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Research in the McGonigle
laboratory
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Mycological Studies Fungi on conifer seedlings at alpine treeline: Orchid conservation: mycorrhizal relations are under investigation for a local and rare ladies’ tresses species by 18S sequencing using fungal primers prepared in Idaho. Field sites are along the Snake River in the canyons of the South Fork. Initial attempts to isolate the orchid mycorrhizal fungus from root macerate prepared under sterile conditions used dilution plating to malt extract agar and yielded eight fungi from the Ascomycota, which I identified to species in the genera Myrothecium (2 species), Penicillium (2 species), Leptosphaeria, Graphium, Setosphaeria, and Paraphaeosphaeria. These fungi are not from taxa associated with orchid mycorrhizae, but nonetheless they offer an opportunity to evaluate, by sequence comparisons, the taxonomic distance between them and other isolates of the same and related species as available in the sequence database. Further isolations from a second batch of field-collected orchids were made by direct transfer of coarse macerate of root to modified Melin-Norkrans agar and successfully yielded multiple isolates of a single slow growing fungus that is very likely the orchid mycorrhizal fungus. Sequencing of this newly isolated fungus is in progress. Arbuscular mycorrhizae following fire in sagebrush steppe: I have recently found that mycorrhizal inoculum in soil is reduced significantly following fire in sagebrush steppe using replicated plots that were experimentally burned. To detect these effects, I took undisturbed cores from burned and not burned plots one year after the fire and conducted a bioassay for infection of test seedlings under greenhouse conditions. An addition treatment of sagebrush removal by chainsaw made at the time of the burn, but with no burning, was indistinguishable from the treatment that was not burned, indicating that shrub canopy removal by itself is not the mechanism of the effect. The reduction in mycorrhizal inoculum is in keeping with the post-fire emergence of species from non-mycorrhizal plant families, such as the Chenopodiaceae, which I have documented for these plots. Root fungi and negative feedback: Plants introduced to soil in which a previous generation of the same plant species were recently present are frequently found to have reduced vigor. Mechanisms of this negative feedback has been suggested to be a build up of pathogens, but may also occur when a degree of specificity exists for a given pairing of plant and mycorrhizal fungus in terms of either the quantity of fungus produced or the size of benefit to the plant. Negative feedback could proceed when a plant promotes the growth of a fungus that is more effective mutualistically for a second plant species. In this way, the first plant stimulates growth of the second plant relative to itself, promoting diversity. Experiments are in progress to test for feedback in bunchgrasses of Idaho. Nitrogen release from lichen crust: Mineral nitrogen could potentially be released and become available to plants and other organisms when processes such as trampling destroy desert lichens. The lichen Psora cerebriformis was collected from undisturbed plots in the sagebrush steppe on the Snake River Plain, disturbed and incubaedmoist in the laboratory. At 28 days, the lichen had released ammonium nitrogen equal to ten times the combined ammonium- and nitrate-nitrogen found in lichen free-soil from the open or below sagebrush canopy. This level of mineralization is striking, especially given that the photobiont of P. cerebriformis is the eukaryotic algal species. |