School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemOestrogens, isoflavones and the oestrous cycle of the ewe( 1972)The experimental work presented in this Thesis was carried out while the author was a recipient of a Commonwealth Post Graduate Scholarship. The supervision of the experimental work in Chapters 3 to 6 inclusive was delegated to Mr. I.A. Cumming and his willing help, advice and collaboration is gratefully acknowledged. Material contained in these Chapters was obtained from experiments carried out at the S.S. Cameron Laboratory, State Research Farm, Werribee, Victoria. Chapters 7 and 8 report results of Field Trials conducted in collaboration with Mr. J.M. Obst and the Officers of the S.A. Department of Agriculture, and Drs. R.J. Lightfoot and J.F. Smith and the Officers of the W.A. Department of Agriculture, respectively. The experimental programmes in the latter two chapters were mainly financed by the Australian Wool Board Funds allocated to my supervisor, Dr. J.R. Goding. The material presented in Chapters 4, 6 and 8 has been presented to the meetings of the Australian Society for Reproductive Biology (ASRB), 1971, and the Fourth Asia and Oceania Congress of Endocrinology, N.Z., 1971. The abstracts are listed at the end of the Preface. The general facilities of the State Research Farm, Werribee were made available for these studies and the author wishes to thank the Officer in Charge of the S.S. Cameron Laboratory, Dr. P.D. Mullaney and the past Acting Officer in Charge, Mr. A.D. North. Thanks must also be offered to Mr. J.B. McPherson, Manager of the State Research Farm and his staff for assistance in the purchase, feeding and general management of the flocks of sheep used for these studies. I would like to acknowledge the help and support received from my supervisor, Dr. J.R. Goding during the past two years, but particularly to thank him for his invaluable assistance and encouragement during the preparation of this manuscript. Dr. J.M. Brown and her technical assistants Misses J. Fratantaro and E. Renden generously performed the majority of the LH assays. The progesterone assays were done with the assistance of Miss B. Sinnott and under the guidance of Mr. J.M. Obst of the S.A. Department of Agriculture. Mr. G.J. Gyory of the Victorian Department of Agriculture carried out the isoflavone analyses, and Mr. R. Jardine also of the Victorian Department of Agriculture carried out the statistical analyses. Most of the experimental procedures required labour 24 hours a day and this was willingly provided by Agricultural Officers of the Victorian Department of Agriculture. My thanks and appreciation to Messrs. R.W. Baxter, T. Howard, W.B.H. McGregor, A.W. Makin, R.A. Parr and A.H. Williams. Assistance for these experiments was also given to me by my colleagues, Dr. M.A.deB. Blockey, Mr. L.P. Cahill, Dr. M. Cain, Mr. J. Cerini, Mrs. M.E.D. Cerini, Mr. W.A. Chamley, Mr. I.A. Cumming, Miss M.A. Curtis and Miss B.J. Mole. Invaluable technical assistance was given by Mesdames D. Baxter, M. Perry and Misses J. Fratantaro, E. Renden and E. Wilson. A special thank you must be offered to Mr. P. Langdon for the outstanding technical assistance and generous help which made so much of this work possible. The photographic work was done by Mr. W. Douglas and Mr. D. Rizzoli. Mrs. H. Constable typed all the drafts of the Thesis and the final manuscript was typed by Mrs. Adele Dowling. My thanks to all who have assisted me over the last two years.
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ItemThe role of early vigour in the adaptation of canola to a Mediterranean climate( 2002)Dryland crop production in the Victorian Wimmera is restricted by water availability, particularly after flowering, as generally occurs in a Mediterranean climate. Vigorous early crop growth has been suggested as an important trait for crop adaptation to this climate. Field experiments, simulation modelling and pot experiments were carried out to study the importance of early vigour (EV) for canola growth and yield in a Mediterranean environment. The field experiments demonstrated that EV influences subsequent crop growth. In the first field experiment comparing twelve canola cultivars, EV was significantly correlated to shoot dry matter at the beginning of flowering. Similarly, the difference in EV between a vigorous (Dunkeld) and a less vigorous (Pinnacle) cultivar was maintained throughout the growing season in three other field experiments. Differences in EV due to increased density also influenced crop growth, with the exception of high density, which had higher growth early in the season but was equalled at later growing stages by normal density. Differences in EV also affected the competitive ability of canola. The study has shown that there are various options available to improve the competitive ability of a crop. These are selecting a more vigorous cultivar or adjusting management by increasing the sowing density or by applying nitrogen. Differences in EV due to cultivar or density differences did not result in different water use at any of the growing stages in the field experiments. The simulations also showed that until the beginning of flowering there were no differences in total water use between crops of vigorous and less vigorous cultivars. Thus, this study has found that vigorous cultivars did not deplete the soil to a greater extent up to flowering than less vigorous cultivars. As Dunkeld produced greater shoot dry matter than Pinnacle, it had greater water-use efficiency. This was the consequence of greater transpiration efficiency as well as lower proportion of evaporation in evapotranspiration of Dunkeld, as shown in the simulations. Dunkeld was able to compensate for low density because it was vigorous from early in the growing season. Therefore, differences in EV due to management (sowing density, nitrogen fertilizer) did not influence yield. For Pinnacle, however, which had much slower growth, differences in EV did influence seed yield. High EV due to genotype resulted in greater or similar yield than low EV in the experiments and simulations. Differences in EV in an indeterminate crop such as canola seem to influence yield less than in a determinate crop such as wheat in a Mediterranean climate. Although the simulations have shown that low EV crops can have similar yields than high EV crops under the current management practices used, there were no yield reductions found due to vigorous early growth. Pot experiments showed that differences between Dunkeld and Pinnacle at the very early stages can be attributed to differences in radiation-use efficiency alone. Later, when competition between plants commences, both specific leaf area and partitioning of biomass seem to take effect adding to the existing differences in shoot dry matter per unit area and leaf area index between the two cultivars.
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ItemResynthesis of Brassica napus to provide useful traits for canola breeding( 2002)Canola is an important oilseed crop in Australia. Lack of genetic variation in canola for economically important traits hampers efforts to breed for elite lines competitive on the world markets. An alternative approach for improvement of canola is to tap the genetic variation present in the progenitor species of B. napus and transfer novel genes into canola lines. In this study, the progenitors of B. napus (B. rapa and B. oleracea) were screened for tolerance to manganese toxicity, shatter resistance and blackleg resistance with the aim to transfer these traits through resynthesis of B. napus. Genotypes of B. rapa displayed the best tolerance to manganese toxicity in a hydroponics sand culture bioassay. The inheritance pattern of tolerance to manganese toxicity in B. rapa strongly suggested the presence of a single gene control for this trait with incomplete dominance. In the studies to screen for siliqua shatter resistance, increased energy levels of siliqua shatter were observed in B. oleracea genotypes compared to B. napus. To identify molecular markers linked to shatter resistance in B. rapa, a segregating population derived form the cross DS-17-D by Torch, was screened using RAPD, ISSR and AFLP techniques. Two AFLP markers were identified that showed strong linkage to shatter resistance. To identify new sources of blackleg resistance, several B. oleracea and B. rapa accessions were screened in field trials. B. oleracea genotypes were more resistant to blackleg showing a high level of survival (30-80%) compared to the genotypes of B. rapa. Interspecific crosses were made between selected genotypes of B. oleracea and B. rapa, and hybrid embryos were rescued using ovary culture. The genotypic profiles of hybrids and the parental lines were ascertained with RAPD primers and flow cytometry. Synthetic B. napus lines were backcrossed to canola to begin the introgression of specific traits of interest into canola germplasm. Preliminary screening of synthetic hybrids derived from interspecific crosses between B. rapa and B. oleracea showed the same degree of manganese tolerance and L. maculans resistance as the resistant parental genotypes. BCi to B. napus retained the transferred resistance and tolerance traits of the synthetic hybrids. The presence of SCX-7 marker linked to one of the shatter resistance genes sh2 in the synthetic hybrid SH2 indicated the successful transfer of shatter resistance from B. rapa as this marker expressed itself in B. rapa genotype Chitose which is one of the parents of synthetic hybrid SH2. Results of this study show that synthetic alloploids are of great practical value as they provide an extended range of genetic variability combining the variations available in diploid parents.
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ItemHaploid and zygotic embryo culture of chickpea (Cicer arietinum L.)( 2002)There are two main obstacles to chickpea improvement: 1) the long period of time between the breeders first cross and commercial release of an improved cultivar and 2) a law level of diversity in the cultivated chickpea germplasm. The aim of this study has been to develop tissue culture techniques to enable the in vitro induction and/ or growth and germination of isolated haploid and zygotic embryos of chickpea in order to assist chickpea breeders in overcoming these breeding constraints. Protocols to enable the production of homozygous breeding material via doubled haploid techniques in chickpea would speed the development and commercial release of improved cultivars. In this study, intact anther and microspore culture techniques were assessed for developing doubled haploid populations. The culture of intact immature anthers yielded callus from all fifteen chickpea genotypes tested. The composition of the MS-based callus induction medium was identified as the most important factor influencing callus induction frequency. A sucrose concentration of 0.075 M was optimum for callus induction and the plant growth regulator 2,4-D was identified as a potent inducer of callusing from intact anthers of chickpea. Upon the withdrawal of the 2,4-D somatic embryogenesis, rhizogenesis and plantlet regeneration was achieved from the callus of a limited number of genotypes. Cauliogenesis was observed from the anther-derived callus of genotype Bumper cultured on callus induction medium containing 2,4-D. Callusing was also achieved on an MS-based culture medium without the addition of plant growth regulators, however this callus did not produce somatic embryos. The addition of the ethylene inhibitors silver nitrate and silver thiosulphate and the amino acids L-proline and L-serine appeared to enhance the induction of callusing from anthers cultured on medium without plant growth regulators, however the exact role of these compounds remains unknown. Activated charcoal was completely inhibitory to callusing from intact anthers in this study. Although subordinate to the composition of the callus induction medium, the genotype of the donor plant also influenced the success of anther culture attempts. The kabuli genotype Bumper was identified as particularly responsive to callusing, embryogenesis and plantlet regeneration from intact anthers. Donor plant growth conditions, i.e phytotron or glasshouse, were not observed to have a significant effect on callusing response. Cold pretreatment of the buds for at least 48 hours prior to culture was found to improve the callusing response from anthers. Centrifuging the bud, the size of the bud when harvested and the orientation of the anther had no effect on callus production. The culture of isolated microspores yielded embryos from seven chickpea genotypes. The isolated microspores underwent division to the globular embryo stage when cultured on a membrane supported by solid MS-based medium. The microspores were plated on this membrane in discrete droplets of liquid medium (modified MS medium + 4.5 pM 2,4-D) at a density of 1 x 106 microspores mL-'. Starving the cultured microspores of carbon and/ or applying a 4C pretreatment for a period of 96 or 192 hours enhanced embryogenesis. The effect of either stress on embryogenic response was clearly genotype dependent. Genotype Bumper was more responsive to the carbon starvation treatment whereas genotype Yuma had a requirement for a cold pretreatment period in order to undergo microspore division. The culture of selfed in-ovule zygotic embryos harvested eight days after pollination from C. arietinum and C. pinnatifidum yielded complete plantlets. A MS-based medium combining the plant growth regulators thidiazuron (1 pM) and zeatin (1 pM) was identified as the most effective for the growth and germination of the embryos to plantlets across both species. C. pinnatifidum was far more responsive to in-ovule embryo culture that the cultivated species. Intercoupled plasma analysis of the composition of selected elements within the endosperm of five annual Cicer species identified clear differences in composition between the five species and the MS nutrient salts. At both 12 and 16 days after pollination, the Cicer endosperm across the five species contained much higher concentrations of the major elements phosphorus and potassium and the minor elements sodium, iron, copper and zinc than the MS medium. The osmotic pressure of the endosperm was shown to decrease as the embryo progressed in age from 8 to 16 days after pollination. The research reported in this thesis indicates that chickpea is amenable to both haploid and zygotic embryo culture. Further research should enable these techniques to be adapted to use in conventional breeding programs.
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ItemVegetative propagation of Acacia melanoxylon R. Br. through root cuttings( 2000)A method of vegetative propagation of Acacia melanoxylon using root cuttings was trialed to identify the best treatment combinations. Ten individual trees from three distinct provenances were selected. The other factors were pre-treatments including hormones and season of collection of root cuttings. Provenances were from near Canberra and the East Gippsland and the Otways region of Victoria. The different media trialed included a commercial propagation mix, sand, and a mixture of perlite and vermiculite. Five different pre-treatments were investigated to determine if they boosted the number of shoots produced from a root cutting. The whole trial was repeated over four seasons in one year. Results showed that the provenance varied significantly in the number of shoots produced from root cuttings. One medium (Burnley Mix) also gave significantly better results than the other two media. One of the pretreatments the hormone (IBA) retarded shoot growth significantly. Season of collection had the most significant impact on shoot production. Cuttings set in autumn produced more than twice as many shoots as the cuttings set in the other seasons. A histological investigation was undertaken to determine the origin of the shoots. It was found that the cells originated from the vascular cambium region of the root sections. This thesis has demonstrated that mature Acacia melanoxylon trees can be vegetatively propagated successfully and produce morphologically juvenile plants. The method if further refined could produce the consistent results required to allow commercial propagation of Acacia melanoxylon.
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ItemAn evaluation of the role of extension in the Australian pig industry( 1978)Australian agriculture is adjusting to changes in technology, economic circumstances and markets. Extension services as much as the producers' need to change in response to changing industry needs, market trends and consumer demands. There has been much discussion on the problems that these changes present for extension, but none on the basis of empirical research or social science theories. A research program was developed to define the changes taking place in the structure and organisation of the Australian pig industry, and to identify the implications of these changes for pig producers and for extension agencies such as State Departments of Agriculture. The conclusion drawn from the review of the industry situation and from a Delphi survey of 10 experts in the pig industry was that the industry will become more technical and commercialised requiring continual adaptation by the producers to technical and economic changes in order to maintain and increase production efficiency. The survey results showed that a degree of assistance from research and extension was expected by producers to help them maintain and improve production efficiency. Based on the Theory of Personal Constructs, Kelly (1955) an interactive psychological testing procedure known as the Repertory grid was used to record producers' and extension officers' perceptions of each other and of extension services. Twenty pig industry officers, 16 non extension users, 20 extension users and 16 large commercial producers were interviewed. Separate analyses were carried out on the grids of individual subjects, providing profiles of constructs typically used by the subjects in relating to and evaluating people. The results clearly identified the constructs which farmers used in relating to extension advisers and advice. In general, all groups of subjects tended to stereotype people with whom they associated. Combination of both the results within subject groups revealed evidence of commonality within and between the groups in their perceptions. The extension officers saw themselves as progressive and useful while a large number of the producers saw them as theoretical and irrelevant. Extension users held favourable attitudes towards professional agricultural advisers, while large commercial producers and non extension users criticised them on the grounds that they were difficult to communicate with and lacking practical experience. As a group, extension officers were not aware of the questioned relevance of their advice nor of the difficulty experienced by producers in communicating with them. Owing to their practical background and shared experiences, all producers saw other producers as useful and as the most relevant source of advice. The roles they expect him to perform and the characteristics that producers expect from a professional extension adviser have been identified and their implications for the extension officer are discussed. The most obvious implications of the findings are that extension advisers fail to establish the relevance of information within the farmers' context of what is relevant. Based on the findings of the research the theory is proposed that extension programmes will be most successful when producers and extension workers share common perceptions of relevant problems. A philosophy and practice of extension is proposed to meet the farmers' own perception of needs. The interpretation of the results in terms of Personal Construct theory leads to the development of the model of human behaviour, that is, "man as an actor" instead of "man as something being acted upon". A philosophy of extension is developed based on the belief that extension can only be successful if it provides what farmers want. The philosophy states that extension should provide a helping role by facilitating, developing and supporting "man the actor" without dominating or controlling his actions. A practice of extension operating within the boundaries of the proposed new philosophy is developed from the helping relationship model of Carkhuff (1969). The goals of extension are defined as exploration, understanding and action which lead directly to the need for skills which are defined as the "interface skills" of attending, responding, personalising and initiating. The need for and the nature of extension training to provide extension officers with "interface skills" is discussed.