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Subject: search.filters.subject.300406 Crop and pasture improvement (incl. selection and breeding)

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Now showing 1 - 9 of 9
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    Functional complementarity in diverse pastures : an agroecological approach for pasture-based dairy systems in temperate climates : 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 Copyright holders of copyrighted images may use the Copyright Take Down Request button below to request their removal., 2024) Anchão Oliveira, Bia
    The diversification of plant species within intensively managed pastures has been proposed as a potential solution to address climatic-driven issues of pasture-based livestock production. In New Zealand, pasture-based dairy systems are mostly composed of Lolium perenne L. with a smaller proportion of Trifolium repens L. Bromus valdivianus Phil. and Dactylis glomerata L. are grass species which have attributes of interest for pasture-based dairy systems, such as great productivity, quality and persistence. Previous studies have shown that these four species present distinct functional traits, such as deep- or shallow-root system and cool- or warm-season activity, among others. This thesis hypothesises their distinct functional traits to be complementary to each other when these four species comprise a diverse pasture. The leaf regrowth stage, plant-based grazing management, is adopted as the defoliation criteria management. Three studies were developed in the thesis. The first study assessed and validated the hydraulic lift, a new functional trait occurring in the root system C3 grass species. The second study investigated agronomical parameters and ecological features of a diverse pasture comprising L. perenne, B. valdivianus, D. glomerata and T. repens. When grown as a diverse pasture, these four species presented complementary functional traits, including growth asynchrony (seasonal growth activity) and development synchrony (temporal overlapping of their individual optimal LS intervals). Therefore, termed during the thesis as a diverse pasture of complementary species (DPCS). In relation to binary pastures (one grass and one legume component), DPCS presented lowered seasonality of production, annual and seasonal overyielding and a decrease in the ingression of volunteer species. The third study investigated the suitability of DPCS for dairy animals by measuring their nutritional quality, grazing behaviour, and dietary preferences of dairy cows. The animals displayed no preference when offered binary and DPCS simultaneously. Overall, this thesis provides enough evidence to support the advising of diverse pastures comprising L. perenne, T. repens, B. valdivianus, and D. glomerata defoliated according to the leaf regrowth stage as an alternative for pasture-based dairy systems in temperate humid climates.
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    Value added wheat through applied genomic prediction : a genomic approach for breeding low gluten epitope wheat : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Breeding and Genetics at Massey University, Palmerston North, New Zealand. EMBARGOED until 24 July 2026.
    (Massey University, 2023) Macalister, Jamie
    Gluten epitopes are known to trigger coeliac disease (CD) in affected consumers and are believed to be linked to some cases of gluten intolerance. Research suggests that if consumers were exposed to wheat with reduced concentrations of gluten epitopes, the incidence of CD and gluten intolerance may be reduced. Methods have recently been developed allowing researchers to measure gluten epitope concentrations in wheat. This offers wheat breeders the potential to select towards varieties with lower epitope concentrations than existing cultivars. However, the methods for measuring epitope concentrations remain costly and time consuming. Therefore, it is proposed that a genomic based approach for breeding low epitope wheat lines is a more practical method than traditional phenotype-based selections. The genetic factors associated with epitope concentrations remain poorly understood. In this thesis, heritability estimates of between 0.37-0.93 are reported for concentrations of 6 distinct gluten epitopes. The associations between epitope concentrations and baking quality are also assessed and are shown to range from being near zero for some epitopes to strong positive correlations between other epitopes and particular baking quality characteristics. A Genome Wide Association Study and a model for genomic prediction are employed to determine the genetic factors associated with epitope concentrations. In these analyses, 3 significant genomic windows are identified as being associated with concentrations of 3 particular epitopes. Empirical prediction accuracies of between 0.16-0.53 are observed for predictions of epitope concentrations in a breeding population. Additionally, accuracies of between 0.37-0.67 are achieved by adjusting the population structure to represent the ideal circumstances that breeders would aim to achieve in their training and target populations. These results demonstrate that genomic selection (GS) will be an effective method for breeding low gluten epitope wheat. The outcome of this thesis will allow implementation of GS in the New Zealand Institute for Plant & Food Research wheat breeding program where epitope concentrations will be established as a new breeding target. This is expected to lead to the release of niche, low epitope cultivars with a value-add component that benefits growers, industry and consumers.
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    Phenotypic and genetic diversity in nitrate-responsive regulation of symbiotic nitrogen fixation in Medicago truncatula : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Plant Breeding at Massey University, Manawatū, New Zealand. EMBARGOED until 16th April 2026
    (Massey University, 2024) Dawson, Gregory Peter
    Finding alternatives to synthetic nitrogen fertilisers is important in order to reduce human fossil fuel use. An alternative method is biological nitrogen fixation by legume-rhizobia symbiosis, but the amount of nitrogen fixed by symbiosis is too small to fully replace use of synthetic fertilisers in high-productivity agricultural systems. Supplementing fertiliser is inefficient because symbiotic fixation is downregulated by plants when nitrogen fertilisers are present in the soil. In this study, several Medicago HapMap Project accessions are tested for sensitivity to nitrates. It was shown that nitrate in soil causes the plant host to regulate new infections by rhizobia and rhizobial nitrogen-fixing activity in a partially independent manner. Sensitivity to nitrates varied widely between accessions. Several accessions were identified with minimal inhibition of infections under nitrate conditions, and others were identified that show only moderate inhibition of symbiotic nitrogen fixation activity.--Shortened abstract
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    A study of the effects of plant spacing and irrigation on seed production and seed development in Siratro (Macroptilium atropurpureum) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Seed Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 1983) Juntakool, Sunanta
    Since 1980 the Thai government has been interested and active in increasing livestock production by improving the productivity and quality of natural and sown grassland. The introduction of forage legumes, particularly Siratro (Macroptilium atropurpureum), is one of the ways in which this can and is being achieved. The present study was carried out in two parts - the first involving two field trials conducted in Thailand during the wet and the dry season, and the second involving a controlled climate study at Palmerston North (N.Z.). The aim of the field trials was to investigate the effects of plant spacing, and during the dry season the effect of irrigation on Siratro seed production. In the controlled climate study a more detailed investigation was undertaken of the effects of water stress on plant growth and development and subsequent effects on seed yield. Particular attention was also given to relevant aspects of seed development in the latter study. Irrigation during the dry season produced relatively small but significant increases in plant dry weight and LAI and led to a sig­nificant increase in seed yield by the final harvest 40 days after peak flowering. By comparison, plant spacing had a marked effect on plant components and seed yield showing a negative response on a per plant basis but a positive response on a per unit area basis with increasing plant density. During the longer growing period of the wet season experiment, plant growth was substantial and again showed the same significant responses to increasing plant density stated above. Maximum seed yield per hectare was achieved at very high plant population densities approxi­mately 15 x 15 cm spacings. The major contributions to seed yield in both trials were inflores­cence numbers and especially pod numbers, reflecting their sensitivity to water stress and plant competition. Numbers of seeds per pod and individual seed weight were relatively insensitive to those environ­ mental factors. The growth room study clearly showed that early and extended soil moisture stress can cause a severe reduction in plant weight, branch development, leaf number and LAI, leading to a significant reduction in seed yield. However, soil moisture stress imposed at peak flower­ing resulted in a significant increase in seed yield compared with adequate moisture to final harvest. This beneficial effect was again due mainly to the increase in the number of inflorescences and pods formed on the primary and particularly the secondary branches. Numbers of seeds per pod and individual seed weight were again un­affected by water stress. The development of Siratro seed followed two obvious phases viz the growth and food reserve.accumulation phase and the ripening phase. Water stress reduced the time from anthesis to seed maturity and increased the percentage of hard seed at harvest when imposed early at the mid- vegetative stage. Plant spacing and irrigation had little or no effect on seed quality characteristics of Siratro, as quality appeared to be more dependent on stage of maturity. High seed quality can be achieved by harvesting Siratro 20 - 30 days after peak flowering. The possibility of growing Siratro for seed production in Thailand is also discussed.
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    Assessing provenances of Moringa oleifera L. for salt tolerance and low methane emission : a thesis presented in the partial fulfilment of the requirements for the degree of Master of Science in Plant Breeding at Massey University, Palmerston North, New Zealand
    (Massey University, 2022) Mangar, Adrian
    Moringa oleifera has a high nutritional content and easy propagation. It is well known worldwide where it grows best in tropical and sub- tropical environments. M. oleifera originated from Northern India, but plants can be found growing in Guyana, South America, where most of the agricultural lands are on the coastal plains and sea water intrusion is common. The objective of this study was to carry out a pre-breeding characterization of six M. oleifera provenances, four from Guyana and two from India for salt tolerance and their effect on rumen methane emissions compared with high quality pasture species. A salt tolerance trial using the six provenances was done in a greenhouse at the Massey Plant Growth Unit, Batchelar Road, Palmerston North. The experiment was set up in a randomised complete block design, containing five blocks and three levels of salinity (0 mM, 52 mM and 156 mM NaCl). For each treatment ten seeds were sown in two pots and the salt treatments were applied by immersing pots for 30 minutes in the respective salt solutions every seven days for 21 days. Plant growth and net photosynthesis were measured during the stress period, chlorophyll content measured before and after salt stress, and biomass measurements along with sodium concentration in leaves, were taken at the end of the experiment. Methane and total gas production were measured using an in vitro batch culture system. Two experiments were done, a preliminary screening using oven dried M. oleifera planted in field and greenhouse, and a main experiment using the six provenances, a composite sample and M. oleifera leaves from greenhouse. Both experiments compared the different M. oleifera sources with high quality ryegrass and white clover. Real time gas production was recorded for 48 hours, total gas production, methane analysed at 12 and 24h. Short chain fatty acids concentration were also determined at the end of the fermentation. The preliminary experiment showed that M. oleifera leaves grown in field and greenhouse have lower gas and methane production compared with ryegrass, but similar to white clover. The differences were driven by a high production of propionic and butyric acids. The six M. oleifera provenances also produced less methane than ryegrass but similar to white clover at 12 and 24 hours after the start of fermentation. Salinity screening of the six M. oleifera provenances showed a significant (P < 0.001) reduction in plant growth at 156 mM NaCl. There was an increase in sodium in photosynthetic active leaves as salt stress increased. However, at 52 mM NaCl plants survived and showed no significant difference in root and above ground plant biomass when compared with the control. Net Photosynthesis was also not significantly affected by the application of 52 mM NaCl salt stress and there was also no significant reduction of plant percent dry weight at 52 mM NaCl when compared with control plants. Future work should include screening of more M. oleifera provenances for salinity tolerance and determination of the genetic diversity among these provenances. This would help determine the origin of the seeds sourced from King Seeds (Katikati, New Zealand) and their relation to the seeds sourced from Guyana and India. Cold tolerance screening should also be carried out using provenances from Northern India, which will help widen the gene pool for the creation of a base population for breeding programmes.
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    Plantain mixed pasture : seasonality of herbage accumulation and potential for mitigating nitrous oxide emissions from cow urine patches : a thesis presented in partial fulfilment of the requirements for the degree of Master in Horticulture Science at Massey University, Manawatū, New Zealand
    (Massey University, 2021) Vi, Kim Chi
    There is growing evidence that plantain (Plantago lanceolata L.) is recognised by dairy farmers to improve summer feed productivity and quality and to mitigate nitrogen (N) pollution from grazed pastoral soils. However, there is still limited information on the proportion of plantain required when it is mixed with perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) pasture to optimise its yield stability and environmental benefits. The objectives of this thesis were to monitor seasonal changes in the contribution of plantain to perennial ryegrass/white clover pastures, and to evaluate the effect of incorporating plantain in the pasture diet of dairy cows on nitrous oxide (N₂O) emissions from urine patches during summer and autumn. The field experiment was conducted over two growing seasons (2019/2020 and 2020/2021). The research site consisted of 20 experimental plots: each plot was 800 m² (20 m x 40m). There were four treatments, with different proportions of plantain (0%, 30%, 50% and 70%) in ryegrass/white clover pastures. Each treatment was replicated five times. The proportion of plantain in the mixed pasture treatments reached a peak of 40% in the first growing season and of 50% in the second growing season during summer- autumn period. At the end of the first growing season following establishment of the treatments, the plantain proportion in the 50% and 70% plantain mixed pasture treatments were similar as around 50%. Plant density of plantain increased by 35% over the first growing season, but it decreased by 52–62% during the second growing season. Overall, the 30% and 50% plantain mixed pastures maintained more stable proportions of plantain than the 70% plantain mixed pasture treatment. Including 30% and 50% plantain in the summer/autumn grazed diet of dairy cows reduced the urinary-N concentration to 5.40 and 4.40g N L⁻¹, respectively, compared to 6.15g N L⁻¹ in urine from cows fed ryegrass and white clover. A lower N content in urine from cows grazing 50% plantain mixed pasture produced 39% less total N₂O emissions compared to ryegrass/white clover urine treatment, regardless of plantain treatments. Total N2O emissions and the emission factor (EF₃) for plantain mixed pastures were 16% and 27%, respectively, lower than for ryegrass/white clover pasture. The effect of plantain swards on decreased N₂O emissions was linked to changes in soil N-cycling and water-filled pore space values. Plantain proportions of 30% to 50% in mixed pastures were relatively stable over two growing seasons and reduced the urinary-N concentration resulting in the subsequently decreased in N₂O emissions from urine patches in summer/ autumn season.
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    Leaf regrowth stage as a morpho-physiological indicator of Bromus valdivianus and Lolium perenne mixed pasture defoliation in New Zealand grazing system : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, Manawatū, New Zealand
    (Massey University, 2022) García Favre, Javier Horacio
    Bromus valdivianus Phill. is a perennial grass species native to the South of Chile. Its better fitness for growing under low water availabilities compared with Lolium perenne L. has been assessed in field and glasshouse studies. However, Bromus valdivianus morpho-physiological attributes, such as root development under field conditions, and competitive ability are likely to manifest differently under contrasting defoliation criteria based on leaf regrowth stage. In addition, Lolium perenne and B. valdivianus growth can be complementary throughout the year under rainfed conditions. Therefore, the objective of the present thesis was to determine defoliation criteria based on leaf regrowth stage of mixed pastures (50/50% L. perenne and B. valdivianus) and consequences for species succession and functional traits development of the species. Four studies were developed in the thesis, two glasshouse and two field studies. The first glasshouse study evaluated the growth response and water-soluble carbohydrate (WSC) accumulation of B. valdivianus at three different defoliation frequencies. The results suggested that B. valdivianus increased herbage mass production and root biomass at low defoliation frequency (i.e., at 3.5–4.0 leaf regrowth stage). This was related to a higher WSC accumulation in the tiller base. In addition, under low soil water availabilities (20–25% of field capacity) WSC increased by ~20%, which indicated a drought resistant strategy of this species. The second study proved the growth enhancement (mainly root length and biomass) of B. valdivianus under competition with L. perenne compared with intraspecific competition when soil water shifted from high to low availabilities. In field studies, B. valdivianus mixed with L. perenne increased ~15% accumulated herbage mass compared to the species monocultures, which supported higher production during dry periods. This was due to the niche complementarity and asynchrony in herbage growth between the species, with B. valdivianus capable to maintain a steady tiller population throughout the year and root biomass accumulation at depth. Whereas L. perenne grew more than B. valdivianus under low level of oxygen in the soil and under optimal growth conditions and presented a higher nutritive value than B. valdivianus during winter, spring and autumn. The latter supports the partial grazing preference for L. perenne shown by sheep during part of the year, as measured in the second field study. This lower nutritive value (less energy) of B. valdivianus monocultures was overcame in the mixture, with a good overall value for high animal production. Regarding the mixture defoliation criterion, it was shown that it can be based on the optimal leaf regrowth stage of either species, as herbage mass production was similar between defoliation frequencies based on optimal leaf regrowth stage of either of the species. However, under defoliation based on optimal leaf regrowth stage of B. valdivianus, root biomass accumulation at depth increased ~45%. Overall, the results of the present thesis evidenced that Bromus valdivianus can successfully grow alongside L. perenne and, therefore, the mixture can increase forage production of New Zealand farming system in the event of climate change.
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    Genetic signatures in a perennial ryegrass (Lolium perenne) population following recurrent selection for compatibility with an endophyte (Epichloë spp.) from tall fescue : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Plant Breeding at Massey University, Palmerston North, New Zealand
    (Massey University, 2019) Pocsedio, Arnel E.
    Perennial ryegrass or Lolium perenne L. (Poaceae) is the most extensively grown forage especially in the temperate regions of the world, including New Zealand. The development of forage cultivars is important to New Zealand since the livestock industry depends on perennial ryegrass for its nutrition needs. Among forage breeding objectives, persistence is particularly complex. It refers to the stability of dry matter yield over time. It is economically important because reseeding and cultivation can be capital-intensive. Persistence is partly modulated by the interaction of perennial ryegrass with Epichloë spp. as these fungal endophytes confer insect resistance for a more stable yield. Genetic factors in the host influence fungal biomass, alkaloid concentration, and endophyte vertical transmission frequency. The symbiotic relationship is therefore exploited in perennial ryegrass breeding. Thus, the objective of this study is to investigate a perennial ryegrass breeding population under recurrent selection (RS) for compatibility with an endophyte sourced from tall fescue. Specifically, this study aims to (1) investigate the transmission of the Epichloë sp. FaTG-3 strain AR501 in the breeding population PGG04, and (2) to examine how genetic variation changes during RS in terms of population differentiation. Since the selection program targets endophyte compatibility, signatures of selection that may be associated with the grass-endophyte interaction were also determined. It was hypothesized that: there will be a reduction of diversity, and an excess of rare alleles. Furthermore, it was hypothesized that loci under positive selection will have higher fixation index (FST), and their genotypes will be more correlated with the components of PCA- based population structure analysis compared to neutral loci. The presence of AR501 was examined in seeds, in the growing tillers, and by microsatellite genotyping for both the early and late generations of PGG04. The seed squash assay revealed that more than 90% of PGG04 seeds harboured the endophyte, regardless of the generation. Viable endophyte detection using tissue-print immunoblotting showed an increase in infection from ca. 5% to 33% between the early and late generations. Thus, the results suggest that positive selection for endophyte compatibility increased the proportion of viable endophyte in the population. This study provides evidence supporting host genetic control of the association in grass-endophyte interaction, and that this can be exploited in plant breeding programs. Changes in the genetic variation of PGG04 was investigated by comparing GBS data of the early and late generations. Results showed that selection enriched the late generation with rare alleles (0.02 - 0.08) compared with the early generation. Also, selection reduced expected heterozygosity from 0.3069 in PGG04-C2 to 0.3033 in PGG04-C6. Further, selection changed the population structure based on UPGMA dendrogram, PCA, and the model-based clustering method implemented in STRUCTURE. A few single nucleotide polymorphisms (SNPs) have relatively larger contribution to the population structure changes hence, they have relatively high FST, and their genotypes correlated with principal components. Logistic regression of these SNPs with infection data identified nine SNPs to be associated with the trait. Depending on the allele frequency, these SNPs can increase the odds of favourable infection by more than five times. Annotation of these SNPs identified S7_160751877 to be tagging an ABCG transporter gene. Since some ABC transporters mediate plant-microbe interactions, it is possible that the identified SNPs are tagging a gene involved in the host genetic control of grass-endophyte interaction.
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    Assessing the potential of genomic selection to improve yield and persistence in white clover : a thesis presented in the partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Plant Biology at Massey University, Manawatu, New Zealand
    (Massey University, 2020) Ehoche, Oiwodu Grace
    White clover (Trifolium repens L.) is an economically important forage legume in temperate pastures, providing quality fodder and plant-available nitrogen. However, its potential has not been fully exploited due to unpredictable herbage yield and poor vegetative persistence in pasture. Identification of genotypes that combine traits essential for yield and vegetative persistence, like dry matter yield and stolon density, are key objectives in breeding programmes. Long breeding cycles, high genome complexity and difficult-to-phenotype traits, usually assessed at late growth stages, are major constraints to conventional phenotypic selection in white clover breeding. In cultivar development programmes, elite individuals must be accurately identified and selected before crossing to generate superior progeny. Genomic selection is becoming a preferred method for increasing the rate of genetic gain by enabling early identification and selection of superior individuals, based on their genomic estimated breeding values (GEBVs), which can be generated without the need for phenotyping. Genomic selection is usually performed using a statistical model developed using genotypic and phenotypic information derived from a training population. In forage breeding, as parental breeding values are estimated by progeny testing, phenotypic data used in genomic prediction models is obtained from half-sib progeny. Recent single nucleotide polymorphism (SNP) genotyping methods like genotyping by sequencing (GBS) which generate a large volume of SNP marker information at low cost, have made genomic selection possible for species such as white clover. The main objective of this thesis was to explore the potential of genomic selection to improve important traits in white clover breeding. Our results indicate, for the first time, an integrated phenotypic and genomic selection approach to be superior to conventional phenotypic selection at increasing genetic gain for a simple trait in white clover. This demonstrates the potential of genomic selection to be used in enhancing white clover breeding programmes for quantitative trait improvement.--Shortened abstract