Submitted to: Fungal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2011
Publication Date: 11/9/2011
Citation: Baynes, M., Newcombe, G., Dixon, L., Castlebury, L., O Donnell, K. 2011. A novel plant-fungal mutualism associated with fire. Fungal Biology. 116:133-144. Interpretive Summary: Morels are a highly-prized edible fruiting bodies of fungi that develop in temperate and boreal forests following fire and other disturbances. They are not known to develop in dry places where trees do not grow. However, in this study two species of morels were isolated from dryland regions in the western United States. The fungi are associated with cheatgrass, an invasive plant that greatly increases the risk of fire. The morel isolates were identified using DNA sequence data and tested to determine their effects on the growth and reproduction of cheatgrass as well as the heat tolerance of their seeds. When inoculated with a specific strain of morel fungus, growth and reproduction of the cheatgrass was increased as was seed thermotolerance. This information will be useful by researchers and land managers in determining fire tolerance and potential growth of cheatgrass.
Technical Abstract: Morchella, the genus of true morels, produces highly-prized edible fruiting bodies in temperate and boreal forests following fire, and other disturbances. Morels are not known to fruit in regions too dry to support forest. This restriction to forest may also be linked to the facultatively mycorrhizal-like nature of tree-morel associations. Morels have never been observed fruiting in the vast, treeless parts of intermountain, western North America , that are now dominated by an alien annual grass, Bromus tectorum (cheatgrass). By producing highly flammable fine fuels, cheatgrass greatly increases fire frequency in these semi-arid ecosystems below higher-elevation forests . Morels and cheatgrass are among the leading examples of fire-adapted fungi and plants, respectively, yet they have never been ecologically linked due to their presumed lack of distributional overlap. In this study, isolates of Morchella were isolated from from five cheatgrass populations in three western states (ID, NM, and WA) and were identified as two M. elata phylotypes, Mel-6 and Mel-12, using three nuclear genes (translation elongation factor-1 alpha, DNA-dependent RNA polymerase II, and 28S ribosomal RNA). The effects of these isolates on cheatgrass fecundity, biomass and seed thermotolerance were investigated. Significant increases in fecundity and biomass were observed in plants inoculated with Mel-6 isolates. Thermotolerance also increased in seeds inoculated with Mel-6 isolates. Our discovery extends symbiont-based thermotolerance of plants to a diverse guild of fungi in a fire-adapted plant invader that is transforming western North America.