No description available.

No description available.

No abstract available. / Thesis (M.Sc.)-University of Durban-Westville, 1989.

This study examined leaf area index (LAI) and relationships with corresponding tree growth, climate and soil characteristics across New Zealand forest plantations. The aim of this study was to determine if quick measures of projected leaf area across environmental gradients of New Zealand were an accurate indicator of site quality. Projected leaf areas of Pinus radiata D Don and Cupressus lusitanica Mills seedlings were measured using a Li-Cor LAI-2000 plant canopy analyser at 22 locations representing the soil and climatic diversity across New Zealand plantation forests. Seedlings planted at 40 000 stems per hectare were used to test treatment effects of fertiliser, site disturbance and species over a 4 year period. It was hypothesised that collected climate and soil information would explain differences in LAI development patterns across sites as the canopies approached site and seasonal maxima. Averaged across sites Cupressus lusitanica 7.28 (± 2.59 Std.) m2 m-2 had significantly (p = 0.0094) greater projected LAIs than Pinus radiata 6.47 (± 2.29) m2m-2. Maximum site LAI (LAImax) varied from 2.9 to 11.8 m2 m-2 for Pinus radiata and from 3.1 to 12.6 m2 m-2 for Cupressus lusitanica. LAImax of both species was significantly and positively correlated with vapour pressure deficit, soil carbon, nitrogen, phosphorous and CEC, but negatively with solar radiation, temperature and soil bulk density. A seasonal model of LAI across sites illustrated an 8.5% fluctuation in LAI of established canopies over the course of a year. Despite considerable variation in climate and soil characteristics across sites the combined effects of LAI at harvest and temperature were significantly correlated with site productivity (r2 = 0.84 and 0.76 for Pinus radiata and Cupressus lusitanica respectively). A national model of LAImax (r2 = 0.96) was proposed for Pinus radiata across climate and soil environments and the significance of LAImax as a component of site quality monitoring tools is discussed.

Genetic improvement of a number of crops including soybean (Glycine max L. [Merr]) has been associated with stay-green. Research on stay green genes has focused primarily on genes involved with photosynthesis and chlorophyll degradation. The current study explores the impact of a group of developmental genes, known as the E gene series, on the rate of soybean leaf senescence. The objective of this experiment was to determine the role of E-genes in the control of leaf senescence in soybean. The experiment was conducted in a split-plot design with three replications. The main plots were two photoperiods imposed following R1; i) natural day length (Amb) and ii) incandescent day length extension of 3 hours (Amb+3). The split plots were five E-gene near-isogenic lines (NILs), planted on different dates to obtain synchronous flowering. Phenology, photosynthesis, normalized difference vegetative index (NDVI) and fluorescence measurements were taken including, dark adapted photosynthetic efficiency (Fv/Fm), electron transport rate (ETR), and leaf chlorophyll concentration (SPAD). Leaf tissues were also analyzed for gene expression patterns among Harosoy isolines. Yield parameters like dry matter accumulation, harvest index and grain yields were recorded. The leaf net photosynthesis was more closely related to ETR than to SPAD values, suggesting that visual observation of stay-green may not be as effective in evaluating functional senescence as measurement of ETR. Cultivars with the dominant E1 allele maintained functional photosynthesis for longer, such that full senescence was delayed by 10-15 days in these cultivars. This phenomenon was observed under both photoperiod treatments and irrespective of the genetic background (Clark and Harosoy) in which the alleles appeared. Maintenance of functional photosynthesis by the E1 dominant allele can be attributed to maintenance of high ETR, and Fv/Fm, as well as delayed decline in leaf chlorophyll concentrations. Expression of senescence related genes were delayed in the isoline which had delayed leaf senescence phenotype. Consistent with the effect on leaf senescence, the dominant alleles also reduced the rate of phenological development, such that R5 occurred later in genotypes with dominant alleles and under the Amb+3 treatment. Cultivars with the dominant E1 allele under extended photoperiod treatment accumulated more biomass and had decreased apparent harvest index which caused no change in grain yields. The dominant E allele may delay leaf senescence directly or indirectly, through its delay of reproductive development.

主催：JST/CREST，Vrije University, ALTERRA, IBPC

Bibliography: leaves 218-232. / 232 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis investigates the resistance response of barley towards R. secalis by examining the in vitro interaction between various components of the apoplastic fluid and the fungus. / Thesis (Ph.D.)--Adelaide University, Dept. of Applied and Molecular Ecology, 2001

Fungi have been an important source for producing a wide range of secondary metabolites of widely differing chemical structures, as well as biological activities. Many of their metabolites now play a major role in pharmaceutical and agricultural industries. A number of fungi were isolated from soil and leaf litter collected from Arthur’s Pass, West Coast and Kaituna Valley using a particle filtration technique. Fungi were selected based on their unusual morphology or observed cytotoxicity and antimicrobial activity for large scale culture and extraction. A pale yellow compound was isolated from cytotoxic extracts from the culture of Aspergillus versicolor. This compound was identified as sterigmatocystin and the identity confirmed by UV profile and mass spectrometry. Five compounds were isolated from extracts prepared from two different species of Penicillium of which three were active against P388 cells (mycophenolic acid, cycloaspeptide A and mevastatin), one was active against dermatophytes (griseofulvin) and one was not active (3,4,6,8-tetrahydroxy-3-methyl-3,4-dihydroisocoumarin). Two compounds were isolated from extracts prepared from two different species of Phoma. A dark red compound was found to be novel and showed activity against P388 cells and Bacillus subtilis. A second compound also showing cytotoxicity was identified as the known compound phomenone. A further new compound was isolated from extracts of an identified dematiaceous fungus. This alkyl glucoside, however, was not bioactive.

Plantation eucalypts are a recent and rapidly growing industry in Australia, and will eventually replace the logging of old-growth forests. Over 40% of these plantations have been established in south-western Australia, where more than 160 000 ha of Eucalyptus globulus plantations now occur. In the early 1900’s, this species was widely planted as an exotic in South Africa, but succumbed to severe pest (Gonipterus sp.) and disease (Mycosphaerella sp.) problems. Similarly, in south-western Australia E. globulus is an exotic species, but with the additional threat that it is planted adjacent to indigenous eucalypts, which increases the possibility of pests and pathogens switching between closely related eucalypt hosts. Over the past ten years, there have been anecdotal reports of increasing levels of Mycosphaerella leaf disease (MLD) in E. globulus plantations in south-western Australia. This increase in disease level is of concern to the industry. To date there have been no comprehensive studies into the taxonomy, biogeography and population genetics of MLD in south-western Australia. This thesis investigated the impact of MLD in south-western Australia with a focus on its impact, taxonomy, biogeography and population genetics. It is the first study worldwide to quantify the relative impact of different Mycosphaerella species in a regional plantation estate. A survey of pest, disease and nutritional disorders (Chapter 2) found that MLD was the most severe and frequently occurring, single taxonomic health threat to 1 and 2-year-old E. globulus plantations in south-western Australia. For the first time, this survey identified and quantified the impact of pest and disease damage to E. globulus plantations in the region. There were differences in the disease levels between plantations and this was due to initial Mycosphaerella species composition and inoculum level, and local climatic conditions favourable for disease, rather than to the provenance planted or the nutritional status of the individual plantations. The survey for Mycosphaerella pathogens of eucalypts (Chapter 3) identified two new species of Mycosphaerella (M. ambiphylla and M. aurantia) and extended the known geographic range of eight other species (M. cryptica, M. gregaria, M. lateralis, M. marksii, M. mexicana , M. nubilosa, M. parva and M. suberosa). Of these: M. lateralis and M. mexicana were new records for Australia; and M. gregaria, M. nubilosa and M. parva were new records for Western Australia. A new anamorph, Phaeophloeospora ambiphylla was described and linked to M. ambiphylla. The occurrence of these new species and disease records in south-western Australia is significant for the plantation-eucalypt industry worldwide. The finding of two new species highlighted the need to quantify the disease impact of these on eucalypt plantations; and the extension of the range the remaining species raised important quarantine issues, concerned with the movement of plant material between regions and countries. The biogeographical investigation of Mycosphaerella (Chapter 4) identified that the most widespread and serious cause of MLD in south-western Australia is M. cryptica. In addition to occurring on the exotic E. globulus, it also occurs on two of the three important indigenous forestry eucalyptus species in this region. That is, on E. diversicolor, and E. marginata, but not on Corymbia calophylla. In terms of the plantation estate of E. globulus, however, M. nubilosa is the most widespread pathogen. The current study found that MLD on E. globulus is a complex of several different species, whereas, on E. diversicolor and E. marginata it is caused by only M. cryptica. Two species, M. cryptica and M. marksii were found commonly on adult E. globulus leaves. Although M. cryptica was the most frequent and serious cause of disease on adult leaves, M. marksii levels appear to be increasing and the future epidemiology of this pathogen should be closely monitored. There is some concern that these two MLD species could become an economically important problem on adult leaves of E. globulus. At present severe levels of MLD is significantly more common on juvenile than on adult foliage. The phylogenetic analysis (Chapter 5), based on ITS rDNA sequences from the present study and those obtained from GenBank accessions, found that Mycosphaerella is an assemblage of largely polyphyletic anamorph genera. Ten distinct clades emerged from the analysis. With the exception of the Dissoconium and the M. recutita clade, which comprised of two and one species respectively, none were comprised entirely of one anamorph genus alone. The anamorph genera represented were often dispersed across more than one clade, indicating that these anamorphs have arisen separately in different phylogenetic lineages. Cercospora, Stenella and Uwebraunia anamorphs each occurred in more than one separate clade. Although on the basis of rDNA sequence data Mycosphaerella appeared mostly monophyletic there was some evidence that the Mycosphaerella genus may be polyphyletic. This was particularly evident from the Dissoconium clade which grouped as closely to the outgroup Botryosphaeria taxon as it did with the remaining Mycosphaerella species. It was argued that a multi-gene phylogeny, which includes sequencing many species in other genera aligned with Mycosphaerella, is required in order to satisfactorily answer the question of whether Mycosphaerella is truly monophyletic. The phylogenetic analysis also showed that the taxonomy of Mycosphaerella based on ITS sequence data needs further clarification. Some species that are morphologically distinct, such as M. vespa and M. molleriana, shared identical ITS sequences. Other morphologically distinct species differed by as little as one or two nucleotides. Yet in other cases, the sequence variation amongst isolates from the same species differed substantially. Much of this variation in M. cryptica and other species was attributed to poorly edited sequences that had been lodged with GenBank. It was postulated that although a part of the remaining variation reflected the existence of cryptic species, some was likely to be genuine intra-species differences. It was concluded that further genes need to be sequenced, and more standardised cultural studies conducted in order to define species boundaries within Mycosphaerella. Based on the ITS rDNA sequence data, two different molecular methods for the identification of Mycosphaerella species from eucalypts were developed (Chapter 6). The first of these was a PCR-RFLP method that enabled the identification of Mycosphaerella species present on eucalypts in south-western Australia. A key is provided, which enabled the identification of species on a combination of PCR-RFLP DNA fragment migration patterns and a small number of morphological features. This key enables the identification of Mycosphaerella species more easily than keys that rely on morphological features alone. Therefore, this has made it easier for non-Mycosphaerella specialists to identify species from this genus. The second molecular method developed for the identification of Mycosphaerella species was that of primers that selectively amplify the DNA of M. cryptica and M. nubilosa, the two most important causes of MLD (Chapter 6). This will allow the rapid identification of these two species by non-specialists in Mycosphaerella taxonomy. The primers from the current study will also enable early diagnosis of the possible causal organism of MLD in a plantation. Once the use of these primers for amplifying DNA from leaf tissue has been optimised, they will also facilitate studies into the early infection process of M cryptica and M. nubilosa. For example, the presence of the pathogen may be detected prior to the appearance of symptoms. Studies may be conducted to determine the length of a hemi-biotrophic phase, and the extent of tissue colonisation both spatially and temporally, beyond the necrotic lesion in these two Mycosphaerella species. Previously, such studies have been hampered by the slow growth rate of these fungi in culture and the lack of media that would allow their selective isolation and detection by directly plating diseased and non-diseased host tissue. This study has clearly indicated that Mycosphaerella species are the major disease threat to E. globulus plantations in Western Australia. It has also shown that over the relatively short period of time of less than ten years the number of species recorded has increased from three to ten, and that disease severity has increased in plantations. It is therefore critical to continue the research on this genus in order to understand the biology, epidemiology and population genetics of this pathogen. This is necessary in order to inform tree selection and silvicultural practise that will minimise the future impact of MLD. This is particularly important if the industry moves towards clonal and hybrid forestry as has occurred elsewhere in the world. This study has laid the foundations for future research on this disease through the elucidation of the taxonomy of Mycosphaerella in south-western Australia and by providing some important molecular tools for its diagnosis and further study.

Members of the genus Hakea (Proteaceae) are sclerophyllous, evergreen perennial shrubs or small trees endemic to Australia, with 65% of species confined to the South-West Botanical Province (southwestern Australia). Southwestern Australian Hakea species possess two contrasting leaf morphologies (broad or terete leaves) and fire-related life forms (non-sprouting (fire-killed) or resprouting (fire-surviving)), with each species representing one of four leaf morphology-life form groups.Representative species within each group were studied to determine whether they display similar distribution and ecophysiological patterns at both the adult and seedling stages. The distribution of species within these groups was best based on averages and variations in annual temperature and rainfall. The highest percentage of terete leaved non-sprouters (25 species) occurred in areas of low-moderate rainfall with large annual temperature ranges, whereas terete leaved resprouters (14 species) displayed a patchy distribution. Broad leaved resprouters (28 species) dominated areas of strongly seasonal rainfall, with few species occurring in the drier regions. Broad leaved non-sprouters (33 species) were best represented in areas of low annual temperature. The distribution of non-sprouters/resprouters may be due to the effect of climatic factors on seedling recruitment and/or fire frequencies. Leaf morphology appears to have a more direct influence on species distribution, as broad leaves are favoured in regions of medium-high, seasonal rainfall (less stressful habitats) while terete leaves are better adapted to tolerate hot, dry environments.Terete leaves are either simple (needle-like) or 2-3 pronged, and, apart from their narrow width, are characterised by their greater leaf thickness (> 1 mm), smaller projected area and mass, higher leaf mass per area (a measure of sclerophylly) and a ++ / lower density than broad leaves. Broad leaves are much more variable in their shape. Increased leaf thickness and sclerophylly in terete leaves can be partially attributed to the presence of a central parenchyma core and increased palisade thickness. This core is surrounded a compact network of fibre-capped vascular bundles. Thickness and sclerophylly were good indicators of relative nutrient content in terete, but not broad leaves. Both leaf types have a thick cuticle (> 20 mu m) and sunken stomates, with terete leaves possessing a greater stomatal density than broad leaves. Broad leaves are bilateral and hence amphistomatous. Adult and seedling leaves (of a similar leaf type) differed in morphology, but not anatomy, with some species producing broad seedling leaves and terete adult leaves.Seedlings growing under optimal growth conditions (full sunlight, well watered) in pots showed no relationship between rate of growth and ecophysiology with respect to the four species groupings, although seedlings of non-sprouters and broad leaved species had higher transpiration and photosynthetic rates than seedlings of resprouters and terete leaved species respectively. In response to high air temperatures (> 35°C), leaf temperatures close to or lower than the surrounding air temperature only occurred for terete leaved species possessing small individual and total leaf areas. By maintaining leaf photosynthesis rates during periods of relatively high air temperatures, terete leaved seedlings were able to produce more biomass per leaf area while retaining a low leaf area per seedling mass. When subjected to periods of water stress (withholding water), differences in water relations were most evident between seedlings of non-sprouters and resprouters, with resprouter seedlings showing an ability to minimise the decrease in relative water content for a given decrease in XPP. ++ / Although terete leaves possess many xeromorphic attributes, terete leaved seedlings were not necessarily superior at avoiding/tolerating drought. Terete leaves in seedlings may have alternative heat dissipation and/or anti-herbivore properties.Seasonal water relations of adult plants were monitored for over a year, including a period of prolonged summer drought at four sites (two on laterite (rocky substrate) and two on deep sand). The eight species inhabiting the lateritic sites were more stressed (more negative xylem pressure potentials (XPP)) in summer than the eight species on sandy soils, with lower conductances and higher leaf specific resistivity (XPP/area-based transpiration, LSR). Broad leaved species had higher transpiration rates and LSR, and more negative midday XPP throughout the study than terete leaved species. When spring (predrought) and summer (drought) data were compared, non-sprouters had lower XPP in summer, and lower transpiration rates and conductances in both seasons than resprouters. Non-sprouters on lateritic sites had the lowest water relations values in summer (drought tolerators). There was a tendency for broad leaved resprouters on sandy soils to have higher summer water relations values (drought avoiders). Broad leaved non-sprouters on lateritic soils could be considered the most water stressed group, with substantial plant death during the summer period. Terete leaved species on sandy soils were the most conservative in their water usage.