Thesis (M.S.)--University of Wisconsin--Madison, 1970. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Presented as Thesis (Ph. D.)--University of Wisconsin--Madison, 1932. / Caption title. Reprinted from Phytopathology, vol. XXIII, no. 2 (Feb. 1933). Includes bibliographical references (leaves 153-154).

M.Sc. / Inducible defence responses in both a susceptible cotton cultivar ( Acala ) and a resistant cotton cultivar ( OR-19 ) in response to elicitors fromVerticillium dahliae were investigated. These oligosaccharin elicitors represent the heat solubilized, non-dialyzable fraction of the pathogen cell wall. This elicitorfraction consist of 6.57 % protein and 68 % carbohydrate and represent merely a discrete portion of the cell wall. Moreover, symptoms such as chlorosis and necrosis were induced by the elicitor in both cultivars, but the timing and magnitute of symptom development differed in that the symptoms occurred much faster and were more intense ( hypersensitive response) in the resistant cultivar. An effective elicitor concentration of 30 ug/ ml ( = 21 ug glucose equivalents) was determined and used throughout this study. Inducible defence responses i.e, the accumulation of PR-proteins and specifically activities of B-1,3-glucanase and chitinase were investigated in the intercellular environment as well as cellular extractions of both cultivars. An attempt was also made to analyse the expression of B-1 ,3-glucanase and chitinase genes at them RNA level ( level of transcription) and to correlate it to the determined levels of enzyme activities. Lignification as well as smaller plant metabolites i.e, sesquiterpenoid-phytoalexins relating to pathogenesis that are induced by the elicitor, were also investigated in both cultivars. In this study it is shown that differences are found between Acala and OR-19 and that some of these differences can be correlated to plant resistance. These differences found in the time studies ( intensity, time of response, qualitative and quantitative differences ) of the defence responses induced in both cultivars is discussed against the background of disease resistance.

D.Sc. (Biochemistry) / Please refer to full text to view abstract

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Forage legumes are particularly important in the Province of Quebec. In 1961, hay (grass and legumes) occupied 67% of the crop area and was worth $97,307,000. or 55·8% of the total value of field crops. Improved pastures, not included in the above figures, occupied over 2,000,000 acres (Anon, 1961). Since alfalfa, birdsfoot trefoil, red, alsike, and ladino clovers are dominant in this hay crop, their agricultural importance is apparent. This, together with the fact that alfalfa is a common rotation crop, led to the choice of this plant for study. [...]

Verticillium dahliae Kleb. causes Verticillium wilt in potato (Solanum tuberosum L.). Hormone signaling pathways are known to play a role in plant defense reactions. A gene expression analysis was performed on a susceptible and a moderately resistant (MR) cultivar of potato after inoculation with either a highly aggressive (HA) or a weakly aggressive (WA) isolate of V. dahliae. Genes related to the salicylic acid (SA), jasmonic acid/ethylene (JA/ET), and abscisic acid (ABA) pathways showed higher expression in the MR cultivar than the susceptible cultivar indicating that they may contribute to resistance. Additionally, a number of genes showed a delayed reaction in the susceptible cultivar and only in plants inoculated with the HA isolate of the pathogen. This trend was observed in genes related to the SA and JA/ET pathways. Overall, this research indicates that more than one hormone signaling pathway may contribute to the defense against V. dahliae by potato.