Thesis (M. Phil.)--University of Queensland, 2002. / Includes bibliographical references.

In 1982-1983, naturally formed blight cankers, within a zone ranging from the ground to 183 cm on three grafted American chestnut trees, were inoculated with a mixture of four European (white), and six, pigmented hypovirulent strains of Cryphonectria parasitica. A total of 202 C. parasitica isolates were recovered from 49 cankers located outside of the inoculated zone. Ninety-five isolates (47%) were white and 107 (53%) were pigmented. Forty-eight vegetative compatibility groups were identified among 110 white isolates collected from this and previous studies. The ratio of VC groups to isolates tested (S/N), and Shannon diversity index were calculated to be 0.43 and 3.64 respectively. Of the 48 VC groups identified, 25 consisted of two or more isolates. These 25 groups were found to be vegetatively incompatible with all four of the original hypovirulent white inoculated strains, consisting of three VC groups, but were compatible with five of the 11 most common pigmented VC groups recovered from previous studies. These data provide evidence for spread of the original European hypoviruses (Cryphonectria hypovirus 1, CHV1) but not for spread of the original inoculated strains. Forty-five VC groups therefore represent the minimum number of "new" VC groups into which one or more of the original hypoviruses (CHV1) have spread. Single-spore colonies of the white isolates recovered from the 49 cankers were placed into four cultural morphology (CM) groups based on degree and pattern of pigmentation, and type of colony margin in culture. The two largest CM groups contained 37 (CM group 3) and 33 (CM group 1) isolates. Single-spore colonies from the original, white inoculated strain, EP-49, were classified to CM groups 3 and 1, while colonies of EP-51W were classified into CM group 1. The spatial pattern of white isolates within cankers was evaluated using a 7 x 7 lattice plot. Spatial pattern determination using the join-count statistics, described by Pielou, indicated that three of the four cankers containing white isolates had random patterns of white isolates. Vegetative compatibility tests of C. parasitica isolates in the two cankers sampled for spatial pattern indicated that the majority of both white and pigmented isolates in the cankers were within the same VC group for each canker. This was frequently the case even when pigmented and white isolates occurred in adjacent lattice cells. Isolates in each of the cankers identified to VC group had random patterns of the major VC groups (includes pigmented and white isolates). Using a double matrix statistical test, the spatial pattern of white VC groups among the 49 cankers was found to be aggregated (P=0.019), whereas the spatial pattern of white isolates was found to be random (P=0.325). The Lloyd's index of patchiness value for the pattern of white isolates in all cankers was 0.91. This value is just less than 1.0, which would indicate a random pattern. / Master of Science

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An attempt has been made in this study to analyze, examine, and investigate the efforts of the city of Beaumont, Texas, through its comprehensive plan and its planning process, to alleviate or combat the blighted areas of the city and to determine to what extent the comprehensive plan document has been implemented.

Stemphylium blight is a defoliating fungal disease caused by <i>Stemphylium botryosum</i>. It has become more prevalent in Saskatchewan. Although not much is known about the biology of the fungus, increasing lentil (Lens culinaris) yield losses of up 62% have been reported in Bangladesh and India. The infection of lentil by <i>S. botryosum</i> was investigated under a range of temperatures (5 to 30°C), wetness periods (0 to 48 h) and wetness periods interrupted by dry periods of 6 to 24 h. The experiments involved testing the impact of environmental conditions on germination of conidia on glass slides and stemphylium blight infection on lentil (cv. CDC Milestone). Generalised linear models and non-parametric tests were used to determine the effects of these factors on conidial germination and disease development. Infection levels increased with increasing temperature and wetness duration. A latent period of 48 h was observed at 25°C and 30°C under continuous wetness. The duration of the latent period increased with decreasing temperatures and decreasing wetness duration. <i>S. botryosum</i> required warm temperatures (above 25°C) and a minimum wetness period of 8 h for optimal disease development. Low levels of infection were observed within the first 2 h of incubation at 10°C and increased with longer wetting periods up to 48 h and temperatures up to 30°C. The pathogen could maintain infectivity during interrupted wetness periods despite its requirement for prolonged wetness periods. Infection levels were not significantly affected by interrupting dry periods of 6 to 24 h although long dry periods (24 h) combined with higher temperatures (30°C) resulted in a decrease in stemphylium blight severity. Germination studies on glass slides supported these findings. Response surface models were developed that provided a good fit for the response of conidial germination to temperature and wetness duration. The coefficients of determination for the regression of observed against predicted effects ranged from 0.88 to 0.97. The general additive model could also be used to predict stemphylium blight severity responses to temperature and wetness duration (scaled deviance = 1.04). However, that model tended to overestimate infection levels especially at lower temperatures. The coefficients of determination for the observed against predicted effects at 5 to 30ºC ranged from 0.77 to 0.92 for the general additive model.