Thesis (Ph. D.)--University of Wisconsin--Madison, 1925. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 40-42).

Diss.--Universität von Münster, 1999. / Bibliogr. p. 86-100.

Fusarium head blight (FHB) is an important disease of wheat and other small grain cereals. The principal pathogen associated with FHB in Manitoba is Gibberella zeae (Schwein.) Petch (anamorph = Fusarium graminearum Schwabe). Currently there no biological control agents registered for the control of FHB. The overall objects of the project were to identify isolates that may be used in the biological control of FHB and to investigate the interaction between the identified biocontrol agents and G. zeae.In this study, 150 bacteria and 29 fungi were isolated from soil, wheat heads and crop debris from southern Manitoba. An additional 10 isolates of Trichoderma harzianum were obtained from the Canadian Collection of Fungal Cultures, CCFC (Ottawa, Ontario). The T. harzianum isolate, T-22 (RootShield) was included as a positive control. All were screened for inhibition of Gibberella zeae using confrontation plate assays in vitro and seed, wheat head, and straw assays in planta. Only 6% of bacterial and 45% of fungal isolates tested in the confrontation plate assays. Of the 6% of the bacterial isolates none significantly reduced FHB disease on wheat heads or reduced perithecial production on wheat straw, and had a negative effect on seed germination, therefore were not further evaluated. Chrysosporium sp. and Penicillium spp. and Trichoderma harzianum, were the fungal species that inhibited the growth of G. zeae by more than 50%. Of which Trichoderma isolates were the most effective and were able to over-grow G. zeae. Fourteen of the 18 isolates tested, including six Trichoderma and two Chrysosporium isolates, significantly reduced perithecial production on wheat straw by 52-89% compared to the control. From this study, Trichoderma harzianum was identified as most potentially effective candidate for the biocontrol of Gibberella zeae. Spore suspensions and cell-free filtrates of Trichoderma harzianum isolates were evaluated for their effectiveness in reducing perithecial and ascospore production of Gibberella zeae on wheat straw. Five T. harzianum isolates, including T-22 (RootShieldTM), reduced perithecial formation by 70% or more. Perithecial reduction was highest (96-99%) when T. harzianum spore suspension or cell-free filtrate was applied to straw 24 hours prior to inoculation with G. zeae. Control was less effective when T. harzianum was applied at the same time (co-inoculated) or 24 hours after G. zeae. Field trials showed significant reduction of perithecia on residues treated with T. harzianum prior to placement on the soil surface. Identification of those compounds in the cell-free filtrate most likely to affect biocontrol was accomplished through the use of cluster analysis, ordination and regression methods. It was found that isolates that produce similar levels of biocontrol had similar chemical composition. Ultrastructural changes were observed primarily in the exterior cells of the outer cell wall. Cytoplasmic degradation, invagination of the plasma cell membrane and thin cell walls were observed in the treated samples. Immature perithecia were overgrown by T. harzianum 15 days after co-inoculation. Few perithecia were overgrown at later stages. The perithecia affected by T. harzianum collapsed 21 days after inoculation (dai), compared to the perithecia in the untreated samples which collapsed 28 dai.

Fusarium head blight (FHB) is an important disease of wheat and other small grain cereals. The principal pathogen associated with FHB in Manitoba is Gibberella zeae (Schwein.) Petch (anamorph = Fusarium graminearum Schwabe). Currently there no biological control agents registered for the control of FHB. The overall objects of the project were to identify isolates that may be used in the biological control of FHB and to investigate the interaction between the identified biocontrol agents and G. zeae.In this study, 150 bacteria and 29 fungi were isolated from soil, wheat heads and crop debris from southern Manitoba. An additional 10 isolates of Trichoderma harzianum were obtained from the Canadian Collection of Fungal Cultures, CCFC (Ottawa, Ontario). The T. harzianum isolate, T-22 (RootShield) was included as a positive control. All were screened for inhibition of Gibberella zeae using confrontation plate assays in vitro and seed, wheat head, and straw assays in planta. Only 6% of bacterial and 45% of fungal isolates tested in the confrontation plate assays. Of the 6% of the bacterial isolates none significantly reduced FHB disease on wheat heads or reduced perithecial production on wheat straw, and had a negative effect on seed germination, therefore were not further evaluated. Chrysosporium sp. and Penicillium spp. and Trichoderma harzianum, were the fungal species that inhibited the growth of G. zeae by more than 50%. Of which Trichoderma isolates were the most effective and were able to over-grow G. zeae. Fourteen of the 18 isolates tested, including six Trichoderma and two Chrysosporium isolates, significantly reduced perithecial production on wheat straw by 52-89% compared to the control. From this study, Trichoderma harzianum was identified as most potentially effective candidate for the biocontrol of Gibberella zeae. Spore suspensions and cell-free filtrates of Trichoderma harzianum isolates were evaluated for their effectiveness in reducing perithecial and ascospore production of Gibberella zeae on wheat straw. Five T. harzianum isolates, including T-22 (RootShieldTM), reduced perithecial formation by 70% or more. Perithecial reduction was highest (96-99%) when T. harzianum spore suspension or cell-free filtrate was applied to straw 24 hours prior to inoculation with G. zeae. Control was less effective when T. harzianum was applied at the same time (co-inoculated) or 24 hours after G. zeae. Field trials showed significant reduction of perithecia on residues treated with T. harzianum prior to placement on the soil surface. Identification of those compounds in the cell-free filtrate most likely to affect biocontrol was accomplished through the use of cluster analysis, ordination and regression methods. It was found that isolates that produce similar levels of biocontrol had similar chemical composition. Ultrastructural changes were observed primarily in the exterior cells of the outer cell wall. Cytoplasmic degradation, invagination of the plasma cell membrane and thin cell walls were observed in the treated samples. Immature perithecia were overgrown by T. harzianum 15 days after co-inoculation. Few perithecia were overgrown at later stages. The perithecia affected by T. harzianum collapsed 21 days after inoculation (dai), compared to the perithecia in the untreated samples which collapsed 28 dai.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Abstracted in Dissertation abstracts, v. 19 (1959) no. 7, p. 1535-1536. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 101-103).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1939. / Typescript. Includes abstract and vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1928. / With this is bound an abstract. Reprinted from the Journal of agricultural research, v.43, October, 1931, p. 569-596. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Doctora en Bioquímica / Las giberelinas (GAs) son fitohormonas diterpénicas sintetizadas como metabolitos secundarios por algunos hongos, entre ellos Fusarium fujikuroi, patógeno del arroz que produce grandes cantidades de ácido giberélico (GA3). Esta especie forma parte del complejo taxonómico Gibberella fujikuroi que incluye otras 10 especies relacionadas filogenéticamente denominadas poblaciones de apareamiento (A-K). Aunque todas las especies del complejo G. fujikuroi contienen genes de la biosíntesis de GAs la producción de estos diterpenos se ha descrito casi exclusivamente en F. fujikuroi, con excepción de dos cepas de Fusarium proliferatum y una cepa de Fusarium konzum que sintetiza muy bajas cantidades de GAs. Con el objeto de investigar si existen otras especies productoras de GAs en el complejo G. fujikuroi, se caracterizaron varias cepas de Fusarium sacchari (aislado de la caña de azúcar), de Fusarium konzum (aislado de pastos de praderas) y de Fusarium subglutinans (aislado del maíz). F. sacchari es una especie cercanamente relacionada con F. fujikuroi, agrupada en el clado Asiático del complejo en tanto que F. konzum y F. subglutinans son especies filogenéticamente alejadas de F. fujikuroi agrupadas en el clado Americano. Las cepas de F. sacchari investigadas presentaron diferencias con respecto a su capacidad de sintetizar GAs. Cinco aislados (B-12756; B-1732, B-7610, B- 1721 and B-1797) resultaron activos sintetizando principalmente GA3 (2,76-28,4 mg/mL) mientras que otros dos (B-3828 and B-1725) resultaron inactivos. Las etapas catalizadas por la geranilgeranil difosfato sintasa (GGS2) y/o la ent-kaureno sintasa (CPS/KS) son limitantes en las cepas productoras ya que los niveles de GA3 aumentaron 2,9 veces por complementación con los genes ggs2 y cps/ks de F. fujikuroi. Con respecto a F. konzum, de los seis aislados que se investigaron tres (I-10653; I-11616; I-11893) sintetizaron GAs, principalmente GA1, un producto final diferente al de las cepas activas de F. sacchari. Además, los niveles de GAs sintetizados por F. konzum fueron muy bajos (menos de 0,1 mg/mL). Tres cepas de F. konzum resultaron inactivas y no presentaron actividad de ninguna oxidasa de GAs lo que sugiere que los genes respectivos no se expresan. Las dos cepas de F. subglutinans ensayadas no sintetizan GAs ni presentan actividad de las oxidasas. Estos resultados indican que la capacidad de sintetizar GAs está presente en otras especies del complejo G. fujikuroi además de F. fujikuroi, pero puede diferir significativamente entre cepas. Finalmente se investigó la biosíntesis de GAs en un conjunto de 19 cepas híbridas (CxD) provenientes de un cruce entre F. fujikuroi y F. proliferatum, dos especies muy cercanas filogenéticamente agrupadas en el clado Asiático del complejo G. fujikuroi. Las dos cepas parentales (F. fujikuroi C-1995 y F. proliferatum D-4854) contienen los genes de la biosíntesis de GAs pero difieren en su capacidad biosintética: C-1995 sintetiza GAs, principalmente GA3, mientras que D-4854 no produce GAs. Las cepas híbridas no presentaron un patrón de segregación Mendeliano 1:1 como se esperaba sino que se encontró en la progenie un patrón de tres fenotipos: 8 híbridos producen GA3 en cantidades similares a la cepa parental C-1995 en tanto que 6 cepas resultaron inactivas para la biosíntesis de GAs. Además de los fenotipos parentales una parte de la progenie (5 cepas) produjo pequeñas cantidades de GAs, principalmente GA1 y presenta bajos niveles de expresión de los genes. Estos resultados evidencian que el cruce interespecies puede generar nuevos patrones de metabolitos secundarios, en este caso de GAs. El conjunto de resultados obtenidos sugiere que la capacidad de sintetizar GAs en niveles significativos estaría restringida a las especies de Fusarium agrupadas en el clado Asiático del complejo G. fujikuroi / Gibberellins (GAs) are diterpene phytohormones synthesized as secondary metabolites by some fungi like Fusarium fujikuroi, a plant pathogen that produces high levels of gibberellic acid (GA3). This Fusarium species belongs to Gibberella fujikuroi, a taxonomic species complex that includes 10 other phylogenetically related species denominated mating populations (A-K). Even when all the species within the G. fujikuroi complex contain GA biosynthesis genes, the production of these diterpenes has been almost exclusively found in F. fujikuroi, except for two Fusarium proliferatum strains and one Fusarium konzum isolate that synthesizes very low GA levels. In order to find out if other species within the G. fujikuroi complex synthesize GAs, several strains of three Fusarium species were characterized: Fusarium sacchari (isolated from sugar cane), F. konzum (isolated from prairie grasses) and Fusarium subglutinans (isolated from maize). F. sacchari is closely related to F. fujikuroi and grouped in the Asian clade of the complex while F. konzum and F. subglutinans are phylogenetically distant species grouped in the American clade. Analyzed F. sacchari strains differed in their ability to synthesize GAs. Five isolates (B-12756; B-1732, B- 7610, B-1721 and B-1797) were active and synthesized mainly GA3 (2,76-28,4 mg/mL) while two others (B-3828 and B-1725) were inactive. The steps catalyzed by geranylgeranyl diphosphate synthase (GGS2) and/or ent-kaurene synthase (CPS/KS) were limiting in F. sacchari active strains since it was found that GA3 levels increased by 2.9 fold upon complementation with ggs2 and cps/ks genes from F. fujikuroi. For F. konzum, six isolates were analyzed of which three (I-10653; I-11616; I- 11893) synthesized GAs, mainly GA1, a different final product than that synthesized by F. sacchari active strains. GA levels formed by F. konzum isolates were very low (less than 0,1 mg/mL). Three F. konzum strains were inactive in GA biosynthesis and contained no GA oxidase activities suggesting that the respective genes were not expressed. For F. subglutinans the two isolates assayed did not synthesize GAs and lacked activity of the GA oxidases. These results evidence that GA biosynthesis is present in other species within the G. fujikuroi complex besides F. fujikuroi but may differ significantly between isolates. Finally, GA biosynthesis was investigated in a group of 19 hybrid strains (CxD) from an interspecies cross between F. fujikuroi y F. proliferatum, two closely related species that belong to the American clade in the G. fujikuroi complex. Both parental strains (F. fujikuroi C-1995 and F. proliferatum D-4854) contain the GA biosynthetic genes but differed in their ability to produce GAs: C-1995 synthesizes GAs, mainly GA3, while D-4854 did not produce GAs. The hybrid strains did not show a Mendelian 1:1 segregation pattern as expected but we found in the progeny a three phenotype pattern: 8 CxD hybrids produced GA3 at similar levels than the parental strain C-1995 while 6 strains were inactive for GA biosynthesis. Besides the parental phenotypes 5 progeny strains produced low GA levels, mainly GA1 and showed low expression of the respective genes. These findings indicate that interspecies crosses may generate new profiles of secondary metabolites, like the GAs. Altogether obtained results suggest that GA biosynthesis at significant levels would be restricted to the Fusarium species of the Asian clade in the G. fujikuroi complex / FONDECYT; FONDAP; MECESUP

No description available.

Zugl.: Hohenheim, Univ., Diss., 2008