School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemNo Preview AvailableControl of the black field cricket teleogryllus commodus (walker) (orthoptera: gryllidae) in Victoria(University of Melbourne, 1985)Techniques for improving control of the black field cricket Teleogryllus commodus were studied between 1981 and 1985 in series of laboratory and field trials in the western district of Victoria. In the laboratory, techniques were developed for assessing the palatability of substances to T. commodus. A number of plant extracts, especially water and acetone extracts from grasses, and other substances including sucrose and vegetable oils were shown to stimulate feeding in the cricket. Further laboratory trials showed that feeding stimulants could be used to encourage feeding on a commonly used substrate in cricket baits (wheat). Field trials to assess bait attractiveness revealed oats to be more attractive as a bait than wheat or barley. Efficacy trials conducted over consecutive years however, showed no differences in the level of control achieved with baits using wheat, oats or barley as the substrate. In addition, feeding stimulants added to the bait did not improve control, nor did the use of higher baiting rates. The level of control obtainable with the current recommended bait is between 80% and 95%.
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ItemNo Preview AvailableGenotype environment studies in Pisum Sativum L. in relation to breeding objectives : ideotypes of pea(University of Melbourne, 1981)The overall objective of this thesis is to provide the information necessary to produce new varieties of pea which are more productive, easier to harvest and better suited to present day markets. This thesis defines ideal plant types (ideotypes) of pea and outlines how a breeding programme could produce and test them. Some effects of genotype and environment on morphology, development, growth, nodulation and yield component interactions are documented. Sets of near-isogenic lines, segregating populations and collection lines were grown in environments varying for photoperiod, temperature, daily radiant flux and soil nutrient levels. The results obtained, and reviews of the literature, provided the knowledge necessary to specify ideotypes. The ideotypes are defined at two levels: 1. Traits which confer benefits in terms of increased general adaptation to cropping systems, and 2. Traits which are specific to particular cropping systems and product uses. Increased general adaptation of pea should result from changes to plant form (e.g., leaflets replaced by tendrils, pods clustered at the top of the plant instead of being spread along the stems) and appropriate manipulation of yield components (e.g., high number of seeds/pod rather than many pods/node). Also, total yield of agricultural products from a crop rotation system will depend, in part, on the nitrogen fixing, ability of the pea crop. The time of flowering is an important trait conferring adaptation to specific cropping systems. The ideotypes have a condensed flowering period compared with current cultivars, so it becomes critical that flowering occurs at the optimum time. Models to predict the time of flowering from climatic data are presented for a range of genotypes. Other traits required in specific situations are determined by aspects such as market preferences and disease and insect problems. The genetic control of most of the ideotype traits is known and is relatively simple, so new plant types could be produced rapidly. A breeding programme based on the ideotype concept could use backcrossing to a recurrent parent to combine the desired traits into one plant type. It would be wise to do this on a range of genetic backgrounds and it would be necessary to test the new plant types for negative gene interactions and detrimental pleiotropy.
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ItemNo Preview AvailableThe soil-root interface of Lupinus Albus L. and its significance in the uptake of manganese, iron, and phosphorus(University of Melbourne, 1981)It has been demonstrated using an agar film technique that L.albus is able to dissolve colloids of iron/silicate, iron/ phosphate, aluminium/silicate and aluminium/phosphate and also suspensions of manganese dioxide, calcium mono-hydrogen phosphate and ferric hydroxide. Dissolution of these compounds was most marked in proteoid root regions of lateral roots (dense clusters of 20 laterals of limited growth) and certain regions of the tap root. Soil associated with these root regions was found to contain more protons, reductants and chelating agents than the bulk soil. The effect of iron and phosphorus nutrition was examined in acid washed sand. The effect of phosphorus nutrition was also examined in three soils (acid, neutral and alkaline) under glasshouse conditions. The response of wheat, L.angustifolius and L.albus to phosphorus was compared at three sites (acid, neutral and alkaline) in field trials. Proteoid root formation was found to be predominantly controlled by the phosphorus status of the plant. Manganese uptake in L.albus was related to proteoid root formation, and inversely related to phosphorus supply in both L.albus and L.anqustifolius. The ability of L.albus to utilise soil and added phosphorus decreased as the pH of the soil increased. The role of micro-organisms in proteoid root formation and function was investigated. Proteoid roots formed under sterile conditions, but more formed under non-sterile conditions. The effect of varying root morphology on exudation characteristics in the rhizosphere was examined by computer simulation. The main exudate from the roots of L.albus has been identified by gas-liquid chromatography and mass spectrometry as citric acid. It is hypothesised that citrate ions react with the soil colloid and form a diffusible polymeric ferric hydroxy phosphate which moves to the root surface where it is broken up by a combination of ferrous ion uptake, proton secretion and reduction. An attempt has been made to examine iron in the roots using electronmicroscopy and X-ray microprobe. The results suggest that iron is mobilised about the root system in large amounts, although this is not reflected in above ground parts. The effect of intercropping wheat and L.albus was examined in both glasshouse and field for effects on the mineral nutrition of both species. Wheat intercropped with lupins appears to have access to a larger pool of available phosphorus, manganese and nitrogen than has wheat grown on its own.
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ItemNo Preview AvailableAspects of the biology and salt tolerance of Phragmites australis (Cav.) Trin. ex Steud.(University of Melbourne, 1980)Reeds thrive under a wide range of conditions, but in the Gippsland Lakes system, high salinity levels - both alone and in conjunction with other environmental factors - have greatly reduced Phragmites growth on the shoreline and removed the reed fringe entirely in some areas. The Gippsland Lakes system provides an unstable environment, where salinity levels and water levels fluctuate seasonally and also between drought and flood years. Distribution of reeds along the lake edges is correlated primarily with salinity levels, but also with exposure to wind, wave and current action. The amount of salt absorbed by reeds is directly related to site salinity. High salinities reduce many aspects of productivity, including shoot height, density and dry weight, and seed production. The actual salinity tolerance of Phragmites in the field is dependent upon the severity and duration of the salinity regime and other habitat factors operating. Conditions on the north shore of Lake Wellington are near the tolerance limit of Phragmites. Reeds accumulate large quantities of mineral elements and growth is greatly improved in areas of high nutrient status. Phragmites can readily be grown from rhizome or shoot cuttings if these are collected at the appropriate stage of development. Establishment from seed is a rare occurrence in the field and germination depends on the formation of viable fruits. In the three Victorian populations studied, less than two per cent of the florets contained viable seed.
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ItemThe effect of exogenous oestrogens on luteal function and sexual behaviour in mares( 1981)The early and accurate diagnosis of pregnancy is essential for efficient equine stud management. The early identification of non-pregnant mares is important for minimizing delays in rebreeding thereby reducing the period of intensive stud management and the inter-foaling interval. An early test for the diagnosis of pregnancy/ non-pregnancy would also provide information relating to the occurrence of abnormal corpus luteum (CL) function and early embryonic mortality, two conditions commonly seen in mares (Day 1939, Nishikawa 1959, Rossdale 1969, Allen 1972, Hughes et al 1972, Allen et al 1974, Stabenfeldt et al 1974, Palmer 1978). The most common methods of pregnancy diagnosis are performed 40 to 45 days post-service. The methods used are rectal palpation (Lensch 1961a, 1961b, Van Niekerk 1965a, Bain 1967a, 1967b, Solomon 1971, Voss et al 1973, Allen 1974, Parker et al 1975, Voss & Pickett 1975) and measurement of pregnant mare serum gonadotrophin (PMSG) (Wide & Wide 1963, Jeffcott et al 1975). Neither method is 100% accurate in the detection of either pregnant or non-pregnant mares (Allen 1969, Allen 1974, Jeffcott et al 1969, Mitchell 1970, Solomon 1972,.Luttman & von Lepel 1973, Parker 1975). Plasma progesterone values between days 18 and 26 post-service indicate the presence of a functional CL but not necessarily a CL of pregnancy (Squires et al 1974a, 1974b, 1975, Van Niekerk et al 1975). There is then a definite requirement for an early and accurate test for the diagnosis of pregnancy and the detection of non-pregnancy. The oestrogen treatment test (OTT) was first used for the early diagnosis of pregnancy in mares by Nishikawa in 1952. The lack of oestrous behaviour after treatment with 3 to 5 mg stilboestrol diproprionate (S) on day 17 to 20 post-service was claimed to be 95% (Reddy.& Khan 1976) to 100% (Nishikawa 1959) accurate in the diagnosis of pregnancy. But, there is evidence from other species to suggest that exogenous oestrogens can cause luteolysis and. abortion in pregnant animals and interfere with cyclic activity Of served non-pregnant animals. Since both pregnant and non-pregnant mares receive S in the OTT it was considered important to. determine the effects of S on luteal function in both pregnant and non-pregnant mares. There is insufficient evidence relating to the effects of exogenous oestrogens. in. non-pregnant mares but several reports have shown a . variety of both physiological and behavioural effects to occur in other species depending on the dose rates used and the parameters studied. The main, aims of the research reported in this thesis were: (i) The establishment of a radioimmunoassay for progesterone as a means of assessing luteal function (ii) to define the effects of stilboestrol diproprionate on luteal function and sexual behaviour of pregnant and non-pregnant mares (iii) to determine the efficacy of the OTT as a test for .pregnancy diagnosis when used alone or in conjunction with other methods currently in use (iv) to investigate the mechanisms by which exogenous oestrogens may interfere with luteal function in mares.
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ItemAspects of the growth of wheat in relation to soil moisture( 1984)An initial experiment compared the effects on root growth of wheat of simplified methods of cultivation and sowing i.e.; minimal tillage, and traditional cultivation. Differences between simplified and traditional cultivation occurred in root distribution in the surface layer, but these differences had no evident effect on top growth and all treatments produced similar grain yields. In later experiments, the effects of water stress on root growth were investigated in two varieties of wheat, Triticum aestivum, - var. Gabo and var. Olympic. Water use and water use efficiency (WUE), and the effect of water stress on yield and its components were investigated. In both varieties, water stress reduced top growth and yield, and growth of roots. The extent of the growth reduction reflected the severity of the water stress. Pre-anthesis water stress reduced the number of grains per spike as well as the number of effective tillers. Post-anthesis water stress tended to reduce grain weight. There was a linear relationship between water use and grain yield, and between water use and shoot dry weight production. Water use efficiency (WUE) was found to increase as water use decreased. WUE based on total water use was found to depend on the severity and duration of water stress, the growth stage at which water stress occurred and on the subsequent availability of water to the plant after water stress. Within treatments, the two varieties used almost the same total amounts of water to produce generally similar total biomass but higher grain yield for Gabo. However, WUE for grain yield and total biomass was significantly greater for Gabo than for Olympic.
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ItemSelection for salt tolerance in lucerne (Medicago sativa L.) using tissue culture( 1984)Studies were made of the influence of four different levels of NaCl (0, 75, 150, 250, mM) on the growth of callus of five lines of lucerne (Medicago sativa L.). These lines were based on the U.S.A. cultivar CUF 101 and comprised an unselected population and two populations selected for NaCI tolerance through one (line T-1) and two (line T-2) cycles of recurrent selection and two populations similarly selected for NaCI sensitivity through one line (line S-1) and two (line S-2) cycles of recurrent selection. Calli of the five lines, derived from the hypocotyl tissue, were exposed to NaCl by transferring them to various concentrations of NaCl. While it appeared that callus of salt-tolerant lines under certain levels of NaCl were somewhat less affected by NaCl than the "non-tolerant" lines, there was no marked general relationship of the reputed differences in whole plant tolerance the lines and the callus tolerance to NaCl. An experiment was conducted to further examine the relationship between whole plant salt-tolerance of unselected CUF 101, and its salt-tolerant (T-1) and the salt-sensitive (S-1) lines and callus derived from their plants. It revealed moderately high positive correlations between a number of measures of seedling growth and callus fresh weight when both were exposed to similar ranges of NaCI concentration. This thesis study gave no strong evidence that salt tolerance in lucerne is consistently expressed in the callus and that tolerance to NaCl concentration at the cellular level, which is likely to be the main basis of callus tolerance, is a very significant component of whole plant tolerance to NaCl. Regeneration of plants was induced in callus that had been exposed to NaCl on a solid (agar) Boi2Y medium. Regeneration was obtained from callus of unselected CUF 101 after exposure to 75 mM NaCI and the salt-sensitive line (S-1) after exposure to 150 mM NaCl. Regenerated plants were grown to maturity. Plants regenerated from the same callus were artificially intercrossed to provide seed of regenerated populations which were grown to examine them for the presence of somaclonal variation, both for salt tolerance and plant morphological characters. No significant change was detected in variation for salt tolerance in the progenies of regenerated plants compared with respective normal "parent" populations. However, increased variation was observed in regenerated populations for a number of plant morphological characters such as leaflet number, size and shape.
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ItemNitrogen transformations in soils during nitrification of alkaline-hydrolysing fertilizers( 1985)Nitrogen transformations occuring in urea-fertilized soils during nitrification were studied in laboratory experiments. Nitrite accumulated in the majority of soils fertilized with urea, and the maximum nitrite concentration was directly related to initial soil pH. Cumulative gaseous-N losses (% of applied N) in ten soils were: NH3, 0-59.6; N2, 0-4.9; N2O, 0-9.9; KMnO4-N, 0-1.3; CH3ONO, 0-<0.1. Losses were correlated with soil pH (NH3), maximum nitrite concentration (N2, N2O, KMnO4-N) and organic carbon content (N2, N2O). The effects of form and method of placement. of urea on gaseous-N losses were small in comparison with differences between soils. Increasing rate of urea application increased nitrite accumulation and total gaseous-N losses in an acid soil. Nitrapyrin decreased nitrite accumulation and prevented losses of N2, N2O, KMnO4-N and CH3ONO, but increased NH3 volatilization loss. Chlorate increased nitrite accumulation and losses of N2O and KMnO4-N, but did not affect emissions of NH3 and N2. On balance, total gaseous-N loss was decreased by nitrapyrin addition but increased by chlorate addition. Nitrapyrin increased the amount of N not recovered as gaseous and inorganic forms. Nitrapyrin reduced emissions of N2O in the field induced by band application of anhydrous ammonia. Methodology was developed to permit the role of CH3ONO in chemodenitrification to be evaluated. Methods for determination of methoxyl groups in soils, for the synthesis, purification and analysis of CH3ONO, and for the synthesis and isotope-ratio analysis of CH3O15NO were developed. Methyl nitrite was identified as a gaseous product of nitrite decomposition in soils. The formation of CH3ONO was directly related to nitrite concentration and soil methoxyl content, and inversely related to pH. Soil was a sink as well as a source of CH3ONO. Methyl nitrite was readily hydrolysed in soil with the formation of HNO2, and was fixed by soil organic matter. Hydrolysis and fixation of CH3ONO were inversely related to soil pH. Hydrolysis decreased with decreasing soil water content, but fixation was unaffected or increased as soil water decreased. Evidence was obtained for adsorption of CH3ONO by clays. Evolution of CH3ONO is unlikely to be a significant pathway of N loss from soil.
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ItemRole of slope in shallow flow through and over simulated vegetation( 1985)Although many investigations have been reported into the shallow flow of water over smooth surfaces in experimental flumes, relatively little work has been done on the sub-divided flow of water which moves through grass swards. The inapplicability of common equations for such flow conditions has been demonstrated by other workers and by the author using a laboratory flume with dense artificial plastic "grass" fixed into it's bed. In particular, little work has been reported on the role of slope for these sub-divided flows and this aspect is emphasised in this project. The empirical, highly flexible discharge-depth equation has been shown to be appropriate for such "mixed" flow conditions through and over the plastic grass. The exponents and constant of the equation have been studied for flow through and over vegetation with respect to flow regimes and retardance. The ranges of slope and discharge used were 0.004-0.008 and 3.0x10-2-20.0 Lm-1s-1 respectively. It was concluded that when an exponent of 0.6 is used for the slope term rather than the traditional value of 0.5 (i.e. when the Manning or Chezy equation is used in this situation), a consistent value for the resistance term then results. The discharge-depth equation should be applicable to a wide range of sheet flow conditions and waste water purification, using appropriate exponents for the slope and depth terms.
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