Browsing by Author "Roskruge, Nick"

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Abiotic stress effects associated with climate change on yield and tuber quality of potato cultivars in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science, School of Agriculture and Environment, Massey University, Manawatu, New Zealand
(Massey University, 2021) Siano, Allan
The recent weather anomalies in New Zealand, particularly the summer heatwaves of 2017/18 and 2018/19, hottest and third hottest on record, respectively, have seemingly affected potato production. The purpose of this research is to determine how abiotic stress commonly associated with climate change, e.g., drought and heat, is affecting the current potato production in New Zealand, define its effects on yield and tuber quality of commercial potato cultivars, and determine if cultivars exhibit differential susceptibility. Secondary climate data in the past 60 years (1958–2018) during the potato growing months of October to March showed an increasing trend for temperature in Ohakune (+0.53 °C), Opiki (+0.36 °C), and Hastings (+0.28 °C) as well as a decreasing trend for rainfall in Ohakune (-24.8 mm) and Hastings (-48.7 mm). The increase in temperature also increased the number of days with supra-optimal atmospheric temperatures believed to delay (>25 °C) or inhibit (>30 °C) tuber growth in Hastings by 57 days (2017/18 season) and in Opiki by 103 days (2018/19 season). Baseline data from a preliminary study during the 2017/18 growing season showed that abiotic stress associated with the extreme weather conditions apparently affected the yield and tuber quality, with cultivars showing differential susceptibility. Up to 85% unmarketable tubers were recorded among the samples collected, which was attributed to the high incidence of a wide array of tuber physiological disorders. The multi-environment trial in the 2018/19 growing season showed that abiotic stress had significant effects on the different morpho-agronomic and physiological functions of the potato crop and ultimately affected the yield and tuber quality. Abiotic stress increased the incidence of tuber physiological disorders, e.g., tuber malformation, growth cracks, and second growth, which reduced the total yield and marketable yield by up to 43.3% and 45.1%, respectively. Additionally, genotype × environment analysis showed that cultivar ‘Taurus’ is the most stable and adaptable cultivar across trial sites (wide adaptation). At the same time, cultivars ‘Hermes’ and ‘Snowden’ are tolerant to heat and drought stress (Opiki) and heat stress alone (Hastings) (specific adaptation), respectively. The glasshouse and plant growth chamber trial revealed that drought stress (DS) generally reduced the plant height, number of leaves, and canopy cover but enhanced the formation of more but smaller stomata and glandular and non-glandular trichomes. DS also encouraged the closing of the stomatal aperture potentially to reduce water loss, thereby reducing the transpiration rate (E), stomatal conductance (gS), and net photosynthesis (PN), which potentially affected the final yield. Conversely, heat stress (HS) increased the plant height, canopy cover, and number of leaves and developed more and larger stomata. HS also stimulated stomatal opening, leading to enhanced E and gS and improved PN at the vegetative stage. On the other hand, in general, the combination of drought and heat stress exacerbated the adverse effects of each abiotic stress type on the different morpho-physiological parameters. As established in the various component trials of this research, different abiotic stresses associated with climate change have a significant effect on the morpho-agronomic and physiological functions of potato crops and negatively impacts the yield and tuber quality. Breeding of new cultivars, and mass selection of existing cultivars should be conducted through multi-environment trials to identify adaptable cultivars that can be used to mitigate the effects of abiotic stresses associated with climate change on potato crops in the field and to increase the resiliency of the New Zealand potato industry.
Effect of traditional storage methods on post-harvest dormancy of Taewa Māori seed potato (Solanum tuberosum L.) in Aotearoa New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science, School of Agriculture and Environment, Massey University, Manawatu, New Zealand
(Massey University, 2024) Sousa Carvalho, Marcos Schleiden
In the Solanaceae family, the potato (Solanum tuberosum L.) is one of the major tuber crops. In New Zealand there are potatoes called Taewa. Māori growers who grow these potatoes generally store the harvested seeds in dark places, at the ambient temperature and a large proportion of those growers generally store with dry fern coverage for at least four months before planting. The objective of this study was to evaluate the Māori storage method on the preservation of the seed potatoes. This experiment chose conditions to represent traditional methods, the major difference being temperature control. The Māori Storage Method (ambient and dark environment) was contrasted with the Conventional Storage Method for potatoes, which consisted of placing the potato seeds in a dark room at continuous temperature of 5˚C. The potato seeds used in the experiment were randomly selected, weighed. And then put into storage. Tubers were evaluated at 30-day intervals from the beginning to 120 days of storage. A randomized complete block design was applied with 3 blocks of the treatments. In the first experiment (2022), analyses of respiration rate, weight loss and sugar content were performed. In 2023 the same experiment was repeated with some changes i.e., measuring sprouting (length, width and number of sprouts in Taewa varieties), but not sugar content (SC), and doing respiration rate (RR) and weight loss (WL) again for comparison between the two trials. Data on the evaluated parameters were analysed using a linear mixed model (Mixed Procedure) with year, variety, storage method and their interactions as the fixed factors and block as the random factor following by a Tukey-Kramer test for multiple comparisons. An exponential regression model (Nlin Procedure) was applied to fit the data on the change of parameters evaluated, and the coefficients of determination (R2) for regressions were also calculated. The response variables (respiration rate, weight loss, and sugar content) presented characteristics of each variety, highlighting the Tutaekuri variety with the highest respiration rate and percentage of sugar content. The variety that showed the highest percentage of weight loss was Moemoe. The influence of environmental conditions during the storage period of the Māori method may have interfered with the dormancy period of Taewa potatoes in the response variables (respiration rate, weight loss, sugar content, and sprout). The tuber dormancy duration is largely dependent on the genotype along with pre-and postharvest conditions. The factor that most determined this characteristic was the storage temperature. In this experiment, storage temperature is the main environmental factor affecting tuber dormancy on Taewa potatoes. The tuber dormancy duration is largely dependent on the genotype along with pre-and postharvest conditions. In general, there is a lot of common ground between both cultural and commercial approaches to seed selection and storage.
Hokia ki te whenua : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand
(Massey University, 2007) Roskruge, Nick
This thesis aIms to produce a distinctive model for the sustainable horticultural development of Maori resources, primarily land. It is inclusive of tikanga Maori and indigenous production systems based on the unique body of knowledge aligned to Maori. The integration of this knowledge with western science is both argued and applied through the model itself. The hypothesis applied was that matauranga Maori relevant to horticulture and pedology can inform and add value to the future development of Maori land resources. The thesis is bui lt on a unique set of contributing knowledge bases aligned to soils and horticultural management supported by three case studies, identified through their common association i.e. whakapapa links. The format of the thesis intentionally follows science principles in structure and presentation and some assumptions are made regarding base knowledge surrounding Maori cultural factors and the science disciplines relative to soils and horticul ture. The indigenous element, including Maori knowledge, is incorporated into the model using a triadic kosmos/corpus/praxis approach. Where kosmos is applied as Te A o Miiori, corpus as miitauranga Miiori and praxis as tikanga Miiori, the relationship between each element is clear and the interpretation of the associated knowledge becomes more apparent and can be applied to cultural assessments of resources, i ncluding land. The crux of the cultural assessment model is the quality of information used to assess Maori resources, especially from the cultural perspective. The Maori cultural paradigm, traditional horticulture and pedology, and various decision systems are purposefully accessed to act as contributors to the assessment model and to highlight the diversity and quality of information land managers have at their disposal. The ability to apply a cultural layer drawn from a body of knowledge not previously included in decision models relative to land utility in New Zealand is the key point. of difference of the model. The model is discussed from the perspective of its beneficial role for future use by Maori and how it can be continuously refined to meet the needs of Maori land owners and thus contribute to the rangatiratanga of Maori.
The contribution of kumala to traditional food systems in two districts of Tanna Island, and its potential for increasing food security : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Horticulture and Ethnobotany at Massey University, Palmerston North, New Zealand
(Massey University, 2024) Nasse, Amanda
Sweetpotato (Ipomea batatas) is considered a versatile food crop owing to its robust adaptability to diverse soil conditions and environmental conditions. In Vanuatu sweetpotato is a significant food security crop that smallholder farmers cultivated within traditional cropping system. Within the national and local context, sweetpotato has played a significant role as recovery crop that supports the farmers and increasing urban population buffer against food scarcity during the aftermath of natural disasters. The research reported in this thesis examined and explored how kumala (sweetpotato) contributed to smallholder farmers livelihood and enhanced food and nutrition security. The aim of the study was to understand the significant role of kumala within the traditional food system and draws on smallholder farmers perspectives. Storian is the overarching cultural approach that underpinned the research process in this study, supported with the use of qualitative methods of collecting data these included, semi structure interviews, secondary data, and field observation. Subsequently the data collected through the interviews and storian were analysed using qualitative data analysis. The research study was carried out in Tanna Island, a society with stronghold of traditions and cultural activities that are interwoven in the livelihood of smallholder farmers influencing the farmers perception on the production of kumala. This research highlights kumala is a favoured food security and recovery crop featured as response to recovery program. Kumala has a role in the traditional food system which is enhanced by existing social and cultural ties. The study put forward a critical perspective on leveraging on short term resilient crops that emerge through strengthening and revitalize the role of kumala within the local food system can strengthen household resilience and enhance food security for smallholder farmers.