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    Plant germplasm diversification strategies : a case study using Limonium : a thesis 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, 2024) Cordoba-Sanchez, Juana
    Limonium Mill. was chosen for this research as it has an established market for ornamental use and faces significant challenges in breeding including access to germplasm with traits of interest, self-incompatibility in most species, and pollen/stigma dimorphism which limits the types of cross combinations that can be performed. In interspecific crosses, challenges can be the low hybridisation rate (<1%), and the sterility/low fertility of interspecific hybrids. To address these challenges, increase the germplasm diversity available, and speed the development of cultivars, two breeding strategies were evaluated in this research: ploidy manipulation and physically induced mutations. The main outcomes were: 1. Efficacy of those strategies in: • Increasing the ploidy levels of the selected genotypes and therefore the germplasm diversity for The New Zealand Institute for Plant & Food Research Ltd (PFR)’s germplasm bank. • Increasing the hybridisation rate in interspecific crosses. • Fertility restoration in interspecific hybrids 2. Development of plants with new characteristics or different ploidy levels (i.e., triploids, tetraploids, or even higher ploidy levels). 3. Breeding protocols for Limonium using N2O which could be further used in other plant breeding programmes. The use of Limonium for the development of a new breeding strategies for increasing genetic diversity has a direct impact on other breeding programmes i.e., food crops. In addition, the Limonium industry could have access to continued novelty, ensuring industry access to new cultivars would benefit New Zealand’s economy mainly through royalties.
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    Limonium hybrid production and post-pollination biology : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Botany at Massey University
    (Massey University, 1995) Watson, Ian N
    The aim of this thesis is to determine barriers to interspecific hybridisation in selected Limonium species. Production of new commercially viable hybrids is essential to the development of the Limonium cut flower market. Very few studies have been published with respect to pollination and post-pollination biology of this genus so this study contributes a better understanding of events leading to fertilization and some of the factors involved in interspecific hybrid production. The thesis initially introduces the genus and its cultivation. Later chapters involve aspects of post-pollination biology and determination of normal development associated with fertilization, including pollen tube growth, ovary and ovule growth and embryo production. This information is used to judge the success, barriers and problem associated with new hybrid Limonium production. Interspecific hybrids were not obtained, but the information provided serves to highlight difficulties in hybrid production and provides opportunities for more directed breeding programmes.
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    Exploration of Limonium interspecific breeding possibility : a thesis presented in partial fulfilment of the requirement for the degree of Master of Science in Plant Science at Massey University, Palmerston North, New Zealand
    (Massey University, 1995) Zhang, Celia
    Interspecific crossability was investigated in the genus Limonium (Plumbaginaceae). Six Limonium species were chosen for this study, five of which are dimorphic and L.perigrinum which is monomorphic. Ovary, ovule and embryo development was investigated, as were in vitro pollen germination and pollen tube growth. Unilateral incompatibility was observed in 8 interspecific combinations. A high frequency of interspecific crossability was observed between L.perezii X L.sinuatum and L.sinense X L.aureum. Pollen tubes were frequently observed penetrating the ovules in these crosses. Pollen tube growth that terminated in the styles or was restricted to the stigmas was found in some Limonium interspecific crosses. Abnormalities of pollen tube growth in the interspecific crosses included heavy callose deposits at the tips of pollen tubes; pollen tube branching and pollen tube growing in the wrong direction. Embryo, ovule and ovary development was studied with L.perezii plants following conspecific pollination. Three distinct groupings of florets can be recognised at the basis of their post-pollination growth and development. Twenty-six percent of conspecific pollinated florets showed no ovary and ovule growth. No embryo was found in this group. In eleven percent of florets, ovaries and ovules grew up to Day 12 after pollination and then shrivelled. No embryo was ever found in this group. Sixty-three percent florets produced embryos following conspecific pollination and developed normally. The viability of Limonium pollen was assessed with Alexander's stain and fluorochromatic reaction (FCR) stain. Optimal conditions for in vitro L.perezii pollen germination and tube growth were established. Poly-ethylene glycol and filter paper supports were of particular significance. In vitro pollen germination rate of about 40% was achieved. Plant growth regulators (IAA, GA 3 and ethylene), some minerals (manganese sulphate, copper sulphate) and prehydration treatment were used in experiments to improve pollen germination and tube growth. None of these factors, however, had positive effect on either pollen germination or tube growth. It was found that while L.perezii pollen tube growth tolerates a wide range of temperature, there is an optimum between 20°C-25°C.