Thesis (M.S.)--University of Wisconsin -- La Crosse, 2006. / Includes bibliographical references (leaves 69-73)

Arbuscular mycorrhizal fungi (AMF) form a mutually beneficial symbiotic relationship with a majority of land plants through an exchange of nutrients. Despite the importance of AM symbiosis in agricultural and ecological settings, relatively little is known about how the fungal symbiont actively promotes symbiosis. To overcome a host’s immune response, plant pathogens secrete effector proteins that modify a host to suppress an immune response. Few effectors have been identified in AMF, as bioinformatics methods have failed to accurately predict their sequences. To successfully colonize a plant, AMF form structures called arbuscules within plant root cortical cells. Arbuscules are a primary site of nutrient exchange during AMF symbiosis. This work is built on the hypothesis that AMF produce effector proteins to promote symbiosis, and that arbuscules are a site of effector secretion. Using Rhizophagus irregularis, Glomus versiforme and Medicago truncatula this work applies a proteomics-based approach using a new biotechnology to identify fungal proteins secreted by AMF. This novel approach using proteomics and proximity labelling to identify proteins by mass spectrometry is the first time this system has been used to study the plant-AMF relationship. In this work, mass spectrometry identifies a total of 24 R. irregularis proteins and two G. versiforme proteins that are candidate effectors involved in the plant-AMF symbiosis.

Ericoid Mycorrhizal fungi have been shown to form symbiotic associations with Erious plants and increase nutrients uptake by the plant. The objective of this study was to assess the potential of two ericoid mycorrhizal isolates Oidiodendron maius and Pezizella ericae as potential sources of inoculant for rabbiteye blueberry (Vaccinium ashei) and to assess the variation in consistency and degree of ericoid mycorrhizal fungi colonization within rabbiteye blueberry (Vaccinium ashei). Field trials were conducted in 2012 in Verona, MS at the North Mississippi Research and Extension Center. In this study data was collected on fruit yield, leaf tissue nutrient concentration, leaf tissue nitrogen concentration, and percent colonization of root tissue. Ericoid mycorrhizal fungal isolates Oidiodendron maius and Pezizella ericae showed no influence on rabbiteye blueberry (Vaccinium ashei) during this study.

No description available.

Arbuscular mycorrhizal fungi (AMF) are widespread soil dwelling microorganisms that associate with plant hosts. AMF receive carbon from the host as a result of the mutualism, while the plant’s ability to acquire nutrients is enhanced by AMF. Additionally, AMF benefit their host in the form of pathogen protection. While it is known that increased AMF species richness positively correlates with aboveground plant productivity, the relationship between AMF diversity and pathogen protection is not well understood. In a growth chamber study, the plant host Leucanthemum vulgare, a non-native plant species in North America, was introduced to all combinations of three AMF species either in the presence or absence of the plant root pathogen Rhizoctonia solani. In the presence of the pathogen, the plant host increased its dependence on the AMF symbiosis. However, the richest AMF species assemblage did not provide the greatest pathogen protection. Understanding how diverse groups of AMF protect plants from pathogen attack provides insight into how plant communities are formed and structured. / NSERC

No description available.

No description available.

"June 2002" / Bibliography: leaves 179-194. / 194 leaves : ill. (col.), plates (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The overall aim of the research presented in this thesis was to determine if the growth and function of external hyphae of Arbuscular Mycorrhizal (AM) fungi is affected by changes in soil pore size. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil and Water, 2002

Numerous soils have been contaminated by radiocaesium (Cs) as a result of nuclear weapon testing and accidents at nuclear power-plant facilities. Management of the areas, which have been exposed to either intense or diffuse Cs pollution, has therefore become a major environmental concern. Strategies orientated toward the use of plants and microorganisms, or both in combination, have been proposed in the recent years as potential players in removing or stabilizing Cs in contaminated soils. Among these microorganisms, arbuscular mycorrhizal (AM) fungi are of particular interest due to their unique position at the soil/root interface and their recognized role in element transport and immobilization. In the recent years, contradictory results have been published on the impact of AM fungi on Cs accumulation by plants, failing to ascertain whether AM fungi could effectively transport this radionuclide to their host. Therefore, the objective of this work was to determine the role of AM fungi in plant Cs acquisition and accumulation. Using in vitro compartmented systems, we unambiguously demonstrated that AM fungi could transport Cs to their host, while its accumulation within the extraradical mycelium was rather limited. Our results also suggested that AM fungi could have an effect on Cs distribution within their host. Indeed, it appeared that AM fungi could potentially limit the translocation of Cs from roots to shoot. However, if the results obtained during this research project have shown that AM fungi could influence the acquisition and accumulation of Cs by plants, their capacity to take part in phytoremediation strategies remains questionable and would need additional investigations. In particular, attention should be focused on the mechanisms behind Cs transport by AM fungi, their influence on Cs root to shoot translocation and the subsequent validation of the findings obtained to in situ conditions.

The present study aimed to examine the effects of root colonization in tomato, Solanum lycopersicum L. cv. Moneymaker, by the arbuscular mycorrhizal (AM) fungus, Glomus intraradices Shenck and Smith, on alleviating salt stress. I postulated that AM symbiosis increases tomato plant performance to salt stress. Two greenhouse experiments were done according to a randomized factorial experimental design. The results showed a significantly higher level of AM root colonization that also occurred earlier in salt than non-salt treated plants. There were also positive interactions between root colonization levels and the alleviation of salt stress; these contributions resulted initially on higher root fresh mass (FM), later on shoot FM, and DM, and higher phosphorus and unchanged potassium concentrations in roots. The effects observed in salt-treated plants were significant when root colonization levels were significantly different than those observed in non-salt treated plants. This suggests a relationship between the level of root colonization and the alleviation of salt stress in plants. The attempt to use molecular techniques to detect early root colonization was quite successful in detecting the presence of G. intraradices in AM plants. However, it was not possible to detect the presence of the AM fungus as early as by classical root staining. This was observed presumably because sampling methods were different. In general, the results support the hypothesis that AM root colonization contributes to some extent to salt resistance of tomato plants.