Atractiella rhizophila, sp. nov., an endorrhizal fungus isolated from the Populus root microbiome

ABSTRACT

Among fungi isolated from healthy root mycobiomes of Populus, we discovered a new endorrhizal fungal species belonging to the rust lineage Pucciniomycotina, described here as Atractiella rhizophila. We characterized this species by transmission electron microscopy (TEM), phylogenetic analysis, and plant bioassay experiments. Phylogenetic sequence analysis of isolates and available environmental and reference sequences indicates that this new species, A. rhizophila, has a broad geographic and host range. Atractiella rhizophila appears to be present in North America, Australia, Asia, and Africa and is associated with trees, orchids, and other agriculturally important species, including soybean, corn, and rice. Despite the large geographic and host range of this species sampling, A. rhizophila appears to have exceptionally low sequence variation within nuclear rDNA markers examined. With inoculation studies, we demonstrate that A. rhizophila is nonpathogenic, asymptomatically colonizes plant roots, and appears to foster plant growth and elevated photosynthesis rates.

KEYWORDS:

• Basidiomycete
• plant microbiome
• root endophyte
• sterile mycelium

Acknowledgments

This research was sponsored by the Genomic Science Program, US Department of Energy, Office of Science—Biological and Environmental Research, as part of the Plant Microbe Interfaces Scientific Focus Area (http://pmi.ornl.gov). Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the US Department of Energy under contract DE-AC05-00OR22725. G.B. acknowledges AgBioResearch and Michigan State University for support. The authors thank Kevin Le for assistance with the photosynthetic measurements and Connie Robertson of the Duke Herbarium for assistance with fungal curation.

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