School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemInvestigations into rhizoctonia root rot resistance in aegilops tauschii and other wild wheat relatives(University of Melbourne, 2005)
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ItemA genetic evaluation of dystocia in Australian Holstein-friesian cattle(University of Melbourne, 2004)This thesis presents the first large-scale study of the genetic and non-genetic influences on dystocia (calving difficulty) for dairy cows in Australia, and their costs, focusing especially on the Holstein-Friesian breed, but also with some analyses of frequently occurring crossbreeds. Analyses used data collected since 1986, collected by the Holstein-Friesian Association of Australian and the Australian Dairy Herd Improvement Scheme. The calving traits examined were gestation length, calf size, dystocia (measured as any or none, severe or none, and none, slight and severe). I investigated the influence on calving ease of non-genetic variables such as month of calving, cow age or parity, calf sex, and breed of cow and bull. The genetic parameters were estimated: the heritabilities and genetic correlations between traits calculated, separately for primiparous and multiparous, and for sires, maternal grandsires and the maternal effects. Costs associated with dystocia (such as labour costs, loss or fertility, veterinary costs and deaths of cow and or calf) are estimated, and a cost model for dystocia under Australian conditions is proposed. The influence of crossbreeding on calving was investigated, especially with respect to dystocia and calf mortality. Recommendations are made for improving the recording system and the evaluation of bulls, as the sire of calf and as the sire of cow.
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ItemWeeds in Victorian landscapes(University of Melbourne, 2007)
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ItemModelling spatial variability of wheat yield in the Victorian Southern Mallee(University of Melbourne, 2007)
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ItemNo Preview AvailableAustralian plants as hedges(University of Melbourne, 2007)
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ItemNo Preview AvailableDeveloping a reintroduction program for the threatened terrestrial Orchid Diuris fragrantissima(University of Melbourne, 2006)Diuris fragrantissima D. L. Jones et M. A. Clem. is a perennial terrestrial orchid endemic to the state of Victoria, Australia. The species is listed as Critically Endangered in Victoria under the criteria of the International Union for the Conservation of Nature and Natural Resources (IUCN), having suffered a severe population decline since the 1930s. A recovery plan for Diuris fragrantissima has been developed by the Department of Sustainability and Environment (DSE) which includes reintroduction as an important conservation strategy. There is, however, limited research on terrestrial orchid reintroductions, and most of the previous reintroductions reported have been unsuccessful. This study investigated the taxonomic status, genetic diversity, fungal symbiont and ecological requirements for the reintroduction of Diuris fragrantissima. Phylogenetic relationships between D. fragrantissima and some closely related Victorian Diuris species was assessed by direct sequencing of the nuclear ITS and plastid trnT-F regions. Low numbers of maximum parsimonious trees (MPTs), high congruence and strong bootstrap support for clades in both separate and combined analyses indicate that Diuris is monophyletic, with the exception of D. sulphurea, which had uncertain placement. Yellow and purple flowered Diuris species formed well supported monophyletic sister clades. Purple flowered species, including D. fragrantissima were unresolved. Morphological and genetic relationships between species in the D. punctata complex were further investigated at population level using morphometrics and Amplified Fragment Length Polymorphisms. Morphological and genetic datasets were congruent in showing that purple-flowered species formed individual phenetic clusters and that D. fragrantissima was a distinct taxon. D. daltonii clustered within D. punctata, showing that the recent elevation of this variety to species level in 2004 was unwarranted. Levels of genetic variation were comparable between in situ and ex situ D. fragrantissima and its closest relatives. Gene flow was detected among all species (Nm=2.34) and populations (Nm=0.65). Fungi were successfully isolated from ten populations of five Victorian Diuris species. Three fungal isolates (from D. punctata, D. dendrobioides and an ex situ D. fragrantissima plant), germinated seed of D. fragrantissima. Ten fungal isolates were recovered from asymbiotically propagated ex situ D. fragrantissima, nine of which were mycorrhizal, with the ability to induce host seed germination in vitro. Mycorrhizal fungi were also isolated from protocorms and in situ adult D. fragrantissima. Germination percentages were below 55%. Germination was not affected by subculturing. All fungal isolates had ITS regions of at least 94% similarity to Tulasnella calospora. ITS and nLSU sequence data were congruent in showing that all fungi isolated in this study formed a monophyletic clade with high boostrap support. Therefore, although not highly specific for certain isolates, the genus Diuris appears to be specific to a narrow taxonomic group of Tulasnella species in Victoria. Genetic similarity was found between fungi isolated from D. fragrantissima protocorms and adult in situ and ex situ plants. Experimental reintroductions, involving source ex situ D. fragrantissima, showed that plant survival was greater when reintroduced as actively growing seedlings (mean = 49%) rather than dormant tubers (mean = 16%). Tuber size was positively correlated with plant size and health. A combination of support inoculum and soil aeration significantly improved plant growth and survival of spring reintroduced plants but had no significant effect on plants reintroduced in autumn. Fungal inoculum support alone did not improve plant growth or survival in either planting time. Fungi present in plant roots at the time of reintroduction were sufficient to support the transition from nursery to field. Optimum monitoring dates for reintroduced D. fragrantissima were determined to be July, when most plants were emergent, and late October to early November, when stem height and flowering were at their greatest. Fungi were isolated from plants one year after reintroduction, and identified as having ITS regions of >98% identity to isolates from ex situ D. fragrantissima, showing that mycorrhizal relationships persisted in situ. Nine of ten sampled plants in treatments with support inoculum were found to have become associated with the support inoculum, showing that D. fragrantissima was able to form new associations with fungi in situ. This study was successful in developing a reintroduction program for Diuris fragrantissima, by investigating the taxonomic status, morphological and genetic relationships in the Diuris punctata species complex, and their mycorrhizal relationships. The information obtained from this research was used to implement experimental reintroductions of D. fragrantissima, which have survived for over a year, including two dormant seasons.
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ItemMicropropagation and population diversity of the Gymea lily, Doryanthes excelsa(University of Melbourne, 2006)
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ItemNo Preview AvailableSulfur assimilation in Vicia sativa L. : molecular and biochemical characterization of a putative o-acetlyserine (thiol) lyase gene(University of Melbourne, 2006)A putative OAS-TL gene was successfully isolated, cloned, sequenced and characterized from Vicia sativa L. cv. Blanche Fleur. The gene, designated Voas-t15 (GenBank Accession No. DQ456491), was 871 bp long comprising 68 amino acids. The gene was found homologous to Arabidopsis CS26 (GenBank Accession No. NM_111234.3) at the nucleotide level. However, the degree of homology with other plant OAS-TL genes was low and the sequence lacked important protein domains. This was attributed to the high GC regions of the template, which may have led to an incomplete sequence. Phylogenetic analysis clustered the Voas-t15 sequence with other cytosolic OAS-TL genes in the Bsas 5 subgroup. Further evidence that the gene was potentially active and the product localized in the cytosol was gathered through differential centrifugation and OAS-TL enzyme assays. The OAS-TL activity measured in the cytosol accounted for 46% of the total activity. The amount of protein in the chloroplast was 32.2 .tg/mL, which accounted for 76% of the total protein content of the extracted tissue. A 52-kD protein band was detected from the plant cytosolic fraction using native PAGE and OAS-TL enzyme activity staining. Using real-time PCR, differential transcription of Voas-t15 was detected in both leaf and root tissues as a response to sulfur stress. Transcription levels were generally higher in the leaves than roots most probably because the enzymes and reactions of the sulfate assimilation pathway are located in the chloroplasts. The gene copy number of Voas-t15 was determined to be singular using Southern hybridization and digoxigenin labeling. The probable function of the gene was indicated by over-expression of the full length Voas-t15 sequence in the E. coli NK3 mutant strain, lacking the ability to synthesize cysteine. The resultant transformed bacteria were able to grow in minimal media lacking cysteine. Understanding the molecular and biochemical properties of enzymes involved in the plant sulfate assimilation pathway, such as OAS-TL, can be applied to the future development of crops with greater agricultural productivity.