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The importance of European honey bees in improving fruit set, yield and fruit weight of kiwifruit on the central east coast of Australia was investigated. Field investigations were carried out using different bee saturations and different types of male pollen parents. These investigations confirmed the importance of honey bees in kiwifruit fruit set, yield and fruit weight. However, the results suggested that increasing bee activity alone may not increase pollination of kiwifruit by honey bees. Many factors need to be understood before introducing bees into the orchard. Bees were more effective during the early part of the flowering period, and bee activity varied according to the sex of the vine, planting design and the time of day. The type of male pollen parents also influenced fruit size and quality. Flowers pollinated by different pollen parents were assessed for pollen tube growth and histochemical changes. The resulting fruit were also examined for weight and seed numbers. Honey bees play the major role in the size and yield of kiwifruit, but the design of male vines, their age and type of male pollen may also contribute. The kiwifruit pistil also possesses important features that can be considered as adaptations to insect pollination. / Doctor of Philosophy (PhD)

Memoria para optar al Título Profesional de Ingeniero Agrónom o Mención: Fruticultura

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Kiwifruit are of huge economic importance for New Zealand representing 29 percent of total horticultural exports. Fruit size is the biggest determinant of what consumers are willing to pay, and there is also a positive relationship between consumer preference for flavour and percentage dry matter. The two main cultivars exported from New Zealand are Actinidia chinensis ‘Hort 16A’ (gold kiwifruit) and A. deliciosa ‘Hayward’ (green kiwifruit). Under current commercial practice the only product allowed for use on kiwifruit to increase fruit size in New Zealand is Benefit®. Benefit® has been shown to induce different results when applied to A. chinensis and A. deliciosa, whereas synthetic plant growth regulators such as the cytokinin-like substance N-(2- chloro-4-pyridyl)-N’-phenylurea (CPPU) have been found to promote similar increases in fresh weight of fruit in both cultivars. Final fruit size is determined by both cell division and cell enlargement. It was been shown that fresh weight can be increased in both of the major Actinidia cultivars even though their physiology differs. Hormonal control of fruit size in relation to cell division and cell enlargement phases of fruit growth was studied in both A. chinensis and A. deliciosa. CPPU was applied to both cultivars in a growth response experiment where fruit were collected throughout the growing season. The objective of this experiment was to create growth curves, to compare and contrast the effect on A. chinensis and A. deliciosa, and to provide material for hormone analysis. Application of CPPU was found to significantly increase the fresh weight of both A. chinensis and A. deliciosa fruit (46.98 and 31.34 g increases respectively), and alter the ratio of inner and outer pericarps of A. chinensis fruit. CPPU and Benefit® were applied individually and together to both cultivars. It was found that only A. chinesis fruit were affected by the application of Benefit®; fresh weight was increased by 26.38 g, and percentage dry matter was significantly reduced. There was a statistically significant (p < 0.05) interaction between CPPU and Benefit® when applied to A. chinensis. 3,5,6-trichloro-2-pyridyloxyacetic acid (3,5,6-TPA) was applied to A. deliciosa on two application dates at three concentrations and was found to decrease fresh weight of fruit, but significantly increase percentage dry matter regardless of application date or concentration. Lastly CPPU and 1-naphthalene acetic acid (NAA) were applied to A. deliciosa at two application dates and in all combinations. Application date affected the response to both a low concentration of CPPU and NAA. A synergistic interaction was observed when CPPU was applied early plus NAA late (CPPU early (4.53 g increase) plus NAA late (13.29 g) < CPPU early plus NAA late (33.85 g). Finally endogenous hormone content was studied. Methods were developed and tested for the simultaneous analysis of both indole-3-acetic acid (IAA) and cytokinins. Freeze dried fruit were purified using Waters Sep-pak® cartridges and Oasis® columns then IAA was quantified by high pressure liquid chromatography. Preliminary results indicate a correlation between application of CPPU and endogenous IAA, high concentrations of IAA correlated well with periods of rapid fruit growth particularly for CPPU treated fruit.