Magnaporthiopsis cynodontis, a novel turfgrass pathogen with widespread distribution in the United States

ABSTRACT

The genus Magnaporthiopsis of Magnaporthaceae (Magnaporthales, Sordariomycetes, Ascomycota) contains species that are predominantly necrotrophic pathogens, often producing simple hyphopodia and dark, ectotrophic runner hyphae on plant roots and stems during colonization. Fungal isolates from turfgrass roots with dark and ectotrophic runner hyphae were examined and identified based on morphological, biological, and phylogenetic analyses. Maximum likelihood and Bayesian methods were implemented to obtain phylogenetic trees for partial sequences of the 18S nuc rDNA, ITS1-5.8S-ITS2 nuc rDNA internal transcribed spacer, and 28S nuc rDNA regions, and of the minichromosome maintenance complex 7 (MCM7), largest subunit of RNA polymerase II (RPB1), and translation elongation factor 1-alpha (TEF1) genes. Our isolates consistently formed a distinct and highly supported clade within Magnaporthiopsis. These findings were reinforced by common and distinctive biological and morphological characters. Additionally, we conducted pathogenicity evaluations and demonstrated the ability of this fungus to colonize roots of ultradwarf bermudagrass, one of its native hosts, via ectotrophic, dark runner hyphae, causing disease symptoms including root discoloration and reduced root and shoot mass. Altogether, our discoveries enabled recognition and description of a new species, Magnaporthiopsis cynodontis, which has widespread distribution in the United States.

KEYWORDS:

• Magnaporthaceae
• multilocus phylogeny
• pathogen
• taxonomy
• 1 new taxon

ACKNOWLEDGMENTS

We thank Nicole Brochard for her technical assistance throughout the project, and L. P. Tredway for providing isolates of Magnaporthiopsis poae. We also thank K. Scott, D. Petrella, E. Watkins, S. Tirpark, and R. Buckley for providing diseased turfgrass samples.

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Additional information

Funding

Funding for this work was provided by the O. J. Noer Turfgrass Research Foundation, the Mississippi Agricultural and Forestry Experiment Station, the National Institute of Food and Agriculture, U.S. Department of Agriculture, Hatch project under accession number 213130, and the National Science Foundation (DEB 1452971).