Thesis (Ph. D.)--University of Adelaide, Dept. of Plant Science, 1997? / Includes bibliographical references.

The present study was carried out to determine the mechanisms of biological control of <i>Fusarium oxysporum </i>f.sp. <i>lycopersici </i>by <i>Brevibacillus brevis </i>under greenhouse conditions.  Dual culture techniques demonstrated that <i>B. brevis </i>is capable of inhibiting the growth of fungal mycelium and germination of fungal spores due to excretion of antifungal metabolite(s) into the substrate, while reciprocal <i>in vitro </i>tests demonstrated no impacts of <i>F. oxysporum </i>f.sp. <i>lycopersici </i>metabolites on viability of <i>B. brevis.  </i>When live tomato roots were introduced into microcosms containing <i>F. oxysporum </i>f.sp. <i>lycopersici </i>and <i>B. brevis,</i> however, the fungal pathogen showed a competitive advantage over controls without <i>B. brevis </i>in terms of host colonisation.  The steroidal glycoalkaloid α-tomatine, extracted from tomato, inhibited conidiospore germination and growth of <i>Fusarium oxysporum </i>f.sp <i>lycopersici,</i> but had no detectable effects on viability of <i>B. brevis.</i> The effects of preinoculation of tomato (<i>Lycopersicon esculentum, </i>variety Moneymaker) roots with <i>B. brevis </i>in presence and absence of <i>F. oxysporum </i>f.sp. <i>lycopersici</i> on the induction of defence enzymes was examined.  Varying activities of phenylalanine ammonia lyase (PAL), peroxidases (POX) and chitinases were observed in different treatments at different time points, suggesting that the genes encoding these enzymes play a role in defence against Fusarium wilt.  Although no direct evidence of induction of these enzymes by <i>B. brevis </i>alone was observed, plants which were preinoculated with the bacterium showed enhanced induction of PAL, POX and chitinases at different time points following subsequent inoculation with <i>F. oxysporum </i>f.sp. <i>lycopersici.</i> Complex interactions between the tomato plant, <i>B. brevis </i>and <i>F. oxysporum </i>f.sp. <i>lycopersici </i>occurred and changed with time, as indicated by variations in metabolites at different sampling times.

Thesis (Ph. D.)--University of Adelaide, 1988. / Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 61-70).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1981. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 139-146).

This thesis concerns the initial events leading to the induction of the phytoalexin response in the Phaseolus vulgaris L. - Colletotrichum lindemuthianum L. host - pathogen interaction The phytoalexin response is an expression of the resistance of the host to further pathogen invasion. The visible expression of the phytoalexin response is hypersensitive necrosis. One of the initial events leading to the induction of the phytoalexin response is thought to be the induction of the first enzyme leading to the synthesis of phenylpropanoid phytoalexins, namely L-phenylalanine ammonia-lyase (PAL). Standard methods for determination of PAL activities were found to lead to measurements of both phenylalanine amino-transferase (PAT) and PAL activities together. Further, PAT was found to have a higher affinity for L-phenylalanine than PAL. An isotopic assay was devised for the accurate estimation of PAT and PAL activities separately using a specific inhibitor of PAT, L-aspartic acid. These experiments were carried out in a whole (intact) plant system. A rapidly isolated cell and protoplast system wa.s specially devised for isolation of the pathogen cell wall constituents responsible for the induction of the phytoalexin response. Special care was taken to minimise mechanical damage in these systems by optimising methods of purification, viability and intactness. The pathogen cell wall component responsible for the induction of the phytoalexin response was found to be an asialoglycoprotein.

No description available.

No description available.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: plant pathogen interactions; turnip crinkle virus. Includes bibliographical references (p. 59-61).

Includes bibliography.