School of Agriculture, Food and Ecosystem Sciences - Theses

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Linkage mapping and QTL analysis of ascochyta blight resistance in chickpea (Cicer arietinum)

Galvez, Hayde Flandez. (University of Melbourne, 2003)

Ascochyta blight is the most destructive foliar disease of chickpea worldwide. Resistance is available in the germplasm, and with a strong evidence of polygenic control, breeding is geared towards gene pyramiding for durable resistance via marker-assisted selection. This thesis generally aimed to map and analyze the quantitative trait loci (QTL) which condition ascochyta blight resistance (ABR) in an intraspecific Cicer arietinum genetic background. An intraspecific population of chickpea was used to create the first linkage map for the C. arietinum genome, and locate six QTL conditioning glasshouse and field resistance to ascochyta blight. Results from QTL analysis revealed a major genomic region that contained clusters of QTL (QTL 4, 5 and 6), and minor QTL specific for glasshouse (QTL 2 and 3) and field (QTL I) resistance. Multiple interval mapping revealed that resistance of chickpea to ascochyta blight was conferred by an epistatic interaction between the additive gene action of the major QTL and the dominance gene action of the other (minor) QTL. RGA markers PTOFENb212 and CLRRinv904 were found tightly-linked to the major ABR-QTL region. By sequence alignment, the RGA markers were confirmed to be the corresponding resistance gene orthologs (RGOs) in chickpea. Allele- and locus specific SCAR markers targeting the RGOs were developed and shown to be transferable to other resistance genotypes. The RGOs were also used as starting points to isolate the underlying major genes or cluster of genes for ABR. 5'-cDNA sequences of the major ABR genes, ArFEN and ArLRR, were then characterized. These are the first candidate gene sequences for ascochyta blight resistance identified in chickpea by a map-based candidate gene approach. Based on the homology alignment of ArFEN and ArLRR, and sequence information of the RGOs with published gene sequences, the R-genes underlying the major QTL region may be classified under the third group of R-genes that contains a serine-threonine protein kinase domain, with a leucine-rich repeat. Homology alignment of the candidate genes also revealed that the mechanism of resistance reaction conferred by the major ABR genes in chickpea was most likely that of a hypersensitive response.
Expression of a recombinant mycobacterial antigen and characterization of fas-defective mutant strains in corynebacterium glutamicum and related species

Chang, Shin-Jae (University of Melbourne, 2003)

The research undertaken in this thesis had the initial aim of investigating the utility of Corynebacterium glutamicum species as host for synthesis of foreign proteins of biotechnological importance, given that earlier research had shown that this industrially-important species, normally used for amino acid production, was able to express and secrete a variety of proteins from different bacterial sources. Of particular interest was the use of this species in making proteins that may be secreted or located at the cell surface, where their expression may have been important in antigenicity or other physiological functions: proteins made and secreted by related organisms, including pathogenic Mycobacterium species, were of particular interest because many pathogens cannot he cultured readily in the laboratory environment or exist as obligate intracellular parasites. It was also likely that the C. glutamicum and Mycobacterium species would share functionality in their cell surface proteins, an assumption based on their common synthesis of mycolic acids complex surface lipids that are involved in making cells from this group resistant to chemical and physical assault. The first part of the thesis describes a study on the synthesis and secretion of the 85 antigen complex, component of which are important immunogens in Mycobacterium and are secreted proteins with activity involved in the attachment of mycolic acids to the cell wall. During the course of this study, PCR amplification using primer sets based on the 85B antigen complex from M. bovis was followed up by sequencing the PCR products. Rather than corresponding to an 85B homologue, the DNA had high sequence similarity to a fatty acid synthase (FAS) gene previously found in Brevibacterium (now Corynebacterium) ammoniagenes. The subsequent focus of the thesis was on characterization of the presumptive fas gene in C. glutamicum in terms of gene inactivation and impact on lipid synthesis, for both fatty acids and mycolic acids. The first part of this project was to undertake controls for later experiments if the mycobacterial antigen 85 complex components (A, B and C) or any homologue of these were present in Corynebacterium glutamicum AS019 and its related strains, C. glutamicum ATCC13032, C. glutamicum CG2, C. lactofermentum BL1 and C. flavum BF4. This involved determining on the expression of a recombinant antigen 85 complex in C. glutamicum AS019 and related cell-surface mutants (MLB 133 and MLB 194). In order to detect the presence of the mycobacterial antigen 85 complex (A, B and C) or homologues, several experiments, including Polymerase Chain Reaction (PCR), Southern hybridization and Western blotting experiments, were carried out. The screening focused on the antigen 85B as this component is the most abundant of the antigen 85 complex in Mycobacterium species and there is considerable similarity between antigen 85 complex members at both nucleotide and amino acid sequence levels. Furthermore, antigen 85B was most extensively studied in the literature so that the materials needed to study this (such as PCR primers, antibody and probes for Southern hybridization experiments) were easier to make or obtain from other research groups. A PCR Mal 1/21 primer set was designed based on the most conservative regions of the antigen 85B from several species of Mycobacterium. Amplification produced several feint products from C. glutamicum AS019, C. lactofermentum BL1 and C. flavum BF4, which was an unexpected outcome. All the major PCR products were cloned into the pGEM�T vector and sequenced to determine similarity with the sequence of mycobacterial antigen 85 complex. However, the �0.8 kb PCR products from C. glutamicum AS019 and C. lactofermentum BL1 showed relatively high similarity (-70%) with a fatty acid synthase gene (fasA) of C. ammoniagenes and �60% with the fasA found in M. tuberculosis. Similar PCR products were found in all of the C. glutamicum strains tested. In Southern hybridization experiments, two different probes were used for more intensive analysis. One was the 0.8 kb PCR product produced by the Mal 1/21 primer set when pGEX-MPB59 (an expression vector which contains a mycobacterial antigen 85B gene) was used as template. The other was a 0.49 kb fragment produced by PstI/Xhol double-digestion of the above 0.8 kb PCR product. Relatively lower prehybridization/hybridization temperature (55�C) and longer expose time were employed to detect any loosely-bound signal, however, no specific signal was detected using gDNA from C. glutamicum AS019 and its related strains. In Western blotting experiments, anti-antigen 85B antibody raised in rabbits was used as the primary antibody to detect any signal from whole disrupted cells and culture filtrate of C. glutamicum AS019 and its related strains. No signal was found using culture filtrates concentrated 50 fold, however, a signal was found using disrupted cells of all strains. To determine the location of this protein, cell wall proteins were extracted from whole cells with 50 mM Tris buffer containing 2% Sodium Dodecyl Sulfate (SDS). No signal was found from cell wall extracts so that this protein may be located in the inner membrane or cytosol. The size of this protein was almost 40 kDa which is significantly bigger than the mycobacterial antigen 85 complex (B is 32 kDa and A and C are 30 kDa). Even though a signal was found from Western blotting experiments, it was concluded that there was no antigen 85 complex homologues present in C. glutamicum due to the negative results from PCR and Southern hybridization experiments. Several strains were then transformed with pCGL1055, which contains the antigen 85A gene, to determine the secretion level of recombinant antigen 85A in C. glutamicum AS019, C. glutamicum MLB133, C. glutamicum MLB194, C. lactofermentum BL1 and C. flavum BF4. Since pCGL1055 had the cspB promotor, two sets of primer were used to confirm the presence of the cspB gene (coding for PS2 protein in corynebacteria) in the strains used in this expression work. To quantify the amount of secreted recombinant antigen 85A, recombinant antigen 85B was prepared as the standard using Glutathione Sepharose 4B� affinity chromatography followed by thrombin cleavage and gel filtration chromatography using material prepared from E. coli TG2 transformed with pGEX-MPB59, the expression vector which contains the antigen 85B gene. C. glutamicum MLB 133 and MLB 194 showed relatively higher secretion level than the parent strain, C. glutamicum AS019, which suggests that the changes in the cell wall structure of the mutants caused better secretion of the foreign recombinant protein. C. flavum BF4 also showed relatively higher secretion levels than AS019. Volumetric and cellular productivity for the expressed recombinant antigen 85A from several corynebacterial strains were calculated to determine the efficiency of strains in secreting the protein into culture fluids. The amount of 85A protein secreted was expressed as the equivalent of 85B protein measured in parallel using anti-antigen 85B. In volumetric productivity from C. glutamicum strains AS019 (spontaneous Rif mutant of C. glutamicum ATCC 13059), MLB 133 and MLB 194 (the cell wall modified mutants of C. glutamicum ATCC 13059) was 16-17 ng/ml. However, C. lactofermentum BL1 and C. flavum BF4 expressed relatively higher amounts of antigen 85A (22-23 ng/ml) than the above strains. Cellular productivity was determined by calculating the amount of antigen 85A secreted from the given number of cells of each transformant by adjusting the optical density of each overnight cultured culture filtrate to 100 at 600nm. The cell wall modified mutants, C. glutamicum MLB 133 and C. glutamicum MLB194, showed higher efficacy (730-775 ng/ml) in expressing antigen 85A from the given number of cells than its wild-type strain, C. glutamicum AS019 (440 ng/ml). C. flavum BF4 showed almost the same efficiency (about 750 ng/ml) as the mutants. The new finding of a fas-gene homologue using PCR amplification prompted further studies aimed at characterizing its role in synthesis of fatty acids and mycolic acids in C. glutamicum. The inactivation of a gene by homologous recombination was used to characterize the fas-gene homologue, employing the 0.8 kb fragment found in the previous PCR experiments. The 0.65 kb fragment, the nested PCR product from the above 0.8 kb fragment, was amplified using the fas11/21-EcoR I-1 primer set. The amplified 0.65 kb fragment was digested with EcoR I and cloned into pECMA, a suicide vector that does not replicate in Corynebacterium strains without homologous recombination between the insert and recipient chromosomal DNA due to the lack of a replication origin on the vector. The newly constructed suicide vector, pECMAfas-AS019, was introduced into the donor strain, E. coli S17-1, a mobilizing strain constructed by the integration of self-transmissible (Tra') plasmid, RP4 2-Tc
Evaluation of dual energy x-ray absorptiometry for predicting whole body and carcass composition of pigs

Suster, Danny. (University of Melbourne, 2003)

This dissertation aims to evaluate the dual energy X-ray absorptiometry (DXA) technique for measuring whole body and carcass composition of pigs. Section 1 provides the appropriate calibration for quantitatively accurate DXA measurements of live body and carcass composition of pigs of varying weight, as determined by chemical analysis and manual dissection. The DXA technology provided an accurate precise measurement of composition within experiments and when measurements were compared across experiments. The precision of DXA measurements were far better than weight and P2 backfat, particularly in the prediction of fat tissue, especially when measurements were compared across experiments. The DXA measurements were highly repeatable and measurement repeatability improved as animal size increased. The placement of the regional analysis grid influenced the repeatability of all measurements except for total weight, however this influence reduced with increasing animal size. It is recommended that the scan image be positioned in the arm region of the software regional analysis grid to measure whole body composition in pigs because it provides the most repeatable measure overall and a better measure for fat tissue when compared to chemical analysis and manual dissection. The DXA regional analysis software also provided an accurate and precise measurement of dissectible composition in the primal-cuts, ie. the ham, loin, belly and shoulder. However, care needs to be taken to ensure accurate and consistent delineation of sub-regions to the true position of primal-cuts in the DXA scan image to ensure a reliable measurement. Section 2 involved a series of experiments to evaluate the ability of the DXA technology in measuring the effects of various known and innovative body composition manipulators, all directly applicable to industry. Each experiment demonstrated the use of the developed calibration equations and the efficacy of the DXA technique. Overall, corrective equations were successfully applied to DXA estimates and largely corrected differences between raw DXA outputs and chemical values. The DXA measurements confirmed that diets deficient in protein lead to sub-optimal lean tissue and bone mineral growth with no effect on fat and were substantiated by chemical analysis. Serial DXA measurements in the same animal demonstrated the lifetime differences between contemporary genotype boars and barrows under different penning conditions. These data indicated that although boars have a lower propensity to deposit fat overall, under group penned conditions there is little incentive to produce boars in terms of body composition if slaughter weights were below about 80kg. However, in the late finisher period, boars did deposit more lean tissue than barrows, but this difference was reduced when animals were group-penned. The regional analysis software successfully demonstrated the effects of pST treatment on fat distribution within the animal, and was validated using manual dissection. A dose dependent decrease in belly, loin, ham and shoulder fat was also observed, although the proportionate decrease in belly fat was more pronounced than for the whole carcass and other primal cuts. Finally, the DXA technique was sensitive enough to detect the subtle body composition changes that were induced by supplemental dietary betaine. Dietary betaine improved growth rate and protein deposition, and consequently carcass lean tissue content, in pigs fed restricted energy and the effects were additive with those of pST. Lean tissue in the loin was particularly responsive. The energy spared by betaine was not enough to increase fat deposition, carcass fat or P2 backfat regardless of energy intake. However, dietary betaine did increase fat in the more energy responsive belly region under ad libitum conditions but not under a restricted intake typical of commercial conditions. Therefore, dietary betaine did alter the distribution of lean meat and fat within the animal. These data demonstrate that the DXA technology is a "viable" replacement for the standard methodologies in animal growth and body composition research experiments and has much potential for implementation into the pork industry for carcass grading and providing data for pig growth simulation models.
Remote sensing of leaf area index and land cover classification of mountain forests

Sharma, Dharam Prakash (University of Melbourne, 2002)

The use of multispectral IRS (LISS-III) satellite images for land cover classification and monitoring change dynamics of Leaf Area Index of mountain forests in winter, spring, and summer using IRS (LISS-III) satellite data for two study sites was investigated. The relationships between Leaf Area Index and band radiance / vegetation index were compared in different seasons. The relationships were closer with vegetation indices than the individual band and principal components. In addition the relationships were better for the Solan site than the Narkanda site. Winter and spring relationships were much better than summer. Comparatively, the performance of RATIO and Normalized Difference Vegetation Index was superior to other vegetation indices. To improve these relationships, various topographic corrections such as the Statistic-empirical, the C and the Minnaert correction were applied to the multispectral and multi-date satellite images using Digital Elevation Model. The visual effects were impressive, but the topographic corrections failed to improve LAI-band and LAI-Vegetation Index relationships. The utility of multispectral and multi-temporal IRS (LISS-III) satellite data in land cover classification for Solan study area using a maximum likelihood algorithm on single date as well as multi-date satellite data was investigated. The summer imagery gave higher classification accuracy of 76 per cent than a classification accuracy of 49 per cent and 46 per cent in the winter and the summer respectively. The classification based on four channel multi-temporal data merging, using a set of seven bands showing maximum categorization of land cover types produced a classification accuracy of 71 per cent. Similarly, classification based on the Principal Component Analysis, using first two principal components from each season as well as first seven principal components from multi-date data merging in the classification process obtained a classification accuracy of 71 per cent. The classification accuracy obtained in multi-temporal data merging and Principal Component Analysis approach were higher than classification based on single-date dataset of winter and spring. The topographic corrections applied to multispectral and multi-temporal datasets with an objective to improve the land cover classification reduced within category class variability and improved the visual display, but failed to generate better classification accuracy. Though the LAI and multispectral data relationships were better in winter and spring seasons at one site, the study does not support the use of satellite data to estimate seasonal difference in LAI of mountain forest. However, multi-date multispectral satellite imagery can be useful for achieving better classification accuracy of land cover type for the Himalayan region.
Characterisation of antibacterial and antiviral proteins and peptides of bovine milk

McCann, Karl B. (Karl Beaumont) (University of Melbourne, 2002)

In this study bovine milk proteins including, sodium caseinate, as-caseins, 13-casein, x-casein, a-lactalbumin, 13-lactoglobulin, lactoferrin, lactoperoxidase and serum albumin were digested with proteolytic enzymes and screened for antibacterial activity. The pepsin and chymosin digests of lactoferrin and sodium caseinate, that showed antibacterial activity, were purified using cation exchange chromatography and reverse phase high performance liquid chromatography. Characterisation of the purified antibacterial peptides from each milk protein digest by mass spectrometry, N-terminal amino acid sequencing and comparison to peptide masses of theoretical enzymic digests of milk proteins, revealed 11 antibacterial peptides with unique sequences. Four antibacterial peptides were derived from the pepsin and chymosin digests of lactoferrin. LFp1 corresponded to residues 17-41 of bovine lactoferrin, LFp2 (and LFr1) corresponded to residues 17-42 of bovine lactoferrin, LFr2 corresponded to residues 17-43 of bovine lactoferrin and LFr3 corresponded to residues 1-48 of bovine lactoferrin. Seven antibacterial peptides, Cpl, Cp2 (Cr2), Crl, Cr3, Cr4, Cr5 (Cr6) and Cr7 were isolated from the pepsin and chymosin digests of sodium caseinate, of which, Cpl, Cr3, Cr4, Cr5 (Cr6) and Cr7 have not been previously reported. The peptide, Cpl corresponded to residues 99-109 of bovine asicasein. Cp2 (and Cr2) corresponded to residues 183-207 of bovine aS2-casein, Crl corresponded to residues 181-207 of bovine aS2-casein, Cr3 corresponded to residues 180-207 of bovine aS2-casein, Cr4 corresponded to residues 175-207 of bovine aS2-casein, Cr5 (and Cr6) corresponded to residues 164-207 of bovine aS2-casein, and Cr7 corresponded to residues 172-207 of bovine aS2-casein. The minimum inhibitory concentrations (MIC) of the casein-derived antibacterial peptides were determined against a range of Gram-positive and Gram-negative bacteria. Of the caseinderived antibacterial peptides, Cr4 and Cr5 displayed the most potent antibacterial activity and demonstrated MIC values that were similar to those of nisin and lactoferricin B against selected Gram-positive bacteria. Peptide Cpl was the least active of the casein-derived antibacterial peptides, having MIC ranging from 125 to >1000 ?g mL-I . Further testing revealed that the addition of metal cations substantially reduced the antibacterial activity of both Cpl and lactoferricin B against Escherichia coli. However, the activity of Cpl was enhanced by the addition of food-grade chelating compounds including citrate and EDTA. A partially purified chymosin digest of sodium caseinate, which contained Crl, Cr4 and Cr5 as the major antibacterial peptides, was prepared and referred to as CrMIX. The antibacterial activity of CrMIX was not affected by exposure to 121�C for 15 min. Subsequent bactericidal testing demonstrated that CrMIX at a concentration of 5 mg mU1, reduced the viable counts of Salmonella enterica subspecies enterica serovar Typhimurium by up to 5-log within 2 h exposure in 0.1% peptone. However, when tested in skim milk at a concentration of 5 mg m1:1, CrMIX did not inhibit growth of Salm. Typhimurium. Preliminary studies were performed for the cloning and expression of the previously unreported antibacterial peptide, Cpl in Escherichia coli. The Cpl gene was successfully ligated into the pET-15b cloning vector, but when expression was induced, the target protein was not detected, most likely due to rapid proteolytic degradation by the E. coli host. Bovine milk proteins including, as-casein, x-casein, (3-lactoglobulin, lactoferrin, lactoperoxidase and serum albumin were assessed for antiviral activity against poliovirus (PV) and feline calicivirus (FCV). Lactoferrin showed antiviral activity against both PV and FCV, and subsequent testing using fluorescent labeled antibodies to lactoferrin revealed that lactoferrin bound to the surface of both host cell lines, consistent with lactoferrin interfering with the binding of viruses to cell receptors. In addition, the antimicrobial peptide, lactoferricin B derived from the N-terminal of lactoferrin showed antiviral activity against FCV. A range of adsorbent materials including edible silica compounds and titanium dioxide were assessed for their ability to bind bioactive milk proteins and peptides. Lactoferrin and lactoperoxidase bound to all silica compounds and titanium dioxide. In addition, it was observed that lactoperoxidase bound to the adsorbent materials retained enzymic and antibacterial activity and was more resistant to inactivation caused by high temperature, and exposure to UV light and hydrogen peroxide. The silica adsorbent material, MicroCel successfully adsorbed the cationic antibacterial peptides, lactoferricin B and CrMpc However, both peptide preparations did not show antibacterial activity when bound to MicroCel. Lactoferrin and lactoperoxidase could be eluted from selected adsorbents using either NaC1 or the surfactants, Tween 80 and Triton X-100. In addition, the selective binding of LF from cheese whey and its subsequent elution from MicroCel with NaCl demonstrated that silica adsorbent materials could offer a low-cost, food-grade extraction process.
Using portable sawmills to produce high value timber from farm trees in the semi-arid zone

Blackwell, Philip A. (University of Melbourne, 2002)

There is a perception by some within the sawmilling industry that portable sawmills cannot produce the sawing quality in hard high-density timbers that is required to be merchantable in the manufacturing industry � especially the higher value sectors such as furniture. This study investigated the on-site processing of farm timbers from the semi arid regions of Australia using two different portable sawmills. There were a limited number of plantations with sufficient quantity of suitable saw logs within the low rainfall regions of south-eastern Australia for sawing trials. The only plantations that had sufficient saw logs were of high-density eucalypt species. The four species selected were Brown Mallet (Eucalyptus astringens), Sugar Gum (Eucalyptus cladocalyx), Yellow Gum (Eucalyptus leucoxylon) and Swamp Yate (Eucalyptus occidentalis). The portable sawmills selected for investigation were at the lower end of automation available on portable sawmills. Both mills required an operator to push and pull the power head along the log to produce sawn boards. The mills used in the sawing trials were a single circular blade type sawmill, which was represented by a `LucasMiIl� Model 8' and a horizontal bandsaw type sawmill, which was represented by a `Laidlaw� Farmill'. Initial results showed the selected species produced dimensionally consistent 150 mm wide boards that could be used in the manufacture of furniture or other products. The key criterion for investigation of sawing with both types of portable mill was the straightness of cut as the measure of sawing accuracy. This was measured with a modified straightedge and digital calipers. A total deviation or waviness in the cut of less than 1.5 mm was considered acceptable. An investigation using the single circular blade sawmill sawing with four different width blade tips revealed the 5 and 5.7 mm wide Carbide-tipped blades produced straighter cuts than the 4.5 and 5.4 mm wide Carbide-tipped blades in each of the trial species. The 5.0 mm blade also produced straight cuts with the fastest feed-speed in the majority of species while the 5.7 mm blade was the slowest sawing blade. The use of a 5.0 mm tip width blade on a single circular blade sawmill could be considered as the most versatile blade that is capable of producing more straight cuts and at the fastest feed-speed when sawing high-density hardwood species than other tip width blades. Investigation using the horizontal bandsaw sawmill and varying the blade parameters of hook angle, tooth set and blade tension showed the consistency in obtaining the blade tension was a major factor in accurate sawing. At low blade tension, the straightness of cut was adversely effected. The other variables revealed that at the widest tooth set the deviation along the cut increased with the faster feed-speed. The range of hook angles tested had no effect on cut straightness. It is possible that at higher hook angles problems might occur, as experience within the sawmilling sector suggests, but the range selected in this study, inadvertently, did not extend that far. Investigation of three blade types with different tip construction and at different widths revealed the 32 mm wide Bi-Metal blade was the best general blade over the range of species. Although this blade did not produce the straightest cuts in all the species the cuts were within the accepted tolerance of 1.5 mm. The carbon steel and Carbide-tipped blade did produce the straightest cuts in some species but were outside the acceptable range in other species. A final trial to assess controlled feed-speed required the horizontal bandsaw to be modified with the attachment of a variable power feed unit to the sawing carriage. This modification allowed the feed-speeds to be doubled in most species without any reduction in the straightness of cut. The production of quality timber is technically feasible using portable sawmills if the conditions and parameters of the blade, timber and mill are matched to meet the problems each log will demonstrate during the milling process.
Dairy farm employment and support for change

Nettle, Ruth. (University of Melbourne, 2001)

Changes in the Australian farming sector over the last few decades have included an increase in farm size, a greater emphasis on product quality, and attempts by farm managers to increase labour productivity and/or substitute labour with capital. New demands on managers and farming systems are emerging from these changes that express themselves as pressures for improved business performance. An important issue for individual farmers as they expand their farms has been that of labour. Farms are facing organisational change, structural change and social change. Increasingly, "farm management" does not just concern the technical and biological issues of production. People management, relationship building, coping with employment law and wages, are all components of the altered management regimes. The issues of labour and employment are most prevalent in the dairy industry, yet research in the area has tended to focus on the technical and economic challenges of production, broad patterns of rural labour markets or aggregated sociological analysis of employment trends. Most studies of labour and employment in agriculture have taken as "given" the social aspects of production. These approaches have informed, but not assisted the issues most keenly felt by farmers or the dairy industry. This thesis is concerned with defining the nature of dairy employment issues from the employer and employee perspectives with a view to the design of effective support and intervention in the employment domain. The research involved study of case farms in Gippsland, Victoria, which accounts for 27% of Australia's milk production. The methods used included in-depth interviews over time with case study dairy farm employers and employees, an action research group involving farm owners struggling with employment change on their farms, and interviews with people contributing to training and other aspects of labour in the dairy industry. These methods provided the data for analysis using a grounded theory approach (Glaser and Strauss, 1967) to explore social processes. Analysis of the nature of employment relationships provided a means of understanding change processes through time. This understanding is summarised in a conceptual model. Through the conceptual model, employers, employees and intervening third parties can see that the employment relationship itself is purposeful and not just functional in achieving farm, job or financial outcomes for participants. It is the different perspective that employer and employees bring to the relationship and the mutual involvement in relationship processes that appears to determine employment relationship outcomes. The thesis concludes that the employment relationship is central to an understanding of farmer and employee issues on farms, but that understanding cannot be gained from just the sum of the employer and employee perspectives. This means that employee and employer need a joint understanding of the fundamental relationship processes, and their role in these, if mutually favourable outcomes are to be achieved. Critical transition points in the change in emphasis from production management towards people management are also identified. Employers, employees and third parties can identify these critical transition points in advance to assist their adaptation in employment. Support in the area of farm employment relationships was seen to be lacking from current third party intervention, and correcting this deficiency may offer the best opportunity for improvement. A group intervention using action research provided insight into possible future support mechanisms, with a focus on learning rather than training. It is argued that there is a need for a widening of the focus of extension interventions to include human relationships and interaction for the employment realm. A collaborative learning platform involving interveners and employment relationship actors is seen as a way forward for a change in employment and extension (intervention) practice. The conceptualisation of farm employment and intervention is presented as a solid platform for future research and development.
Dairy farm employment and support for change

Nettle, Ruth. (University of Melbourne, 2001)

Changes in the Australian farming sector over the last few decades have included an increase in farm size, a greater emphasis on product quality, and attempts by farm managers to increase labour productivity and/or substitute labour with capital. New demands on managers and farming systems are emerging from these changes that express themselves as pressures for improved business performance. An important issue for individual farmers as they expand their farms has been that of labour. Farms are facing organisational change, structural change and social change. Increasingly, "farm management" does not just concern the technical and biological issues of production. People management, relationship building, coping with employment law and wages, are all components of the altered management regimes. The issues of labour and employment are most prevalent in the dairy industry, yet research in the area has tended to focus on the technical and economic challenges of production, broad patterns of rural labour markets or aggregated sociological analysis of employment trends. Most studies of labour and employment in agriculture have taken as "given" the social aspects of production. These approaches have informed, but not assisted the issues most keenly felt by farmers or the dairy industry. This thesis is concerned with defining the nature of dairy employment issues from the employer and employee perspectives with a view to the design of effective support and intervention in the employment domain. The research involved study of case farms in Gippsland, Victoria, which accounts for 27% of Australia's milk production. The methods used included in-depth interviews over time with case study dairy farm employers and employees, an action research group involving farm owners struggling with employment change on their farms, and interviews with people contributing to training and other aspects of labour in the dairy industry. These methods provided the data for analysis using a grounded theory approach (Glaser and Strauss, 1967) to explore social processes. Analysis of the nature of employment relationships provided a means of understanding change processes through time. This understanding is summarised in a conceptual model. Through the conceptual model, employers, employees and intervening third parties can see that the employment relationship itself is purposeful and not just functional in achieving farm, job or financial outcomes for participants. It is the different perspective that employer and employees bring to the relationship and the mutual involvement in relationship processes that appears to determine employment relationship outcomes. The thesis concludes that the employment relationship is central to an understanding of farmer and employee issues on farms, but that understanding cannot be gained from just the sum of the employer and employee perspectives. This means that employee and employer need a joint understanding of the fundamental relationship processes, and their role in these, if mutually favourable outcomes are to be achieved. Critical transition points in the change in emphasis from production management towards people management are also identified. Employers, employees and third parties can identify these critical transition points in advance to assist their adaptation in employment. Support in the area of farm employment relationships was seen to be lacking from current third party intervention, and correcting this deficiency may offer the best opportunity for improvement. A group intervention using action research provided insight into possible future support mechanisms, with a focus on learning rather than training. It is argued that there is a need for a widening of the focus of extension interventions to include human relationships and interaction for the employment realm. A collaborative learning platform involving interveners and employment relationship actors is seen as a way forward for a change in employment and extension (intervention) practice. The conceptualisation of farm employment and intervention is presented as a solid platform for future research and development.
A functional approach to stream buffer design in mountain ash forest

Dignan, Paul. (University of Melbourne, 2001)

Buffer strips, zones of vegetation retained along stream banks in, and adjacent to, logged areas, are used to maintain water quality and to protect a range of values pertaining to stream and riparian resources. They are commonly applied as strips of undisturbed forest of constant width from the stream, but their effectiveness varies with topographic, edaphic, vegetation and climatic factors. The use of variable buffer widths based on functional criteria has been proposed as a more rational basis for the design of stream buffers. The purpose of this thesis is to test the application of this approach to stream buffer design in the mountain ash forests of south-eastern Australia. It examines some of the main problems encountered in the design of stream buffers, namely temporal and spatial variation in the extent of soil saturation and overland flow, the deterioration of established buffers and the frequency and nature of unmanaged sediment flows into buffers. It also looks at the ability of buffers to maintain the light environment in riparian forest and develops a light penetration edge effects model for use in buffer design. Periodic field survey of a network of streams around a logged area found considerable variation in the spatial and temporal extent of surface soil saturation and overland flow, extending laterally up to 190 m from the main channel. Large areas of surface hydrological activity were particularly evident at the confluences of streams and towards the lower ends of the stream catchments. The deterioration of buffer vegetation was also highlighted as a factor to be considered when looking at effective buffer width. Eighteen percent of the buffers surveyed were found to be severely degraded and 69% of these were as a result of penetrating fire during broadcast slash burning. Where penetrating fire was not evident, edge aspect had the major influence on buffer overstorey crown health, with 33% of trees in north facing edges classed as severely degraded compared to 10%, 11% and 14% for south, east and west facing edges respectively. Catastrophic windthrow was evident where edges faced the direction of damaging winds. Maintenance of the light environment is an important ecological function of buffers in riparian forests. Measurements of the understorey light environment using hemispherical photographs were used to characterise the natural light regime in riparian and upslope forest. A matched set of post logging photographs were used to develop a model of the response of the light regime to edge creation. The natural understorey light environment around the streams was influenced by proximity to the streamline to about 50 m upslope, light penetration increasing on average at a relative rate of about 9% for every 10 m from the streamline to the upslope eucalypt forest. Light penetration was also strongly influenced by height above ground, with steeper gradients associated with lower order streams. Logging of the upslope forest resulted in major changes in light penetration close to the cut edge, reducing with distance into the forest. Distance from the cut edge was the main factor influencing light penetration edge effects, with most of the change occurring within 10-30 m of the edge. Manipulation of the edge orientation using the hemispherical images enabled models of the change in light penetration following edge creation to be developed for edges facing north, east and west, with distance from the edge as the only significant site factor. The importance of buffers for the control of unmanaged sediment flows from logged areas was examined by surveying 7 km of buffer edge to determine the frequency and nature of these flows. Seven instances of sediment flow into buffer were noted and all were due to the failure of in-coupe erosion control measures. This led to the conclusion that sediment control was a valuable function of buffers but it was not a suitable design criterion for multi-purpose buffers. The site specific empirical models of light penetration were combined with conceptual models developed in other forest types for Large Woody Debris (LWD) recruitment and stream bank stability to compare fixed width buffers with multi-purpose functional models in terms of resource use and the protection of stream and riparian zone values. Fixed width buffers of 20 m were inconsistent in the level of protection afforded to the light environment both in the vicinity of the stream and in the riparian zone. They generally provided about 60- 80% maintenance of LWD potential. Variable width buffers provided a consistent level of protection for both these functions, although the cost in terms of resource requirement was moderately high. The fixed width buffers occupied 13-22.5% of the available area compared to 31-37% for the variable width buffers. Measurement of the buffer from the outer edge of the riparian zone proved to be effective in increasing the level of maintenance of light in this zone for quite a small increase in the land area required.
A functional approach to stream buffer design in mountain ash forest

Dignan, Paul. (University of Melbourne, 2001)

Buffer strips, zones of vegetation retained along stream banks in, and adjacent to, logged areas, are used to maintain water quality and to protect a range of values pertaining to stream and riparian resources. They are commonly applied as strips of undisturbed forest of constant width from the stream, but their effectiveness varies with topographic, edaphic, vegetation and climatic factors. The use of variable buffer widths based on functional criteria has been proposed as a more rational basis for the design of stream buffers. The purpose of this thesis is to test the application of this approach to stream buffer design in the mountain ash forests of south-eastern Australia. It examines some of the main problems encountered in the design of stream buffers, namely temporal and spatial variation in the extent of soil saturation and overland flow, the deterioration of established buffers and the frequency and nature of unmanaged sediment flows into buffers. It also looks at the ability of buffers to maintain the light environment in riparian forest and develops a light penetration edge effects model for use in buffer design. Periodic field survey of a network of streams around a logged area found considerable variation in the spatial and temporal extent of surface soil saturation and overland flow, extending laterally up to 190 m from the main channel. Large areas of surface hydrological activity were particularly evident at the confluences of streams and towards the lower ends of the stream catchments. The deterioration of buffer vegetation was also highlighted as a factor to be considered when looking at effective buffer width. Eighteen percent of the buffers surveyed were found to be severely degraded and 69% of these were as a result of penetrating fire during broadcast slash burning. Where penetrating fire was not evident, edge aspect had the major influence on buffer overstorey crown health, with 33% of trees in north facing edges classed as severely degraded compared to 10%, 11% and 14% for south, east and west facing edges respectively. Catastrophic windthrow was evident where edges faced the direction of damaging winds. Maintenance of the light environment is an important ecological function of buffers in riparian forests. Measurements of the understorey light environment using hemispherical photographs were used to characterise the natural light regime in riparian and upslope forest. A matched set of post logging photographs were used to develop a model of the response of the light regime to edge creation. The natural understorey light environment around the streams was influenced by proximity to the streamline to about 50 m upslope, light penetration increasing on average at a relative rate of about 9% for every 10 m from the streamline to the upslope eucalypt forest. Light penetration was also strongly influenced by height above ground, with steeper gradients associated with lower order streams. Logging of the upslope forest resulted in major changes in light penetration close to the cut edge, reducing with distance into the forest. Distance from the cut edge was the main factor influencing light penetration edge effects, with most of the change occurring within 10-30 m of the edge. Manipulation of the edge orientation using the hemispherical images enabled models of the change in light penetration following edge creation to be developed for edges facing north, east and west, with distance from the edge as the only significant site factor. The importance of buffers for the control of unmanaged sediment flows from logged areas was examined by surveying 7 km of buffer edge to determine the frequency and nature of these flows. Seven instances of sediment flow into buffer were noted and all were due to the failure of in-coupe erosion control measures. This led to the conclusion that sediment control was a valuable function of buffers but it was not a suitable design criterion for multi-purpose buffers. The site specific empirical models of light penetration were combined with conceptual models developed in other forest types for Large Woody Debris (LWD) recruitment and stream bank stability to compare fixed width buffers with multi-purpose functional models in terms of resource use and the protection of stream and riparian zone values. Fixed width buffers of 20 m were inconsistent in the level of protection afforded to the light environment both in the vicinity of the stream and in the riparian zone. They generally provided about 60- 80% maintenance of LWD potential. Variable width buffers provided a consistent level of protection for both these functions, although the cost in terms of resource requirement was moderately high. The fixed width buffers occupied 13-22.5% of the available area compared to 31-37% for the variable width buffers. Measurement of the buffer from the outer edge of the riparian zone proved to be effective in increasing the level of maintenance of light in this zone for quite a small increase in the land area required.

School of Agriculture, Food and Ecosystem Sciences - Theses

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