A mutant mycelial colony of Ustilago hordei (Pers.) Lagerh.' was studied by light and electron microscopy to compare its general morphology with results obtained from earlier cytological studies. Its ultrastructure is also compared with that of other fungi. The results obtained from light microscopy generally agree with those from earlier work. Cells of the mycelia are very long, irregular in length, and contain numerous mitochondria and one to several nuclei. Electron microscopy reveals the walls of the mycelial cells to be single layered fibrillar structures. In apical regions all the characteristic organelles are present. The elongate mitochondria have plate-like cristae that lie parallel to the long axis of the mitochondri and the outer bounding membrane is often thicker than the inner one; these two features of the mitochondria are both unusual. Endoplasmic reticulum is sparse. Branch hyphae and septae are not present. In differentiated areas there is an increase in the number of vesicles and larger vacuoles. Mitochondria undergo rather unique changes whereby concentric lamellae are formed in a bulge of outer mitochondrial membrane. These concentric lamellae are engulfed by vacuoles in which the lamellae appear to be transformed into tubular bodies. At some point these vacuoles fuse with the plasma membrane and release their contents into the space between the plasma membrane and the cell wall. The vacuoles seem to act as lysosomes. Branch hyphae and septae are present. Degenerate regions are very vacuolated and contain many membranous structures. Few organelles are present. Mitochondria are distorted and their cristae swollen or absent. Dictyosomes and lomasomes are not present throughout the hyphae. / Science, Faculty of / Botany, Department of / Graduate

Pulsed-field gel electrophoresis (PFGE) of the strains representing the 14 races of U. hordei, the causal agent of covered smut on barley, revealed extensive polymorphism in chromosome length and number. The purpose of this study was to determine by two approaches the exact chromosome number for each U. hordei race, and to ascertain whether some strains are aneuploid, using two approaches. A telomere-specific repeat from Fusarium oxysporum was used as a probe onto Southern blots of restriction digests of individual chromosome bands to determine the number of chromosomes contained in each band. Nineteen to twenty-three chromosomes were identified in the strains representing the 14 races of U. hordei. To ascertain the number of chromosomes identified by the telomere-specific probe, chromosome-specific libraries were constructed and linkage groups were established by using chromosome-specific fragments as probes. The homologous chromosomes identified by these probes were typically monosomic with a maximum of 15 percent of variability, but cases of disomy were also observed in some strains. The second objective of this study was to analyze a filamentous mutant of U. hordei, designated fil1-1, that was isolated following heat-shock treatment. The filamentous phenotype is of interest, because it is believed to be involved in pathogenicity. U. hordei is a dimorphic fungus which has yeast like cells that are non pathogenic, while dikaryons produced upon mating are filamentous and pathogenic. Molecular characterization of the fil1-1 mutant showed that it has suffered a 50 kb deletion in a 940 kb chromosome. Genetical and physical analysis placed the fill mutation near the terminus of one arm of the 940 kb chromosome. The filamentous phenotype reverted to the sporidial wild type in presence of cyclic AMP. Biochemical analyses revealed that the intracellular level of cyclic AMP is three-fold lower in the mutant phenotype than in the wild type. These results indicate that cyclic AMP is an important determinant in fungal morphogenesis. / Graduation date: 1998

Thesis (Ph. D.)--University of Wisconsin--Madison, 1950. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 153-162).

Extracellular ribonuclease activity was detected in culture media of sporidial and mycelial cultures of Ustilago hordei. The RNase activity was maximal at pH 5.0, 6.5 and 8.0. The secretion of the RNase activity was a function of the cell density. Release of pH 4.5 and pH 7.5 activity was coincident. Enrichment of the simple glucose and salts medium delayed the initial secretion of activity. The presence of RNA in the medium did not enhance the amount of activity released. Furthermore, since the presence of RNA in the medium was not required for the release of the RNase activity into the medium, it is suggested the synthesis and secretion is a constitutive function. N-methyl-N'-nitro-N-nitrosoguanidine was used to produce auxotrophic strains. Selection methods for the detection of strains deficient in extracellular RNase activity are discussed. / Science, Faculty of / Botany, Department of / Graduate

Thesis (Ph. D.)--University of Wisconsin--Madison, 1952. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 24-27).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1940. / Typescript. Includes abstract and vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [64]-66).

Nutritional mutants of Ustilago hordel were used to demonstrate that parasexual recombination occurs within the host plant (Hordeum vulgare) prior to the production of teliospores. The nutritional mutants were also used to show that resistance of the newly-germinated seedling of H. vulgare to U. hordei and of subsequently formed tillers to infection was not correlated, and was probably not controlled by the same gene or genes. The application of gibberellic acid to H. vulgare was found to cause an increase in the overall tiller height of healthy plants by increasing the elongation of Internodal regions 0-1, 1-2, 2-3, and 3-4. There was no increased elongation of internodal regions 4-5 and 5-6. The healthy tillers of diseased plants showed no Internodal elongation when gibberellic acid was applied. Diseased tillers, which are usually shorter than healthy tillers, were also unaffected by the presence of gibberellic acid. The injection of both mating types of U. hordei into the young developing spike of a normally resistant strain of H. vulgare resulted in the production of diseased spikes. This would indicate that blockage to normal infection occurs at the time of seedling penetration, at the level of tiller primordia development, or at the time of spike primordia development. / Science, Faculty of / Botany, Department of / Graduate

Graduation date: 1991

The question investigated in this study was whether or not somatic recombination can occur in Ustilago hordei whilst it is in the parasitic phase on barley. The investigation was carried out in two parts. In the first and major part, barley seeds were inoculated artificially with mixtures of nutritionally deficient mutants of U. hordei. This was done in such a way that infection of the mature plants could only occur if at least one recombination event had taken place asexually, between at least two infective dikaryons, prior to teliospore formation. One smutted plant was found. Detailed analysis of the teliospores from this infection was carried out. The second part of the study was designed to demonstrate that more than one infective dikaryon can simultaneously occupy the host. Again, mixtures of nutritionally deficient mutants were used to inoculate barley seeds but this time so that the origin of teliospores from any infection could be traced back to the parental types in the infective dikaryon. It was concluded that somatic recombination can in fact occur whilst the fungus occupies the host tissue. / Medicine, Faculty of / Medical Genetics, Department of / Graduate

Genetic studies were carried out on the fungal parasite Ustilago hordei (Pers.) Lagerh. and on its host, Hordeum vulgave L. (cultivated barley). In these studies of the host-parasite relationship, special emphasis was placed on the genetic investigation of the pathogenicity. The thesis is divided into four parts. Part I deals with multial1 elism of genes for virulence (v-genes) in the parasite, and demonstrated that four different levels of virulence (obtained on the barley cultivar Trebi) are controlled by alternative alleles at a single genetic locus in the parasite. This is the first demonstrated example of a series of multiple alleles determining different levels of virulence. Part II concerns the identification and characterization of v-genes in U. hordei and of resistance genes (R-genes) in H. vulgave. Three v-genes (two of them new, one of them previously known) were identified. It was shown that the previously identified gene was expressed either as a dominant or a recessive, dependingoon the conditions under which it was tested, and that the newly-identified genes were both recessive. Cultures possessing the newly-discovered v-genes were used in identifying two new R-genes in the barley host. A study of interactions involving the newly discovered v- and R-genes led to the conclusion that these interactions have their basis in gene-for-gene relationships. Part III deals with the synthesis of a complex biotype of u. hordei possessing v-genes at two genetic loci. Disease reaction obtained with this complex biotype were compared both qualitatively and quantitatively with those obtained with the simpler, parental biotypes. In tests on certain cultivars the complex biotype produced either the same or higher levels of disease reaction. Because the new biotype has ah extended host range it is considered that under certain conditions it would be comparatively more fit than either of the parental biotypes from which it was derived. Part IV of the thesis concerns the effects of nutritional deficiency on the action of v-genes. Dikaryons which were homozygous for arg, ad or met were in all cases non-pathogenic; for those which were homozygous for pdx, pathogenicity was unaffected. For dikaryons which were heterozygous for one or more nutritional deficiences, pathogenicity was either unimpaired or reduced, depending on the combination (deficiency: virulence gene: host cultivar) which was tested. It was concluded that the specificity of pathogen biotypes was not determined by the availability or non-availability of specific nutritional factors. However, the effects were not entirely non-specific, since changes in levels of virulence were shown only in certain tests. / Science, Faculty of / Botany, Department of / Graduate