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    A study of the influence of spacing within rows and seed tuber size upon the yield of the potato crop : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agriculture Science at Massey University
    (Massey University, 1966) Anang, Husin
    The potato is one of the main food crops grown in New Zealand, and has been established since the time of European settlement In the early years production was concerned mainly with meeting the demands of the growing population. This resulted in a rapid and steady inorease in the total acreage grown. However, in the last decade, increase has been gained largely through intensification of orop areas rather than their extensification. Consequently, a diminishing increase in acreage grown has resulted. The above pattern is clearly illustrated in the following figures (extracted from Farm Production Statistics of New Zealand 1963 - 1964) [From Introduction]
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    A study of the influence of spacing within rows and seed tuber size upon the yield of the potato crop : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agriculture Science at Massey University, New Zealand
    (Massey University, 1966) Anang, Husin
    Undoubtedly there is a need for more intensive research on improving methods of growing potatoes. One aspect which has a major influence on plant population is seed spacing and seed size. The project reported herein was designed to study the effect of different levels of spacing and seed size, together with their interactions, on terminal yield of potato crops. In view of the need to study other important factors influencing yield, the investigation was extended to include the effects of seed spacing and size on growth and development of the crops.
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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.
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    Investigation of genotype and phenotype interactions using computational statistics : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Statistics at Massey University, New Zealand
    (Massey University, 2021) Angelin-Bonnet, Olivia
    Deciphering the precise mechanisms by which variations at the DNA level impact measurable characteristics of organisms, coined phenotypes, through the actions of complex molecular networks is a critical topic in modern biology. Such knowledge has implications spanning numerous fields, from plant or animal breeding to medicine. To this end, statistical methods must be leveraged to extract information from molecular measurements of different cellular scales, allowing us to reconstruct the regulatory networks mediating the impact of genotype variations on a phenotype of interest. In this thesis, I investigate the use of causal inference methods, to infer relationships amongst a set of biological entities from observational data. More specifically, I tackled the reconstruction of multi-omics molecular networks linking genotype to phenotype. In the first part, I developed a simulator that generates benchmark gene expression data, i.e. RNA and protein levels, from synthetic gene regulatory networks. The originality of my work is that it includes transcriptional and post-transcriptional regulation amongst genes. I used the developed simulation tool to evaluate and compare the performance of state-of-the-art causal inference methods in reconstructing causal relationships between the genes. The evaluation focused on the ability of the methods to reconstruct relationships mediated by post-transcriptional regulations from observational transcriptomics data. I also evaluated the methods performance to detect different types of causal relationships between genes via a catalogue of causal queries, and highlighted the shortcomings associated with using transcriptomics data alone in reconstructing gene regulatory networks. In the second part, I developed an analysis framework to shed light on the biological mechanisms underlying tetraploid potato tuber bruising. I first integrated a GWAS analysis with a differential expression analysis on transcriptomics data, to uncover genomic regions in which variations affect the response of tubers to mechanical bruising. I then used a multi-omics integration tool to jointly analyse genomics, transcriptomics, metabolomics and phenotypic data and to identify molecular features across the omics datasets involved in tuber bruising, including some not identified with traditional differential expression analyses. Finally, I made use of causal inference tools to reconstruct a multi-omics causal network linking these features to decipher the molecular relationships involved in tuber bruising. I used causal queries to extract information from the reconstructed causal networks and interpret the uncovered relationships.
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    Starch retrogradation in tuber : mechanisms and its implications on microstructure and glycaemic features of potatoes : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in School of Food and Advanced Technology at Massey University, Palmerston North, Manawatū, New Zealand
    (Massey University, 2020) Chen, Yu-Fan Nicole
    An increase in the occurrence of diabetes mellitus, cardiovascular disease and obesity in recent years led to the project “Starch retrogradation in tuber: mechanisms and its implications on microstructure and glycaemic features of potatoes”. Potato products can play a role in mitigating these hyperglycaemic events, if starch in these processed products is slowly digested and/or starch-derived glucose is released into the circulation in a slower and more attenuated manner. Three stages were envisaged for the project with an aim to create slowly digestible starch in whole potato tuber (in tuber) through starch retrogradation. Plant-based whole food systems, such as potato tubers encompass different cell compartments, (e.g. cell wall, vacuole, cytoplasm and intracellular spaces) within which starch gelatinisation and retrogradation occur, subject to local interactions of other cell components and water availability. Structural changes of potato starch during retrogradation in tuber and its resulting digestibility were studied. Different water pools in a cooked whole tuber were discerned by the low-field NMR (LF-NMR), having relaxation times T20 at <1 ms, T21 at 10-15 ms, T22 at 70–200ms, and T23 at > 400 ms. A significant reduction in eGI was observed after cooling and storage compared to freshly cooked tubers. Reheating of retrograded tuber restored some of the susceptibility to enzymatic hydrolysis and internal water mobility. Longer chilled storage (7 days) yet improved the stability of retrograded tuber against reheating effects (at 90 °C). Realignment of the gelatinised amylose and amylopectin changed the distribution of crystalline and amorphous regions during refrigerated storage and subsequent reheating, resulting in starch digestibility varying with treatment combination. Several, but not all, of time-temperature cycle processes were observed to induce stepwise nucleation and propagation, facilitating starch retrogradation in tuber more than did storage fixed at 4 °C. Sous vide processing (at 55 and 65°C), akin to annealing, combined with starch retrogradation in tuber, resulted in potatoes with intermediate eGI (40-72). After reheating at 60°C, the eGI of sous vide cooked-chill potatoes increased moderately, displaying a mixture of partially gelatinised starch and swollen granules. Food processing, i.e. optimum TTC process or sous vide process might facilitate the formation of retrograded starch in tuber, resulting in a reduced eGI (than freshly cooked tubers). To retain the resistance to digestive enzymes in retrograded starch in tuber, reheating at low temperatures (50-60°C) were needed.
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    A study of the alternaria leafspot complex on potatoes and tomatoes in the Manawatu : this thesis is presented as partial fulfillment of the requirements for the M. Agr. Sc. degree of Massey University College of the Manawatu.
    (Massey University, 1963) Hawthorne, Brian Tredinnick
    The fungus Alternaria (Macrosporium) solani is associated with a foliage disease of potatoes and tamatoes throughout the world. Although there are often several phases of attack on these hosts by the fungus e.g. tuber damage in the potato and seedling loss with tomatoes, the disease has been named on the basis of the foliage symptoms which are characteristic. Two names are commonly used (l) Target Spot (2) Early Blight, and of the two, 'Target sport' is the more descriptive since foliage lesions are circular to irregular dark brown areas with a very characteristic zonation effect due to a series of more or less concentric rings within the lesion. [From Introduction]
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    Investigations into the nutritional and sensory potential of taewa (Māori potatoes) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy, Nutritional Science, at Massey University, Palmerston North, New Zealand
    (Massey University, 2015) Wharemate, Zirsha R
    The term Taewa refers to a collection of at least 18 different potato cultivars belonging to the Solanum tuberosum family, which have been cultivated by the Maori peoples of New Zealand for at least 200 years. Due in part to its economic importance worldwide, the chemical and nutritional composition of today’s mainstream potato varieties, and the mechanisms by which composition impacts on their culinary and gastronomic properties, have been extensively researched. However few investigators have studied the nutritional, sensory or potential health properties of Taewa, or which Taewa varieties may be the most preferred for eating. Previous Taewa nutritional research has concentrated on anthocyanin, phenolic or flavonoid content and antioxidant potential, glycoalkaloid content and starch characteristics. The variation in culinary quality and different tuber pigmentation of Taewa suggest that the composition, nutritional and sensory properties of Taewa are diverse and are therefore worthy of investigation. The first goal of the PhD focused on identifying nutritionally beneficial or commercially viable properties of Maori potatoes. This was carried out by quantifying the macronutrient, selected micronutrient, phenolic and glycoalkaloid components and assessing antioxidant activity (using ORAC and FRAP analysis) of four Taewa varieties (Huakaroro, Karuparera, Moemoe, Tutaekuri) and comparing them against Nadine, a potato variety commonly available in New Zealand. Analysis was carried out on tuber flesh, tuber skin and whole tuber components over two consecutive harvests. In addition, the effects of 6 months storage at 4oC in 80-90% humidity and par-boiling on the nutrient content were also explored. The second goal of this research was to ascertain the most popular, commonly eaten and commonly grown Taewa varieties; preferred Taewa cooking and eating practices; the availability of Taewa cultivars across New Zealand and to collate information regarding marketable traits or factors that might affect Taewa consumption. In order to achieve this, group discussions were held with 25 adult participants between 18 to 75 years of age from the Manawatu region. Four key themes emerged from these discussions and were used to develop 20 questions for a larger scale survey from a wider crossection of Taewa consumers. The third goal of the research aimed to assess two characteristics of nutritional or health value (increased resistant starch in potato boiled then cooled at 4oC for 24 h) and antioxidant capacity (by measuring the total phenolic content, DPPH and FRAP potential) in four common Taewa varieties (Huakaroro, Karuparera, Moemoe, Tutaekuri) using a popular Taewa cooking practice (boiling whole with the skin on) to develop a Taewa product with improved health benefits. Consumer acceptance was then measured by assessing the sensory ratings of 56 adult volunteer subjects. Results of the nutrient analysis consistently showed all four Taewa had promising nutritional value with regards to a greater nutrient content, greater accumulation of resistant starch, greater total phenolic content and antioxidant capacity compared to Nadine. The nutrients in Taewa likely to be of most biologically significant nutritional value in comparison to Nadine and other more common NZ potato cultivars included the soluble and insoluble fibre content, the minerals potassium, magnesium and iron and the vitamins thiamine, pyridoxine and niacin. All four Taewa (particularly Tutaekuri) also showed excellent potential with regards to accumulating resistant starch and exhibiting antioxidant potential compared to Nadine. Commonly eaten Taewa varieties included Tutaekuri, Pawhero, Peruperu, Moemoe, Karuparera and Huakaroro. These Taewa varieties were also grown and eaten by residents in a greater number of regions across New Zealand than other Taewa varieties. Cooking and eating preferences included boiling them whole, unpeeled and cooked on their own; eating them hot or warm, with the skin on and seasoned with butter, salt and pepper. If destined to be pre-cooked or served cold, it was suggested that Taewa varieties should be waxy so as to hold together better, be purple or buttery-yellow to add interest with regards to visual appeal, be an appropriate size for the intended dish and have a sweet, nutty, buttery or delicate taste. New Zealanders should be encouraged to both eat and grow Taewa due to their value as a popular inexpensive food of high nutritional quality, their promise as a means through which to develop functional food products with added health benefits and their cultural significance to all New Zealanders as a unique heritage food. Government agencies, those involved in the Potato Industry, research institutions and funding agencies should be encouraged to work with Maori growers, to ensure the increased production and nationwide availability of Taewa and support the development of Taewa-based functional and snack food products in way that will be beneficial to all.
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    Comparison of heritage and modern crop cultivars in response to irrigation and nitrogen management : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science, Institute of Natural Resources, Massey University, Palmerston North, New Zealand
    (Massey University, 2012) Fandika, Isaac Rhinnexious
    There is a resurgence of interest in heritage crop cultivars (potatoes, squash and yams) in New Zealand because of the premiums farmers get at niche markets. However, a paucity of information in relation to their growth characteristics and resource use efficiency limit successful management of these crops. This research compares the response of different heritage and modern crop cultivars to irrigation, nitrogen (N) fertiliser and canopy management. Some heritage cultivars produced as much marketable yield as modern cultivars while other heritage cultivars had low yields. Modern potatoes were more responsive to irrigation and N than heritage potato crops (collectively known as Taewa). Application of more than 80 kg N ha-1 decreased yield in Taewa (Moe Moe, Tutaekuri) whereas, it increased the yield of modern potatoes (Agria, Moonlight). Full irrigation (FI) increased yield in modern potatoes and Moe Moe. In contrast, Tutaekuri yield was greatest with partial irrigation (PI). FI and 80 kg N ha-1 are recommended for Moe Moe production whereas PI and less than 80 kg N ha-1 are recommended for Tutaekuri. In addition, greater tuber dry matter and low sugar content suggest that Taewa would have better cooking and processing qualities than modern potatoes. Heritage crops required more water than modern crop cultivars because they mature later. There was high ‘water use efficiency’ in heritage pumpkin squash; high ‘irrigation water use efficiency’ in modern potatoes and high ‘economic water productivity’ for heritage potatoes and pumpkin squash. Heritage crop cultivars adapted to water deficit by developing more roots, higher photosynthetic WUE and leaf water potential than modern cultivars. Although total biomass production was similar, heritage crops tended to produce less marketable yield than modern cultivars because of excessive vegetative growth and potato psyllid infestation. Two strategies to manage the canopy and reduce vegetative growth using chlorocholine chloride (CCC) and mechanical topping were developed. Both strategies increased marketable yield in Taewa by 32 - 44%. Application of CCC at 25 and 50 days after emergence (DAE) was recommended for irrigated Taewa, whereas mechanical topping and application of CCC at 25 and 30 DAE were recommended for both irrigated and rain-fed Taewa. The study also observed that potato psyllid need to be controlled up to 170 DAE in Taewa to avoid yield loss equivalent to NZ$10, 485 to NZ$17, 412 per ha. This study contributes to policy on sustainable and improved Maori land use. It can be concluded that premium market prices are important to the success of heritage crops (i.e. to maintain their high ‘economic water productivity’) whereas modern crops might use irrigation water more efficiently (i.e. greater ‘water use efficiency’). It is evident that heritage crops can be grown successfully, and that on occasions they use valuable resources efficiently. To enhance water use efficiency, management of heritage crops should focus on improving the harvest index.
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    The lifecycle and epidemiology of the tomato/potato psyllid (Bactericera cockerelli) on three traditional Māori food sources : a thesis in partial fulfilment for the degree of Master of Science in Plant Protection at Massey University, Palmerston North, New Zealand
    (Massey University, 2011) Puketapu, Aleise
    The tomato/potato psyllid (Bactericera cockerelli (Sulc), TPP) is a species of Psylloidea first detected in New Zealand in 2006. Since its incursion the TPP has proved to be a major insect pest of solanaceous crops, particularly potatoes (Solanum tuberosum), tomatoes (Lycopersicon esculentum) and capsicums (Capsicum L.). The TPP is a vector of Zebra Chip Disease or liberibacter (Candidatus Liberibacter solanacearum syn. psyllaurous), a lethal plant disease related to Citrus greening disease (Candidatus Liberibacter asiaticus). Successive annual population outbreaks coupled with widespread liberibacter infection continues to challenge New Zealand‘s horticulture sector. Three traditional Maori food sources, namely taewa (Solanaceae, Solanum tuberosum L. ssp. andigena and ssp. tuberosum), kumara (Convolvulaceae, Ipomoea batatas (l.) Lam.) and poroporo (Solanaceae, Solanum aviculare G. Forst syn. S. Laciniatum (LINN.), are known to be susceptible to TPP infestation. Kumara and taewa are annual summer plants present during the peak TPP development and population growth period. Poroporo flowers and fruits year-round and is therefore theoretically susceptible to infestation throughout the year and may serve as a potential overwintering host and food source for TPP. Poroporo was assessed as an overwintering host of the TPP and the lifecycle progression of TPP was also compared on the three host plant species; taewa, kumara and poroporo. The role of these three host plants in the annual lifecycle of this insect pest in the New Zealand environment. The results showed that poroporo was not an important overwintering host of the TPP in the Manawatu/Rangitikei region; rather it can be viewed as an alternative or refuge host in the absence of the primary solanaceous host species and other volunteer weed host plants. The results indicated that taewa is a more suitable host of the TPP than poroporo and kumara. In the same vein, poroporo is clearly more suitable as a host than kumara. The relationship seen in this study in terms of host suitability can be pictorially represented as; Taewa> Poroporo> Kumara This study showed that all three host species are capable of supporting TPP and therefore each of the host species should be managed with a view to minimise the impact of TPP across seasons.