Darksidea phi, sp. nov., a dark septate root-associated fungus in foundation grasses in North American Great Plains

ABSTRACT

Darksidea is a common genus of dark septate fungi—a group of ascomycetes in semiarid regions. A survey reported D. alpha and a distinct Darksidea lineage as abundant root-associated fungi of foundational grasses in North America. Fungi were isolated, and metabarcode data were obtained from sequencing of fungal communities of grass roots in the United States. During a comprehensive investigation of the Darksidea lineage, we carried out polyphasic taxonomy, genomic characterization, and identification of host associations, geographic distribution, and environmental factors that correlate with its abundance. For molecular phylogenetic studies, seven loci were sequenced. Isolates of the distinct Darksidea had variable colony morphology. No sexual reproductive structures were detected, but chlamydospores were frequently observed. The complete genome of an isolate of the lineage was sequenced with a size of 52.3 Mb including 14 707 gene models. Based on morphology and phylogenetic analysis, we propose the novel species Darksidea phi, sp. nov. Metabarcoding data showed that D. phi distribution and relative abundance were not limited to semiarid regions or a specific grass species, suggesting low host specificity among graminoids. This new species, D. phi, expands the distribution of the genus in the United States beyond prior reports from arid regions. 

KEYWORDS:

• Andropogon
• Bouteloua
• dark septate endophytes
• fungal biogeography
• Illumina sequencing
• plant symbionts
• Schizachyrium
• 1 new taxon

ACKNOWLEDGMENTS

Isolation of Darksidea cultures was possible due to sampling efforts and processing by Anny Chung, Terri Billingsley Tobias, Terry Torres-Cruz, Cedric Ndinga Muniania, Paris Salazar-Hamm, Shane Mason, and Adeyemi Olanrewaju. The authors would like to thank past and current members of the Fungal Ecology Laboratory at Western Illinois University for the help provided to process the samples.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

SUPPLEMENTARY MATERIAL

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Additional information

Funding

The research presented in this paper was supported by NSF-DEB no. 1457309 to Dr. Jumpponen, no. 1619935 to Dr. Herrera, no. 1457002 to Dr. Porras-Alfaro, and no. 1456955 to Dr. Rudgers, and by the U.S. Department of Energy (DOE) Biological and Environmental Research Division through a Science Focus Area grant to Dr. Dunbar (F255LANL2018) and Dr. Cheryl Kuske (F260LANL2013). This research was partly supported by the National Research, Development and Innovation Office, Hungary (NKFIH KH-130401 and K-139026), the ELTE Thematic Excellence Program 2020 by National Research, Development and Innovation Office (TKP2020-IKA-05), and the János Bolyai Research Scholarship of the Hungarian Academy of Sciences to Dániel G. Knapp. This material is based upon work supported by the National Science Foundation (A.P.-A.). Any opinion, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.