The keynote address discussed the opportunities biodiversity provides to humanity, challenges to its conservation and the essential role seeds will play in enabling the future use of this biodiversity.
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Management plans for the grazed parklands of the Auckland volcanic cones call for revegetation to restore a more natural and historic vegetation cover. The native grass Microlaena stipoides has been identified as a relevant species, and a field experiment was undertaken to determine the best approach for establishing this species into existing pasture. Seed obtained locally was broadcast or hydro-seeded in May 2007 onto kikuyu pasture, at three sowing rates (100, 250 and 750 seeds/m2) following control of the resident pasture with turf stripping or mowing and spraying, in a replicated factorial trial. After 12 months, the highest levels of Microlaena plant density (mean 56 plants/m2), cover (mean 50%) and accumulated herbage mass were observed on broadcast/sprayed plots at the highest sowing rate. Recovery of the resident pasture (dominantly Pennisetum clandestinum) occurred to a level of ~25% after 12 months, but was inhibited at the highest Microlaena sowing rate. Keywords: broadcast, hydro-seeding, kikuyu, Microlaena stipoides, re-vegetation
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(208 KB)A predator-proof fence enclosing 270 m2 of predominantly kauri (Agathis australis) bush on Limestone Downs was erected in February 2004. Regeneration of A. australis and other seed-dispersed species was monitored in permanent quadrats laid out within and immediately outside the enclosure. The quantity of viable A. australis seed entering the enclosure by natural dispersal and extent of viable A. australis seed within the soil seed bank were measured. Two thirds of the viable seed dispersed was lost, probably through mammalian predation. Eleven species were found in the soil seed bank. No viable A. australis seed was found in the soil seed bank. Seed rain was the source of viable A. australis seed. Regeneration of A. australis was greater within the protected environment of the predator-proof fence. There was a decline in seedling numbers between May 2007 and April 2008 both inside and outside the predator-proof fence suggesting that predation was not the only factor influencing seedling survival. Keywords: Agathis australis, Xcluder™ fence, seed predation, seedling survival, regeneration, seed rain
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(232 KB)At least one third of New Zealand’s indigenous plant species are threatened with extinction and strategies for conserving endangered flora are urgently required. One strategy is to use ex situ seed storage as a complement to in situ conservation. Successful ex situ storage of seed requires knowledge of the seed storage behaviour, optimal storage conditions and germination requirements of the species being stored. For many threatened species, however, this information is either incomplete or unavailable. In this study, preliminary experiments were conducted with three threatened species, Carmichaelia williamsii, Clianthus puniceus and Hibiscus diversifolius, to determine their desiccation tolerance and dormancy status. Seeds were tested for germination following desiccation and dormancy-breaking treatment. Seeds of all three species could be dried to moisture contents of 2.9-3.7% without losing viability. All three species became predominantly hardseeded at approximately 10% moisture content. However, C. puniceus became permeable to water again at moisture contents below 6%. In all species, manual scarification of seeds improved germination to 96-100% compared with 5-20% in untreated seeds. Dormancy in these species is a function of the seed coat preventing water uptake by the dry seed. While seeds of these species are most likely desiccation tolerant and thus can potentially be stored for long periods under conventional conditions, the loss of dormancy of C. puniceus at very low moisture contents is of concern. More work is needed to confirm the long-term storage behaviour of these species. Keywords: ex situ conservation, seed storage behaviour, New Zealand flora
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(267 KB)The New Zealand flora is a mixture of indigenous and introduced species. The indigenous species have a high intrinsic value while the introduced species include all of the crop and pasture plants upon which the export-led economy depends. New Zealand must maintain both of these important sources of biodiversity in balance. Seed banks are useful tools for biodiversity management. In New Zealand, a seed bank for indigenous species has been a very recent initiative. By contrast, seed banks for introduced species have been established for over 70 years. The reasons for this discrepancy are discussed. For the economic species, conserved genetic diversity is used to enhance productivity and the environment. Large advances can be gained from species that are not used as economic plants. The gene-pool of white clover has been expanded by the use of minor species conserved as seeds in the Margot Forde Germplasm Centre. Keywords: Seed banks, biodiversity conservation, New Zealand flora
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In cereals, the importance of the flag leaf for contributing carbohydrate during seed fill is well documented. However, in ryegrass this relationship is not so clear. This paper reports on an investigation of the effect on seed yield components of reduced photosynthetic capacity to the flag leaf, stem and head of perennial ryegrass (Lolium perenne). The hypothesis was that reduced photosynthetic capacity of the flag leaf does not affect seed yield components in perennial ryegrass. Following flowering, photosynthetic capacity was reduced by defoliation or shading the flag leaf, stem, or head of individual tillers. Seed yield components were measured at harvest. Reduced photosynthetically active radiation (PAR) to the flag leaf and stem did not affect thousand seed weight or seed yield when compared with control plants whereas reducing PAR to the head had a significant effect. The seed head itself may be more important than the flag leaf during seed fill, but when the seed head is shaded substantial re-mobilisation of stored carbohydrates can occur. Keywords: flag leaf, green leaf area, Lolium perenne, photosynthetically active radiation, seed fill, seed yield, thousand seed weight, water-soluble carbohydrates
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(187 KB)Seed pathology, which has at least a 120- year history in New Zealand, began with experiments for the control of cereal smuts. A brief history of seed pathology in New Zealand for the eras pre-1930, 1930-1960, 1960-1980, 1980-2000 is presented. New Zealand seed pathology has concentrated on diseases of the Poaceae and large-seeded legumes. Little is known of the occurrence or significance of seed-borne pathogens of other species, particularly vegetables. The New Zealand seed trade has for many years relied on fungicide seed treatment to control seed-borne pathogens of cereals, peas and brassicas, but currently there are problems with Fusarium spp. in cereals. New Zealand, as a biosecurity conscious nation, has strict measures in place to prevent the unwanted introduction of new plant pests. These requirements are briefly discussed. However seed health testing is carried out routinely only for seed lots requiring evidence of freedom from seed-borne pathogens for export phytosanitary requirements. In many cases knowledge of the health status of seed lots sown in New Zealand would enable better informed crop management decisions. Keywords: seed-borne diseases, seed pathology, seed health testing, seed treatment
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(174 KB)Industrial hemp (Cannabis sativa) is an ancient crop. The majority of hemp production has been for fibre, but more recently interest in the use of hemp seed oil has developed. The German-bred monoecious dual-purpose cultivar ‘Fasamo’ was trialled over two years in Canterbury to determine the optimum plant population for oilseed production. Target populations were 125, 150, 175, 200, 225 and 250 plants/m2. Actual established populations ranged from 124 to 346 plants/m2. In 2006-07, yields ranged from 804 kg/ha to 931 kg/ha, with a positive linear trend of 0.823 kg/ha yield gain for every extra plant/m2 established. Economic return ranged from $3,482 to $3,838/ha, with a non-significant positive linear trend of $2.44 nett gain for every extra plant/m2 established. In 2007-08 yields were much higher, ranging from 1,640 to 1,849 kg/ha producing an economic return of $7,183 to $8,092/ha. However, there was no significant linear trend found between established plant density and either yield or economic return. Oil quality did not appear to be affected by differing plant populations. Agronomic management and climatic conditions during production appeared to have a greater impact on yield and economic return than plant population. Considering both practical and quantitative factors, a target plant population of 150-225 plants/m2 is recommended for Fasamo oilseed production in Canterbury depending on site yield potential. Keywords: Cannabis sativa, oil content, plant population, economic return, essential fatty acids, α-linolenic acid, γ-linolenic acid, linoleic acid, oleic acid
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(188 KB)The introduction of the plant growth regulator trinexapac-ethyl (Moddus) has increased seed yields in perennial ryegrass (Lolium perenne) by up to 50% in New Zealand. Application rates from ten trials have confirmed that approximately 1.6 l/ha are optimum. Yield increases are a result of increased harvest index and better dry matter partitioning to the harvested parts. The resulting changes in harvest components include increasing seed head density and seeds per spikelet (better seed retention) associated with delayed lodging. Keywords: Lolium perenne, lodging, Moddus, seeds/spikelet, trinexapac-ethyl
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(262 KB)Results from 17 nitrogen (N) rate response trials using current best management including the plant growth regulator trinexapac-ethyl (Moddus) were used to predict optimum applied N rates for perennial ryegrass. The average optimum applied N rate was 145 kg/ha. A simple model using late winter soil mineral N (0-30 cm) and a total N requirement (mineral N + applied N) of 185 kg N/ha is recommended for growers to predict the applied spring N rate. Keywords: nitrogen, optimum rate, Lolium perenne, seed yield
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(200 KB)The New Zealand seed industry developed from an awareness over 100 years ago that standards were required for sale and purchase of seed. This paper outlines twelve decades of growth, covering seminal moments and major contributors. It also covers important components of physical seed quality.
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(159 KB)The hypothesis that by increasing carrot (Daucus carota) plant density the contribution to seed yield by the primary umbels would increase, and that therefore both seed yield and seed quality would increase, was examined in two experiments in different years in Canterbury. A radial trial design provided plant densities from 2 to 84 plants/m2 and from 4 to 100 plants/m2 in experiments one and two respectively. Seed yield increased with increasing plant density in both experiments, and at the highest density the primary umbels contributed 90% (experiment one) and 60% (experiment two) of the seed yield. In both experiments seeds from the primary umbels had a greater thousand seed weight and higher germination than those from the other order umbels, and for the second experiment they also had higher seed vigour. The quality of seeds from the primary umbels was consistently higher than that of seeds from the secondary umbels across all plant densities, and for the latter, both germination and seed vigour declined as plant density increased. These results therefore support the hypothesis, and densities higher than the 20 plants/m2 currently used commercially have the potential to increase both seed yield and quality. Keywords: seed production, primary umbels, germination, vigour, plants/m2
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Hydrothermal germination models are mathematical models which predict germination time of seeds for a specified seed-bed temperature (T) and water potential (Ψ). In this paper, the commonly observed decline in seed germination at supra-optimal temperatures is investigated by fitting a hydrothermal time model to germination data from two unrelated plant species (Buddleia davidii and Pinus radiata). For both these species, reduced germination rates and germination percentages above optimum temperatures (20°C and 25°C for P. radiata and B. davidii, respectively) were successfully modelled by an upward shift in the seeds’ base water potential (Ψb) during germination. The upwards shift in Ψb was shown to be an asymptotic function of time to germination, but with the rate increased by higher temperatures and moister seed-bed conditions. The physiological and ecological implications of this proposed model of the observed decline in germination at supraoptimal temperatures are discussed. Keywords: hydrothermal, model, Pinus radiata, Buddleia davidii
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(348 KB)Soil-borne damping-off diseases are a major constraint limiting pasture seedling emergence and yield. Large scale laboratory and glasshouse screening of beneficial micro-organisms against several host/pathogen systems was conducted to identify efficient bio-control and growthpromoting microbes. This was followed by field-testing of the best microbes and their formulations for efficient application techniques. The research identified a number of fungal (Trichoderma spp.) and bacterial (Paenibacillus spp.) isolates which suppressed damping-off diseases and promoted plant growth of various pasture species. Preliminary field-trials with granule and seed-coat formulations confirmed the glasshouse results. Intensive research trials with a mix of four T. atroviride isolates, providing growth promotion and disease control activity, led to the development of a prototype pasture seed additive product. Keywords: damping-off diseases, Paenibacillus spp., seed-coating, Trichoderma spp.
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(150 KB)Two New Caledonian plant species, one belonging to the Rhamnaceae, Alphitonia neocaledonica (AN) and one belonging to the Proteaceae, Grevillea exul var rubiginosa (GER) were investigated in order to characterise their seed chemistry.
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(171 KB)Cytokinins are hormones that regulate many developmental and physiological processes in plants.
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(142 KB)Linseed (Linum usitatissimum) is grown in New Zealand for both oil extraction and baking purposes. Two new brown linseed cultivars ‘Bilton’ and ‘Biltstar’, both of Dutch origin, were trialled in the Ashburton district in 2006-07 and 2007-08, to evaluate their suitability for seed and oil production. They were compared with the current industry standard cultivar ‘Hinu’ and the more recently released cultivar ‘Juliet’. There was a large range in yields among sites and seasons. When meaned across sites, cultivar yields ranged from 2,596 to 3,012 kg/ha. Bilton and Juliet produced significantly higher yields than Hinu, while Biltstar was intermediate. Thousand seed weight ranged from 5.76 g to 7.65 g with Biltstar producing the heaviest seed. There was a significant cultivar effect for both oil content and α-linolenic acid (ALA) content. Biltstar and Juliet produced the highest oil content (40.7% and 40.3% respectively). ALA levels were highest in Biltstar and Hinu (62.1% and 60.9% of total fatty acids respectively). There was no significant difference in oil yield (kg oil/ha) among cultivars. Four cultivars may have a place in Canterbury for oilseed production depending on end use and grower payment conditions. Keywords: Linum usitatissimum, flaxseed, seed yield, oil content, α-linolenic acid, thousand seed weight
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(190 KB)Cytokinins are intimately involved in plant growth and development and their concentration is known to change dramatically during early stages of seed development. We propose that the concentration of active cytokinin may be coordinately regulated by specific member(s) of the multi-gene families encoding biosynthesis (isopentenyl transferase, IPT), catabolism (cytokinin oxidase, CKX), and metabolism (zeatin glucosyltransferases (ZOG) and β-glucosidase (GLU)) genes. Our qRT-PCR data for 22 putative genes showed that the expression patterns of individual members of the Triticum aestivum (Ta)IPTs, TaCKXs, TaZOGs, and TaGLUs multi-gene families were tissue and development specific during seed and flag leaf development, with up to 90-fold changes in mRNA level. Key genes that may be involved in seed yield determination have been identified. Keywords: Wheat, flag leaf, cytokinin genes, quantitative expression, qRT-PCR
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(348 KB)Natural or harvest-induced senescence is a major determinant factor causing crop losses. The plant hormone ethylene is a strong inducer of senescence and decreasing the ethylene response can reduce senescence, albeit often with undesirable pleiotropic effects. We took advantage of ethylene-induced leaf senescence as a tool to screen for late senescence Arabidopsis mutants that still have a functional ethylenesignalling pathway. Sixteen Arabidopsis onset of leaf death (old) mutants were selected that stayed green after treatment with ethylene. While all the mutants responded to ethylene in a triple response assay, ten mutants responded to the treatment in the same way as the wild type. These ten mutants showed limited pleiotropic effects when grown under standard growth conditions but nine mutants flowered slightly later than the wild type. Genetic characterisation of a subset of the mutants identified several independent loci controlling the leaf senescence process. The approach resulted in the isolation of several stay-green mutants with a functional ethylene response pathway. The late senescence mutants show extended leaf longevity and further research may advance the field of pre- or post-harvest senescence technology. The results, moreover, suggest that there is a correlation between senescence and floral induction. Keywords: Senescence, Arabidopsis, ethylene, mutant, shelf life
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(380 KB)New Zealand produces approximately 5,500 tonnes of brassica seed per year, two thirds of which, valued at $13M, is exported. Black rot caused by Xanthomonas campestris pv. campestris is a common disease of brassicas, and while crop losses are not extensive in New Zealand, internationally total crop losses have been reported. Seeds are the primary source of inoculum and the ease with which this inoculum spreads means that even small traces can cause severe epidemics. Genetic resistance to black rot is a complex trait which makes breeding for resistance in brassicas challenging. The effectiveness of chemical and cultural practices is variable. Biological control with natural antagonistic microbes may provide a more effective means of controlling black rot and other pests and diseases, and create opportunities for increasing the export value of brassica seed. Current cultural practices and the potential for biological control for the management of black rot are reviewed. Keywords: biocontrol, Brassicaceae, crucifer
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(174 KB)Vegetable seed has been produced in New Zealand for over a century. In the late 1900s the potential for global trade was realised and Canterbury has become the major area of vegetable seed production in New Zealand. The main species involved are onion, baby leaf vegetables, sweet corn and brassica. Squash, capsicum, tomato, lettuce and telegraph cucumber are also important. This paper outlines the development of the vegetable seed industry in New Zealand and suggests that future requirements to meet increasing demand for high quality seed will be irrigation and mechanisation.
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