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

Inaug.-diss.--Berlin. / Lebenslauf. "Thematisches verzeichnis der instrumentalkompositionen Friedrich Wilhelm Rusts": p. 3-18 (at end). "Kritik der quellen": p. 7-11.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1933. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--Washington State University, May 2006. / Includes bibliographical references.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2007. / Title from title screen (site viewed Oct. 10, 2007). PDF text: xii, 199 p. : ill. (some col.) UMI publication number: AAT 3258408. Includes bibliographical references. Also available in microfilm and microfiche formats.

1. The difficulties in separating the individual members of the Uromyces pisi group are outlined. 2. A review of the literature on rust fungi is given in which it is brought out that the major criteria for delimiting the species are (i) dimensions, wall thickness, number of germ pores and their distribution, for uredospores, (ii) dimensions, thickness of wall and pore cap, and wall sculpturing of the teleutospores, (iii) host specialisation, and (iv) length of life cycle. 3, 76 herbarium specimens along with the locally occurring member of the U. pisi group were examined from these stand-points, and the relative desoxy-ribose nucleic acid (D.F. A) content per nucleus of U. pisi. U. punctatus and U. loti was determined. 4. It was found that the species of the group could be separated by statistically analysing the spore measurements. Only U. jordianus could be separated by the number of germ pores of its uredospores, and both spore types of all the Species had approximately the same wall thickness. It is shown that the sculpturing of the teleutospore wall varies within each species and shows a gradation from a weakly punctate, to a definitely punctate-striate condition. A review of the literature on host specialisation and life cycle is given for each species, and a host list and synonym list has been compiled for each. From this review it is pointed out that, (1) it is difficult to separate certain of the species of the U. pisi group by host reaction and (ii) biological races exist in some of the heteroecious species. 6. Inoculation experiments were carried out with the locally occurring U. punctatue on Astragalus danicus, and it was found that the rust could infect 9 other species of Astragalus and one of Medicago. Attempts to geminate the teleutospores by various chemical stimulants failed with the exception of one teleutospore. Observation and experiment showed that U. punctatus could overwinter by means of uredospores. Inoculation experiments were carried out on the aecidial host, but no infection ensued after four years. It is concluded that U.punetatus at St, Andrew has lost the ability to infect the aecidial host and that this is due to, (i) the absence of the aecidia host over a period of years leading to adaptation to the uredo host, and (ii) various climatic factors. 7. Inoculation experiments carried out with the local specimens of U. pisi on Lathyrus pratensis and U. loti on Lotus corniculatus, showed that these rusts were narrowly specialised on their resptective hosts. Other closely related rusts which exist in the Hemi- form and are highly specialised with regard to host selection, are described and it is suggested that these rusts have probably arisen from specialised races of the heteroecious members of the group. 9. The ecology and geographical distribution of the group is discussed. The number of leguminous rusts in Britain is less than the number on the Continent. With the exception of U. pisi, heteroecism in the group is confined to Central and S. Europe. Outside this region the heteroecious species adopt the Hemi- form, and can overwinter in the uredo stage. In this condition they 'become more specialised. The number of possible British hosts is greater than the actual number parasitised, except. U. loti and U. laburni where the actual numbers are the same as the possible numbers of hosts. In considering these points it is suggested that the absence of the aecidial hosts from the region outside central S. Europe, has led to the species adopting the Hemi-form and becoming more specialised. Also in this region the climate is not favourable to the development of the aecidium. 10. It is suggested on this evidence, that the members of the group probably have a common ancestor.

The development of our knowledge of the metabolism, nutrition., and physiology of the rust fungi has been restricted because of our inability to grow these fungi in axenic culture. Most of the physiological and biochemical investigations on rust fungi have been limited to studies of the germination and development of germ tubes. It is not known, whether failure of the rusts to grow axenically is associated with a metabolic block in essential biochemical pathways. The uredial stage of an Australian isolate (ANZ 126-6, 7) of wheat stem rust was grown on a relatively simple medium. Successful in vitro growth was obtained on a medium containing Czapek's minerals, glucose and an organic nitrogen source viz. yeast extract, peptone or BSA. Vegetative growth producing a discrete colony appeared to be dependent upon high density seeding, when conventional dry seeding techniques were followed. When a spore suspension in gelatin was used for inoculation consistent, reproducible vegetative growth at low density seeding was obtained. Water spore suspensions failed to support any growth on the same series of media, under identical conditions. Sodium citrate, host extract, and host protein fractions in general inhibited growth whereas pectin increased the lag phase. Spore-like bodies were obtained inside the colony, which were devoid of any pigmentation. It is suggested that the combination of physical and chemical factors surrounding the germinating spore play an important role in the in vitro development of rust fungi. / Land and Food Systems, Faculty of / Graduate

Doctor of Philosophy / Department of Plant Pathology / Erick D. DeWolf / Stripe rust (caused by Puccinia striiformis f. sp. tritici) and leaf rust (caused by Puccinia triticina) are the top two diseases of winter wheat (Triticum aestivum) with a 20-year average yield loss of 4.9% in Kansas. Due to the significant yield losses caused by these diseases, the overall objective of this research was to identify environmental variables that favor stripe and leaf rust epidemics. The first objective was to verify the environmental conditions that favor P. triticina infections in an outdoor field environment. Wheat was inoculated with P. triticina and exposed to ambient weather conditions for 16 hours. Number of hours with temperature between 5 to 25°C and relative humidity >87% were highly correlated and predicted leaf rust infections with 89% accuracy. The results of this outdoor assay were used to develop variables to evaluate the association of environment with regional leaf rust epidemics. Before regional disease models can be developed for a forecast system, suitable predictors need to be identified. Objectives two and three of this research were to identify environmental variables associated with leaf rust and stripe rust epidemics and to evaluate these predictors in models. Mean yield loss on susceptible varieties was estimated for nine Kansas crop reporting districts (CRD’s). Monthly environmental variables were evaluated for association with stripe rust epidemics (>1% yield loss), leaf rust epidemics (>1% yield loss), severe stripe rust epidemics (>14% yield loss) and severe leaf rust epidemics (>7% yield loss) at the CRD scale. Stripe rust and leaf rust epidemics were both strongly associated with soil moisture conditions; however, the timing differed between these diseases. Stripe rust epidemics were associated with soil moisture in fall and winter, and leaf rust epidemics during winter and spring. Severe stripe rust and leaf rust epidemics were associated with favorable temperature (7 to 12°C) and temperature (15 to 20°C) with relative humidity (>87%) or precipitation in May using tree-based methods of classification, respectively. The preliminary models developed in this research could be coupled with disease observations and varietal resistance information to advise growers about the need for foliar fungicides against these rusts in Kansas winter wheat.

Crown rust, caused by the fungus Puccinia coronata, is a severe disease negatively impacting seed quality and yield in oat (Avena sativa). Host genetic resistance is the primary means for controlling this disease. The most extensive oat map contains nearly 2,500 genetic markers, many of which are restriction and amplified fragment length polymorphic (RFLP or AFLP) markers. However, the use of more abundant single nucleotide polymorphic (SNP) markers combined with diversity arrays technology (DArT) would be more advantageous for marker assisted breeding (MAB) and genome wide selection (GWS) applications due to the availability of high density genotyping technologies. The purpose of using this technology is to improve the competitiveness of oat by producing varieties with durable resistance to crown rust and desirable traits that will benefit oat growers in the U.S. Panels of winter and spring oat were evaluated for resistance to crown rust in four field environments in Texas, Louisiana, Minnesota, and North Dakota during a two-year study in 2010 and 2011. Plants representing 702 elite lines of oat were phenotyped for crown rust resistance and found to have highly diverse responses. The winter oat lines demonstrated the best crown rust resistance and are expected to yield the most QTL to be used in developing durable crown rust resistance. Heritability of crown rust resistance in this study ranged from 0.88 to 0.90 in spring and winter oats, respectively. Crown rust measurements were also found to be repeatable. Repeatability ranged from 0.56 to 0.88 at Castroville, TX in 2011 and 2010, respectively in spring oats and from 0.79 at St. Paul, MN in 2011 to 0.96 at Castroville, TX in 2010 in winter oats. Oat lines contributed by states along the Puccinia pathway in Texas, Louisiana, Minnesota, North Dakota, and Wisconsin on average exhibited the best crown rust resistance as compared to other areas in the country where spring and winter oat are grown. GGE biplot analysis indicated that Castroville, TX was the most representative and most ideal testing location. The above results are expected to increase knowledge of the genetic diversity of the oat germplasm, yield comprehensive genotyping and phenotyping information for North American oat breeding programs, and to promote further use of GWS and MAB for key traits regarding disease resistance in oat. Future work is to conclude the association mapping process by completing genotypic analysis.

Barley leaf rust (<I>Puccinia hordei</I> G. Otth) has been the cause of numerous and often devastating disease epidemics since the beginning of agriculture. Leaf rust is one of the most important diseases that affect barley (<I>Hordeum vulgare</I> L.) throughout the world. The pathogen <I>Puccinia hordei</I> is an obligate parasite. Symptoms of barley leaf rust may range from small chlorotic flecks to large pustules containing spores. Leaf rust epidemics reduce yields and grain quality. Deployment of resistant cultivars is one of the most effective and economical means of controlling barley leaf rust. Identification and incorporation of new and effective sources of resistance are crucial to the success of barley breeding programs. Two types of resistance have been identified. They are race-specific resistance and partial resistance. A hypersensitive reaction by the host to infection of <I>P. hordei</I> isolates lacking corresponding virulence genes is indicative of race-specific resistance that is controlled by major genes. Sixteen race-specific genes (R<I>ph</I>1 to R<I>ph</I>16) have been identified. Partial resistance is generally polygenic and is often more durable that race-specific resistance. The purpose of this research is to determine the inheritance of resistance to leaf rust in the barley experimental line VA 92-42-46, to identify the gene(s) conferring resistance, identify putative resistance related markers, and to map the gene(s) to one or more barley chromosomes using molecular markers. The Virginia barley line 92-42-46 was selected for this research project because it possesses resistance to <I>P. hordei</I> race 30, which has overcome resistance conferred by R<I>ph</I>7. Crosses were made between VA 92-42-46 and Moore, a susceptible cultivar to leaf rust. Inheritance studies were performed by screening F₂ progeny and F_2:3 families against race 8 and race 30 to determine the number of leaf rust resistance genes in VA 92-42-46. Allelism tests were performed to determine gene identity. A single dominant gene at the R<I>ph</I>5 locus or a tightly linked gene confers the resistance to P. hordei in VA 92-42-46. Two populations, 'Moore' X VA 92-42-46 and 'Bowman' X 'Magnif', were used in this study for mapping molecular markers to provide comparison and confirmation of results. 'Magnif' possesses the resistance gene R<I>ph</I>5. Bulked segregant analysis was used to identify polymorphic RFLP and SSR markers that were used for mapping in each population. Linkage analysis revealed that the R<I>ph</I>5 gene maps to barley chromosome 3 (3H) above the centromeric region in the 'Moore' X VA 92-42-46 population. These findings agree with previous research that identified linkage between R<I>ph</I>5 and R<I>ph</I>7 on chromosome 3. The results obtained in this study do not support previous research that had reported the resistance gene R<I>ph</I>5 was located on barley chromosome 7 (5H). Further research should be conducted to verify the results of this study using the 'Bowman' X 'Magnif' population. The markers screened in the region above the centromere region of barley chromosome 3 were monomorphic for the 'Bowman' X 'Magnif' population except for the marker MWG561. Therefore, additional markers above the centromere of barley chromosome 3 should be screened. / Master of Science