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    Segregation of ‘Hayward’ kiwifruit for storage potential using Vis-NIR spectroscopy
    (Elsevier BV, 2022-07) Li M; Pullanagari R; Yule I; East A
    Kiwifruit are often harvested unripe and kept in local coolstores for extended periods of time before being marketed. Many pre-harvest factors contribute to variation in fruit quality at harvest and during coolstorage, resulting in the difficulty in segregating fruit for their storage potential. The ability to forecast storage potential, both within and between populations of fruit, could enable segregation systems to be implemented at harvest to assist with inventory decision making and improve profitability. Visible-near infrared (Vis-NIR) spectroscopy is one of the most commonly used non-destructive techniques for estimation of internal quality of kiwifruit. Whilst many previous attempts focused on instantaneous quantification of quality attributes, the objective of this work was to investigate the use of Vis-NIR spectroscopy utilised at harvest to qualitatively forecast storage potential of individual or batches of kiwifruit. Commercially sourced ‘Hayward’ kiwifruit capturing large variability of storability were measured non-destructively at harvest using Vis-NIR spectrometer, and then assessed at 75, 100, 125 and 150 days after coolstorage at 0 °C. Machine learning classification models were developed using at-harvest Vis-NIR spectral data, to segregate storability of kiwifruit into two groups based on the export FF criterion of 9.8 N. The best prediction was obtained for fruit stored at 0 °C for 125 days: approximately 54% of the soft fruit (short storability) and 79% of the good fruit (long storability) could be predicted. Further novelty of this work lies within an independent external validation using data collected from a new season. Kiwifruit were repacked at harvest based on their potential storability predicted by the developed model, with the actual post-storage performance of the same fruit assessed to evaluate model robustness. Segregation between grower lines at harvest achieved 30% reduction in soft fruit after storage. Should the model be applied in the industry to enable sequential marketing, significant costs could be saved because of reduced fruit loss, repacking and condition checking costs.
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    Epidemiology and management of Sclerotinia sclerotiorum (Lib.) de Bary in kiwifruit (Actinidia deliciosa (A. Chev.)) : this thesis is presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2001) Hoyte, Stephen
    Kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson, var. deliciosa cv. „Hayward?), a valuable fruit grown in New Zealand orchards for export, is susceptible to the necrotrophic and cosmopolitan fungus Sclerotinia sclerotiorum (Lib.) de Bary. Sclerotinia disease causes direct crop loss in the form of diseased fruitlets, scarring of fruit and field rot of fruit. Costs to the industry amounting to an estimated $5 million pa. are incurred through crop loss on vines or during grading and through the purchase and application of fungicide. This study showed that 19% (range 0–53%) of 3–4 day-old kiwifruit petals were colonised by S. sclerotiorum ascospores arising from apothecia that were present within most orchards. Adhering floral tissues (AFT) were present on 38% of fruit 7–8 weeks after anthesis and 11% (range 0–43%) of these were colonised by S. sclerotiorum. The incidence of fruit with scarring was significantly higher on fruit with AFT than fruit without AFT. Removal of AFT 10–14 days after anthesis resulted in a 66% reduction in diseased fruitlets and a 85% reduction in fruit with scarring. Adhering floral tissues on fruit were therefore determined to be a major source of secondary spread. An in vitro assay was developed in which freshly detached kiwifruit petals were inoculated with dry S. sclerotiorum ascospores in a settling chamber and incubated for 72 h. The number of discrete colonies which formed on selective agar medium, when macerated petal tissue was spread on the agar, effectively quantified petal colonisation. Colonisation of petals significantly increased with increasing flower age. Colonisation of petals incubated under static conditions within saturated salt chambers was highest between 18–27oC and 90–100% relative humidity. Colonisation of petals in dynamically controlled environment chambers was inhibited by incubation in diurnally fluctuating temperature and relative humidity conditions typical of days with <5 mm rainfall during flowering. The minimum, maximum and optimum temperatures for mycelial growth on PDA and percentage germination of ascospores on water agar (5oC, 34oC and 23oC respectively) were similar to those for the rate of colonisation of petals by ascospores at 100% RH. Symptoms of diseased fruitlets, fruit scarring and field rot were reproduced in field inoculation experiments, provided free moisture was present for at least 9 h. Sclerotia iii were extracted from diseased fruitlets and fruit with field rot from three vines, yielding 2.7 and 18.6 sclerotia per unit respectively. Diseased fruitlets produced significantly smaller sclerotia, which had a higher germination rate and produced smaller apothecia, compared with sclerotia from fruit with field rot. External damage on 39% of sclerotia from fruit with field rot and their closer contact with soil micro-organisms during formation and maturation are likely causes for these observed differences in germination rate. Thus, the type of symptom which develops on pistillate vines can affect the potential for ascospore production during subsequent seasons through the production of ecologically distinct populations of sclerotia. During field studies in 18 orchards, positive relationships were shown between primary inoculum source (apothecial density) and primary infection (incidence of petal colonisation) and between both these factors and the incidence of diseased fruitlets and fruit with scarring. A conceptual model of inoculum production and disease development was constructed. This model highlights the importance of primary colonisation of floral tissues and showed that disease risk can be estimated from the apothecial density or the colonisation of petals by S. sclerotiorum. Model structures have also been developed for predicting disease risk and disease incidence. Disease management strategies are discussed, and if implemented, would rationalise decision processes and potentially reduce the costs of controlling sclerotinia. Decision support software could be developed to incorporate such models once they are validated and combined with further research to determine effective control measures. This software could then be integrated into a sclerotinia management system for kiwifruit in New Zealand.
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    Prediction of storage potential and firmness loss of 'Hayward' kiwifruit along the supply chains in India : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Albany campus, New Zealand
    (Massey University, 2012) Bellavi Jayashiva, Sneha Prakash
    The ‘Hayward’ kiwifruit (Actinidia deliciosa, C.F. Liang and A.R. Ferguson) is one of the most common commercial varieties grown in New Zealand. The long shelf-life of the ‘Hayward’ kiwifruit along with its inherent properties such as flavour, colour, texture and high content of vitamin C has allowed the development of New Zealand kiwifruit exports. However, the quality of the fruit can be affected by factors such as storage time and temperature along the supply chains to different markets. This study investigated changes in physiochemical parameters of kiwifruit along three supply chains to Indian markets, as well as development of predictive mathematical models for the loss of flesh firmness and storage potential of ‘Hayward’ kiwifruit along the supply chains. At each analysis point along the three supply chains, the ‘On arrival’ and ‘At departure’ quality of twenty kiwifruit were analysed for flesh firmness (kgf), soluble solids content (% Brix) and core temperatures (°C). The variation in the environmental temperature during storage and transportation along the supply chains were recorded. Three firmness loss models: Simple Exponential, Boltzmann and Inverse Exponential Polynomial were used to characterise the flesh firmness data collected along each supply chain. Three storage potential models: Reciprocal, Power and Reciprocal Quadratic, were fitted to the flesh firmness and core temperature data collected along each supply chain. The Akaike Information Criteria (AIC) test was used to determine the most suitable model that characterised the flesh firmness loss along the supply chains. The flesh firmness decreased (P<0.05) in all the grower lines along the three supply chains, while the soluble solids content increased (P<0.05) with temperature variation during storage and transportation. The Simple Exponential model best characterised the firmness data collected along supply chains 1 and 3. Changes in flesh firmness of fruit along supply chain 2 were best characterised by the Boltzmann model. The Reciprocal model best fitted the data on flesh firmness and core temperature. The Power model was the second best storage potential model that characterised the data collected along the three supply chains. The developed storage potential models may be used to determine the shelf-life of kiwifruit along similar supply chains in other markets.
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    Preharvest practices affecting postharvest quality of 'Hayward' kiwifruit : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Physiology and Horticultural Science at Massey University, New Zealand
    (Massey University, 2005) Buxton, Katrina Norah
    Repeat purchase of kiwifruit is primarily driven by consumer judgement of internal fruit quality attributes, including those affected by dry matter concentration (DMC) and mineral composition in fruit. This research investigated mechanisms affecting carbohydrate, mineral and water accumulation in 'Hayward' kiwifruit (Actinidia deliciosa), and related these to specific management practices. Canopy manipulation through pruning and treatments such as artificial pollination, defoliation, girdling, thinning and application of the auxin transport inhibitor TIBA, may affect fruit DMC and mineral composition. Leaf photosynthesis and fruit dry matter concentrations (DMC) started to decline as leaf area index values increased above 3-4. In addition to reducing competition for carbohydrates between vegetative and reproductive growth, leader pruning probably increased DMCs of fruit in the leader zone by improving light interception. Photosynthesis was not affected by crop loads between 20- 60 fruit m-2, but was consistently higher on non-terminating (long) shoots than on terminating (short) shoots, as were fruit DMCs. Differences in photosynthetic rate of leaves on these two shoot types were attributed to differences in shoot exposure to the sun, and also to the greater demand for carbohydrate within long shoots. Leaves subtending fruit may increase Ca, and to a lesser extent Mg, flow into fruit, however their accumulation was not affected by leaves outside the fruiting shoot. Xylem sap Ca and Mg concentrations were higher in shoots with a high rather than a low leaf: fruit (L:F) ratio and this may, at least partially, relate to the increase in shoot transpiration that occurs as shoot L:F ratios increase. Within vine variation in fruit Ca concentrations may reflect variations in xylem sap flow rates and Ca concentrations of xylem sap reaching fruit. Calcium translocation may occur independently of ion movement in the transpiration stream. Timing and extent of vascular differentiation in flower and fruitlet pedicels, possibly regulated by auxin, may influence fruit Ca accumulation. It is likely that early differentiation of vascular tissue in flower and fruitlet pedicels influenced cell division and subsequent (carbohydrate) sink strength of fruit by determining availability of carbohydrate for partitioning into cell walls. While growers have the potential to induce minor changes in fruit DMC, further increases will depend on the separation of carbohydrate and water accumulation. Further research is required to elucidate the mechanisms regulating phloem transport and unloading of sucrose in kiwifruit.