2018 ESA Annual Meeting (August 5 -- 10)

OOS 40-6 - Capacity of root endophytes to buffer dominant grass species against heat and drought

Friday, August 10, 2018: 9:50 AM
345, New Orleans Ernest N. Morial Convention Center
Jennifer Rudgers1, Andrea Porras-Alfaro2, Katy Beaven3, Katherine Anderson3, Samantha Fox4, Jose Herrera5, Y. Anny Chung6, Chris Reazin4, Dylan R. Kent1 and Ari Jumpponen7, (1)Department of Biology, University of New Mexico, Albuquerque, NM, (2)Department of Biological Sciences, Western Illinois University, Macomb, IL, (3)Biology, University of New Mexico, Albuquerque, NM, (4)Biology, Kansas State University, Manhattan, KS, (5)Provost, Mercy College, Dobbs Ferry, NY, (6)Wildland Resources, Utah State University, Logan, GA, (7)Department of Biology, Kansas State University, Manhattan, KS
Background/Question/Methods

Plant roots are commonly colonized by conidial or sterile Ascomycota, often with melanized (dark) and septate hyphae that grow inter- and intracellularly in roots. Several lines of evidence suggest a role for these root-associated fungi in resistance, tolerance, or resilience to abiotic stress. However, relative to other functional groups of microbial symbionts in plants, the biogeography and functional ecology of root-associated fungi has been little studied. Coupled predictions on the biogeography of plants and their rhizobiomes can improve understanding of future ecological responses to climate change, particularly in cases where microbial symbionts buffer hosts against drought or warming. First, we documented latitudinal patterns in the diversity, abundance, composition, and root colonization of fungal rhizobiomes in foundation grasses across the North American Great Plains. To identify fungal taxa that may ameliorate heat or drought stress, we evaluated the relative importance of climate, edaphic factors, geography, and host traits as correlates of rhizobiome composition. Second, we paired individual fungal isolates with one foundation grass species, Bouteloua gracilis, in greenhouse experiments that manipulated both heat (25, 30, 35, or 40C) and drought (12, 16, or 20% soil volumetric water content) in a full factorial design.

Results/Conclusions

From our survey of roots of five foundation grass species across 24 sites, we obtained a total of 20.7 million high quality ITS2 reads representing 7,608 fungal OTUs. The great majority of fungal sequences belonged to the phylum Ascomycota (70%), whereas 28% belonged to Basidiomycota. For most metrics of fungal diversity, composition and abundance, latitudinal gradients differed among host grass species (species × latitude interaction, P < 0.05). Significant latitudinal trends included poleward declines in fungal OTU diversity and richness for Andropogon gerardii, a poleward increase in fungal OTU evenness for Bouteloua dactyloides, and a latitudinal shift in fungal composition for Bouteloua gracilis. Greenhouse experiments along drought and heat gradients showed strongly positive to neutral effects of culturable root endophytes on plant biomass. The largest gains through fungal symbioses occurred at high (35C) temperatures, with up to 80% increases in plant biomass relative to controls (e.g., Periconia macrospinosa). Some isolates (e.g., Microdochium sp.) reduced plant biomass relative to controls, but only at the warmest (40C) temperature. Together these results indicate a functional role for root-associated Ascomycota in ameliorating climate stress and characterize biogeographic gradients in these associations that can help predict the potential for plant-fungal mismatches under future climates.