to measure light interception.
Embargo
Livelihood goals, livelihood strategy selection and household welfare in rural China: A utility maximization perspective : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2023) Chen, Chen
China has the world’s second largest rural population and dramatic development in the rural economy. Rural households’ livelihoods have changed with economic transformation and face challenges from income equality, relative poverty, climate change and the continuing influence of COVID-19. In this situation, how to realize inclusive, sustainable and resilient livelihoods for rural residents is an urgent problem. Rural households’ livelihood decision largely results from unobserved heterogeneous goals and intentions and directly observable, different rural household characteristics. Previous studies explored the factors influencing rural households’ choice of a livelihood strategy and livelihood outcome but mainly focused on the impacts of external macro factors. However, livelihood goals are emphasized as the main base for rural households to allocate livelihood assets and are the critical orientations of livelihood strategy selection. To date, it is still poorly understood how rural households’ livelihood goals influence their livelihood strategy selection and whether different livelihood goals and their potential interaction effect with livelihood strategy selection influence rural household welfare. Using the panel data from the 2010-2018 China Family Panel Studies, this study explores the relationship between livelihood goals, livelihood strategy selection and rural household welfare. After deleting cases with missing values in the main and control variables, 23,967 rural cases are used for analysis in the study. To explore the linkages between livelihood goals and livelihood strategy selection, this study constructs measurements of three livelihood goals (the survival, security and self-respect goals) and then calculates an index for each goal. Livelihood strategies are divided into three groups (agricultural, non-agricultural, and diversification) based on rural households’ income sources. The multinomial logit model with fixed effects empirically estimates the relationship between livelihood goal indices and livelihood strategy selection. The random effects and the correlated random effects models are used to check the robustness. The two-step instrumental probit regression model is used to address the endogeneity problem. The results show that rural households with a survival goal are more likely to choose the diversification and agricultural strategies but less likely to select the non-agricultural strategy. In contrast, the non-agricultural strategy is the priority when rural households pursue security or self-respect maximization. To address potential endogeneity in the dynamic panel model, the generalized method of moments model is used to investigate the impact of livelihood goals and strategy selection on rural household welfare. The unconditional quantile regression with fixed effects model is employed to analyse the heterogeneous effects on household welfare. The results show that rural households with a higher livelihood goal do not obtain higher welfare. Rural households adopting the non-agricultural and diversification strategies have higher welfare than other strategies. The interaction effects show that rural households can get higher welfare if their livelihood goals and livelihood strategy selection match. The unconditional quantile regression result shows that households’ livelihood goals and livelihood strategy selection affect household welfare across different quantiles.
Open Access
The biological control of the red clover casebearer in New Zealand : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2024) Faulkner, Joel
Biocontrol of insect pests represents an important aspect of sustainable crop management that has potential to reduce the current reliance on chemical control measures. However, often the potential of all forms of biocontrol is undermined in contemporary productive systems and their resulting landscapes. In New Zealand seed three species of clover feeding moths of the Coleophora genus have seriously hindered red and white clover seed production during the last 100 years in New Zealand. From the 1920s until the 1960s two species of white clover casebearer (Coleophora mayrella and C. alcyonipennella) caused varying levels of seed yield reduction in white clover seed crops. During the 1960s efforts were made by government science agencies to establish parasitoid wasps of these species. This programme was highly successful, resulting in the total suppression of clover casebearer seed pests in New Zealand, until the arrival of the red clover casebearer (C. deauratella) during 2016. This pest quickly spread throughout the country’s clover growing regions, leading to yield reductions. This thesis explores the arthropod community of red clover seed crops under a main theme of ‘the biocontrol of the red clover casebearer’. The experiments employed are varied, although typically with a major aim being exploring the function of species within the red clover seed crop ecosystem. Three species of parasitoid wasp were able to successfully use C. deauratella as a host; Bracon variegator, Pteramalus puparum and Eupelmus (Macroneura) messene. The red clover casebearer was clearly undergoing remission as a pest and only two damaging populations of this pest could be located. The predominant parasitoid, B. variegator, had a field parasitism incidence of up to 75% on C. deauratella, but despite this these two populations of the pest persisted. Over the course of these experiments it was noted that a fungal growth was leading to mortality of C. deauratella larvae. From infected C. deauratella cases a potentially entomopathogenic strain of Fusarium pseudograminearum was isolated and identified through PCR sequencing. It is still uncertain how C. deauratella is being regulated in New Zealand red clover seed crops. The role of parasitoid wasps, a potential fungal pathogen and other unknown biocontrol agents is yet to be determined.
Open Access
Understanding the growth and development of maize (Zea mays L.) : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University
(Lincoln University, 2024) Mwayawa, Annette
A main constraint to maize production in New Zealand is yield variability due to the low rainfall supply and also the erratic distribution of rain in the summer which consequently affects crop N uptake and utilization. The aim of this study was to understand the influence of N and water on canopy development, crop growth, phenological development and yield formation. Crops with different yield potentials were created using different levels of N and water availability. Two experiments were carried out, marking the growing season, Experiment 1 in 2015/16 and Experiment 2 in 2016/17. The two experiments were carried out at two different locations at Lincoln University, Canterbury, New Zealand. Experiment 1 was arranged in a split-plot design with four nitrogen (N) levels under different water regimes. The N levels were N1- nil, N2 -75 kg N/ha, N3 – 150 kg N/ha and N4 – 300 kg N/ha, and water levels at Irr1- Irr4 as defined by the accumulated potential soil moisture deficit as 443 (rainfed), 367, 301 and 226 mm, respectively. These created grain yields that were not different in all the treatments which averaged 12.4 t/ha and only varied in total dry matter (DM) accumulated. To create more distinct differences in grain yield, this experiment was repeated at another location with a higher dose of N. Experiment 2 used two levels of water and N in a randomised block design. The treatments were for N1 –nil N and N2 - 500 kg N/ha, rainfed and irrigation (accumulated potential soil moisture deficit at 536 and 296 mm respectively). In Experiment 1, grain yield was not different across the crops and average 12.4 t/ha. The total DM was 19.1 t/ha for the rainfed crop (Irr1) and averaged 22.4 t/ha for the irrigated crops. Grain yield and total DM as explained by intercepted photosynthetic radiation (iPAR) accumulated to 570 MJ/m2 for Irr1 and was higher at 1082 MJ/m2 for Irr2. All crops GAI reached a maximum at 3.7 m2/m2 at a rate of 0.01 m2/m2/°Cd in the duration of 677 °Cd which justified the similarities in grain yield. After the linear phase, the intercepted light in Irr1 immediately reached an asymptote as the leaves withered quickly due to water stress. The radiation use efficiency (RUE) was 2.21 g/MJ for N1 and 2.49 g/MJ for N4 and mainly because of the specific leaf N (SLN). The SLN was highest at 2.1 g N/m2 for the irrigated crop with N and lower at 1.66 g N/m2 without N. The contribution of SLN to yield was reflected in total DM. In Experiment 2, grain yield increased progressively from 0.98 t/ha under rainfed to 9.0 t/ha when irrigated and further to 16.3 t/ha with N. Total DM followed a similar response with rainfed accumulating only 4.10 t/ha and 14.3 t/ha under irrigation and doubling with N, creating total DM of 28.9 t/ha. The difference in total DM was explained by the differences in the total amount of iPAR. Under rainfed the total iPAR was 448 MJ/m2 and increased to 551 MJ/m2 with N, and when irrigated was 816 MJ/m2 and further increased to 1005 MJ/m2 with N. The rate and duration changed, indicating the capacity of the crop to capture light depended on the changes in pigment protein complexes, directly linked to development of the GAI as a process of leaf development and expansion. The maximum GAI was affected by the main effects of water and N where GAI increased from 2.14 to 3.49 m2/m2 with water and from 2.48 to 3.14 m2/m2 with N application. In the contribution of RUE to grain yield, SLN was a key factor connecting leaf N concentration to DM production. The SLN was 1.23 g N/m2 at 905 °Cd in all the crops, however, dissecting the canopy into cohorts, SLN varied. The main section of the canopy that supplied assimilates directly to ear development was the mid-cohort. This cohort was affected by both water and N, increasing SLN from 1.43 to 2.39 g N/m2 with water and from 1.46 to 2.37 g N/m2 with N. The changes at cohort levels were explained by GAI as parameter relating to canopy development and the allocation of N within the leaf, and light penetration through the hierarchical canopy arrangement. The amount of water used to produce the given yield in Experiment 2 depended on crop water use which was converted to WUE. Only the crop under irrigation and N was efficiently converting water to DM at 47 kg DM/mm of water. The WUE for the rainfed crops was 17.9 kg DM/mm and did not differ from the irrigated crop without N which had a WUE of 25.7 kg DM/ha/mm. Leaf and canopy photosynthesis has led to improvements in crop DM and yield through enhanced DM partitioning. In depth understanding into elements of SLN is essential for estimation of the SLN throughout the cropping season. The future of crop improvement strategies is dependent on maximising the leaf and canopy photosynthesis and converting DM accumulation into yield benefits.

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