School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemStudies of Ascochyta rabiei in Australia( 2005)Ascochyta rabiei (teleomorph: Didymella rabiei) which causes ascochyta blight is the most serious disease of chickpea (Cicer arietinum) in Australia as it causes significant losses in crop yield and quality. Although A. rabiei is heterothallic and genetically diverse elsewhere in the world, a study carried out on Australian isolates collected between 1995 and 2000 identified only one mating type and a low level of genetic diversity within the Australian A. rabiei population. In 2002, ascospores of Didymella rabiei, the sexual state of A. rabiei, were trapped in a discharge chamber, from chickpea stubble naturally infected with ascochyta blight in Western Australia. Examination of the stubble revealed pseudothecia typical of Didymella rabiei. The reported presence of the teleomorph in Western Australia indicated that the second mating type had been introduced into Australia or that the pathogen was capable of a low level of homothallic compatibility, previously undetected. The aims of this research were, to undertake a new survey of Australian A. rabiei isolates, to test for the presence of the second mating type, to determine if there has been a change in the diversity of the Australian population and to investigate if pathogenic variability was displayed among isolates. Sixty-seven isolates collected from chickpea fields in South Australia, New South Wales, Queensland, Victoria and Western Australia during the 2003 cropping season were single spored and confirmed as A. rabiei using a PCR test. The isolates were typed for mating type using MAT gene specific PCR primers and compared with tester isolates from USA. This test revealed that all the 67 isolates belonged to mating type 2 (MAT 1-2), thus, the presence of mating type 1 (MAT 1-1) in Australia could not be confirmed. Sequence Tagged Micro Satellite (STMS) markers were used to examine the genetic diversity of the A. rabiei isolates. The isolates were assessed for allelic variation at 19 microsatellite loci, each of which amplified a single locus. Seven of the loci were polymorphic across all the 67 isolates, while the remaining twelve were monomorphic. Based on the allele profiles at the seven polymorphic loci, 19 distinct A. rabiei haplotypes were identified with a total of 33 alleles. One haplotype constituted 35.8 % of the population and was found in the collections from South Australia, New South Wales, Queensland and Victoria. Cluster analysis did not show a clear distinction between isolates based on the state from which they were collected. Polymorphism across the 19 microsatellite loci revealed a slight elevation in diversity in the 2003-2004 population (Ht = 0.07; compared to 0.02 in the 1995 to 2000 collection) and an increase in the number of haplotypes compared with that detected in the previous study of Australian isolates. To examine the pathogenic variability of the Australian population of A. rabiei, nine isolates were inoculated on five chickpea differentials, ranging from highly susceptible to resistant, under controlled conditions optimal for A. rabiei growth and infection. Eight of the isolates were virulent on the susceptible and intermediate chickpea cultivars but not the resistant cultivar and one isolate was only virulent on the susceptible cultivar. Based on these results the isolates were classified into two pathotype groups. The results obtained from the study of the population structure and the pathogenic variability of A. rabiei in Australia will enable the Australian chickpea breeders to understand the A. rabiei population better for formulating management and breeding strategies.
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ItemFarmers defining sustainability : the identification of the social, environmental and economic interactions in cashew nut production in Kenya( 2005)This paper presents the issues of social, economic and environmental sustainability influencing the rural growers' decision-making processes regarding cashew nut production in Kenya. By examining the delivery of the `triple bottom line' which incorporates the economic, environmental and social concerns that are considered by the farmers as they pursue their production goals, the triple bottom line thus takes household micro-level planning and makes it explicit. This study analyses household triple bottom line decision-making with regard to the continuation or abandonment of cashew nut production. Few studies investigate issues at the community and household level that constrain production, such as land and tree tenure systems, effects of a liberalized marketing and pricing system, changes in the gender division of labour and household decision making patterns. The methodology used included fieldwork which investigated 40 farms through individual interviews with land owners', eight field extension officers, research officers and secondary data sources and attendance at cashew nut African regional meeting. The paper discusses underlying reasons for the declining production levels by focusing on household choices so as to encourage a reconceptualisation of extension practice which integrates environmental and social benefits because the production mandate so far is generally associated with assumptions concerning the economic benefits (Beilin, Paine and Pryor, 2003). This forms the basis for enhancing both extension and policy in order to bring about change in the sustainable development of the cashew nut industry in Kenya.
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ItemPerceptions of ecoforestry in selected project sites in Papua New Guinea( 2005)Land and forest resources in Papua New Guinea are held under customary ownership by clans. But clans have participated little in decision-making processes in any major forest resource development projects, although these have often had major effects on their areas and lives. The decisions about industrial logging have been made mainly by the government and multinational logging companies - though royalties have been paid to clans for extraction of the timber. Past logging operations have provided some infra-structural benefits but have also led to many environmental and socio-economic problems that affect the livelihoods of rural people. In an attempt to halt the further spread of large-scale logging, and under pressure from the World Bank, the European Union Commission to PNG and the Government of Papua New Guinea entered into a bilateral agreement to initiate the Papua New Guinea Ecoforestry Program in 1995. This was to be implemented through the involvement of clans as the forest resource owners. This study explores the experiences and views of clan members in two ecoforestry projects in West New Britain Province. The aims of the study were to describe the ecoforestry program in general and the two project study sites, and then to explore clan members' perceptions of the ecoforestry approach being promoted, based on their experience. The study was conducted with a view to identifying ways of improving the effectiveness of ecoforestry development projects in Papua New Guinea. Two ecoforestry project sites were chosen as case studies. The main data collection techniques were in-depth interviews with clan members participating in the ecoforestry projects, and observations of activities. The qualitative data collected were analysed using elements of a 'grounded theory' approach, which involved transcription of interviews from PNG Pidgin/English to word processed files in English, then examining and coding the transcripts for main themes. From these themes theory was developed about the way clan people viewed ecoforestry, and the prospects for the future of the approach. Data from secondary sources were used in description of the sites, and in the analysis and interpretation of data from interviews. The findings revealed strong views among some respondents about their gains in mechanical and management skills through the ecoforestry projects, and also on problems of transparency in financial management of projects, the hard work involved in ecoforestry, and difficulties faced by their female members left at home alone. Other difficulties mentioned were those of maintaining equipment and of sourcing spares for machines and securing reliable markets. Despite the many negative views expressed on ecoforestry, there was quite wide acceptance that the approach had major potential advantages in terms of self-determination for clans, learning skills, employment and income, village infrastructure and environmental care of the forest - when compared to industrial logging. In the final chapter a Force Field Analysis is used as a framework to discuss the implications of the main finding - for future efforts in ecoforestry in PNG. In general, the clan members were reluctant to give definite views on the future prospects of ecoforestry after withdrawal of the supporting aid agency. In answer to questions on this topic they tended to express views on the need for certain types of support in the future, and other ways for overcoming the difficulties of the past. There was a general desire to be given the opportunity to continue with the ecoforestry approach, in the hope that there would be improvement in community participation, skills and hence in benefits to their clans and communities.
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ItemSpecies composition of improved dairy pastures in Bumthang, Bhutan( 2005)Multilocation studies of forage mixtures since 1970s identified white clover, cocksfoot, tall fescue and Italian ryegrass as appropriate pasture mixture for Bhutanese temperate environments. To date, there has been limited evidence on the long-term sustainability of these mixtures in farmer managed environments. Forty-one grazed pastures and fifty cut pastures were sampled in the elevation range of 2500-3500 m asl. Species composition was expressed in terms of tiller/growing point density of grass and legume species. Tiller core technique was used to measure plant densities. Soil samples were collected from depth profile of 5- 15cm. The dried soil samples were analysed for P, K, pH and texture. Dairy farmers were interviewed to obtain paddock histories and information on defoliation management. The tiller density of cocksfoot was higher in cut pastures though cocksfoot was negatively associated with cutting frequency. Cocksfoot was negatively associated with white clover and Italian ryegrass for both cut and grazed pastures. Soil pH was negatively associated with pasture age. Negative associations between K and pasture age was observed for both cut and grazed pastures. White clover was positively associated with P in grazed pastures. Italian ryegrass was positively associated with P, soil pH and moisture in grazed pastures. Available P was negatively associated with elevation. Cocksfoot abundance in cut pastures has been attributed to cocksfoot being a well adapted hay type species. The lower tiller density of cocksfoot in grazed pastures may be the consequence of continuous grazing without adequate rest period. White clover is positively associated with available P due to white clover being a well known plant that requires adequate levels of available P. The positive association between Italian ryegrass and pH has been explained by the greater availability of P with increasing pH. A decline in the levels of available K in older pastures was related to repeated defoliation without K inputs to replace the losses.
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ItemCardamom cultivation, livelihoods and biodiversity in a H'mong farming system in Northwest Vietnam( 2005)The recovery of the cardamom market in northwest Vietnam since the mid-1980s has seen many new groups of small farmers engage in the cultivation of this crop. A particular type of cardamom (Amomum tsao-ko) has a long history of cultivation by H'mong people in the Hoang Lien Mountains of northwest Vietnam. This thesis examined the implications of cardamom cultivation for H'mong livelihoods and forest biodiversity in those mountain farming systems, and explored options for improving farmer livelihoods through cultivation of this crop. Cardamom is in demand for both its aromatic and medicinal properties. It is providing a key source of income for H'mong ethnic farmers living at higher altitudes, people typically isolated from many other markets. The perennial crop requires partial shade and cool temperatures and for these reasons farmers utilize montane forest for its cultivation. These forests are also important for their biological diversity. Some cardamom cultivation practices (including tree felling to allow light to the crop) have been identified as having potentially negative effects on biodiversity. In this study a (partial) Farming Systems Research approach was adopted, which involved describing the farming systems at three (case study) villages, and identifying implications of cardamom cultivation for livelihoods and biodiversity at each site. Farmers were making transition from upland crops (rice and maize) to wet rice cultivation through the use of terraces to meet subsistence requirements, and had adopted cardamom as a cash crop despite the major labour inputs required in establishment. Extensive areas of forest and/or grassland on steep slopes dominated village sites. Cardamom was found to provide a key source of cash income for almost all farmers in the study area and had raised household income levels above the government-defined poverty level. Growers were committing significant labour resources over the initial five years of cardamom establishment, prior to receiving income. This labour on cardamom production competed with, but did not entirely replace, labour input towards improving subsistence income, i.e. establishing terraced fields for rice. Market uncertainty for cardamom presented some risk to small-scale farmers' livelihoods. If the cardamom market were to become flooded or depressed, the outcome would be a major setback for a large proportion of households, given the modest income from other cash crops and low total current incomes. Future inquiry aimed at better market understanding and ensuring stable income levels is recommended. Cardamom fields contained a higher number of plant species representative of montane forest, and in general much more favourable habitat for forest dwelling fauna than existed in alternative agricultural land-use types such as rice fields, upland fields or grassland. Tree cover was reduced by 25-50 per cent as a result of cardamom field establishment in forest, but there was no selective tree species removal. The lack of knowledge of the effect of forest thinning for cardamom cultivation on fauna habitat and animal movement means the abundance of some fauna species may be decling without our knowledge. However, farmers' involvement in cardamom growing ensured that forest would not be removed for other (less biologically diverse) types of land use. Farmers from certain villages have asserted de facto local use rights over particular areas of montane forest through their establishment of cardamom fields. As a result, some farmers had gained access to montane forest for cardamom cultivation - where they had no access to land previously. Research on cardamom production should focus on providing opportunities for farmers without access to montane forest, to grow cardamom in agroforestry systems on suitable land types near their villages. Farmers could be involved in `adaptation' trials aimed at developing new agroforestry systems using shade from planted tree species - as has been achieved in India and other regions. Such agroforestry systems on existing agricultural land may also make a positive contribution to forest biodiversity by increasing total vegetation.
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ItemImmobilized pectinase on chitin and its application in fruit juice processing( 2005)The application of immobilized pectinase in the fruit juice depectinization processes can improve productivity, control the extent of reaction, facilitate automation and continuous operation, eliminate the need for a downstream enzyme inactivation step and reduce the chance for contamination of the final product with the enzyme. The objectives of this study were to optimize the immobilization procedures of pectinase on chitin, to examine kinetic characteristics of immobilized pectinase and to test the application of immobilized pectinase in batch bioreactor and packed bed bioreactor systems. In order to obtain high immobilized pectinase activity and absorption yield, Plackett- Burman design was applied to initially screen ten factors and identify the significant ones which influence immobilized pectinase processing. A total of ten factors was studied, 4 factors at activated stage (F1-F4), 3 factors at adsorption stage (F5-F7), 3 factors at conjugated stage (F8-F10). The ten factors were 40% NaOH (w/v) solution immersing time (F1), during activated stage, pH value of buffer solution (F2), glutaraldehyde concentration (F3), polymerised degree of glutaraldehyde (F4), during the stage of adsorption, pH value of buffer (F5), pectinase concentration (F6), absorption time (F7), during the stage of conjugation, glutaraldehyde concentration (F8), polymerised degree of glutaraldehyde (F9), and conjugation time (F10). Experimental results indicated five variables as significant factors for further optimisation by using the second-order experimental design. The five factors were pH (F5), the pectinase concentration (F6), glutaraldehyde concentration (F8), polymerised degree of glutaraldehyde (F9), conjugation time (F10). Uniform design was selected as response surface methodology experimental design to further optimise five significant factors in immobilized pectinase processes. The immobilized processes including immobilized pectinase activities and immobilized yield were well described by the second-order models. The statistical analysis showed the optimum conditions for immobilization of pectinase on chitin. The maximum immobilized pectinase activity value (134.4 EU/g) was achieved using a combination of pectinase concentration 753.1 EU/ml, AR 35, glutaraldehyde concentration 0.5% (v/v), pH 6.5 and time 5 hours. The maximum absorption yield (20.6%) was achieved using a combination of pectinase concentration 282.4 EU/ml, AR 35.3, glutaraldehyde concentration 0.47% (v/v), pH 6.5 and time 5 hours. The kinetic parameters of immobilized pectinase on chitin were investigated. The kinetic constants of immobilized pectinases were found to be 2.87 (% w/v pectin) and 0.0447 (OD/min) for Km and Vmax, respectively. Optimum pH value was pH 5.5. The optimum temperature was 80C. Immobilized pectinase maintained its activity during storage at 4C for 6 months. Immobilized pectinase stability maintained 89% of initial enzyme activities under continuous application for 15 days. Applications of immobilized pectinase in a batch bioreactor and packed-bed bioreactor were investigated. In a batch bioreactor, five variables were juice pH, reaction time, temperature, pectin concentration of juice and amount of immobilized pectinase. Juice qualities were measured as viscosity, turbidity and % reduction of total pectin. Uniform design was used as experimental design. Well-fitted second order models were established. In a packed-bed bioreactor, four variables were juice pH, temperature, flow rate and pectin concentration of juice. Juice qualities were tested as turbidity and % reduction of total pectin. Small composite design was applied as experimental design. Well-fitted mathematical models were also established. These models provided tools to improve immobilized pectinase performance by adjusting operational parameters. These studies showed possible commercial application of immobilized pectinase in fruit juice processing. Further work could include improvement of immobilized pectinase stability and scale up of bioreactor to test industrial applicability of immobilized pectinase.
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