Alpine tundra ecosystems are characterized by harsh environmental conditions including a short growing season with temperatures below freezing, high solar radiation, soil erosion, and elevated nitrogen deposition caused by anthropogenic activity. Plants in the alpine tundra rely on endophytic and mycorrhizal fungi for acquisition of nutrients and protection. These plant-microbial interactions could play an important role in maintaining plant diversity in this ecosystem. The objectives of this study were to describe the dominant fungal taxa found in seeds of six dominant species of plants in the alpine tundra and evaluate their potential function using a cultivated plant as a model. Seeds were collected from a moist meadow in the alpine tundra at the Long Term Ecological Research Site in Niwot, Colorado. Species collected included Geum rossii, Erigeron simplex, Artemisia scopulorum, Deschampsia cespitosa, Polygonum bistortoides, and Trisetum spicatum. Fungal cultures were sequenced using the Internal Transcribed Spacer nrDNA and identified using BLASTN and phylogenetic analysis. Dominant orders included Pleosporales (26%) and Hypocreales (23%). A total of 54 fungal cultures were isolated from seeds consisting of 12 unique genera. Germination experiments using commercial corn seeds were conducted for each fungal species to determine potential mutualistic or pathogenic roles. Sixty-six percent of the endophytes tested were closely related to seed pathogens and had pathogenic activity affecting germination and causing root necrosis. The most common genus isolated was Alternaria, accounting for 25% of the isolates. Phylogenetic analysis indicated 2 unique clades of Cladosporium, all of which showed positive effects on seed germination and plant growth. The high number of pathogenic fungi found in this study suggests that seed- associated fungi could have a direct effect on community composition and seed recruitment.
|Commitee:||Jenkins, Sean, Musser, Richard|
|School:||Western Illinois University|
|School Location:||United States -- Illinois|
|Source:||MAI 55/03M(E), Masters Abstracts International|
|Keywords:||Alpine tundra, Niwot, Seed associated fungi|
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