Commelinaceomyces, gen. nov., for four clavicipitaceous species misplaced in Ustilago that infect Commelinaceae

ABSTRACT

A fungus causing false smut in the flowers of Murdannia keisak (Commelinaceae, Commelinales, Monocots) in Japan was morphologically identical to Ustilago aneilematis. The fungus infected ovaries of most flowers of host plants. Infected flowers were filled with yellow to orange thick-walled conidia that became olivaceous green at maturity. However, multilocus phylogenetic analysis of DNA sequences (18S, 28S, translation elongation factor 1α [TEF], the largest [RPB1] and the second largest [RPB2] subunit of RNA polymerase II) showed that the fungus belonged to the tribe Ustilaginoideae (Clavicipitaceae, Hypocreales, Ascomycota). Microscopic examination showed that the fungus developed conidia at the apex of conidiogenous cells, in contrast to other species in the Ustilaginoideae that develop conidia pleurogenously. A new genus, Commelinaceomyces, is formally proposed in the Ustilaginoideae to accommodate this fungus. Four species previously misplaced in Ustilago (Ustilaginales, Basidiomycota) are transferred to Commelinaceomyces, including the type of the genus, C. aneilematis, on Murdannia keisak. This is the first report of a clavicipitaceous species infecting host plants in the Commelinaceae.

KEYWORDS:

• Clavicipitaceae
• host jump
• Metarhizium
• Murdannia keisak
• Ustilaginoidea usambarensis
• Ustilago aneilematis
• 5 new taxa

ACKNOWLEDGMENTS

We thank Dr. Yousuke Degawa for providing a sample of U. usambarensis and Dr. Yuuri Hirooka for giving us advice on treating the sample. Dr. Alistair McTaggart is thanked for informative discussion. We also thank the herbaria curators at KRA (Herbarium of the Jagiellonian University in Kraków, Poland), SAPA (Herbarium of the Faculty of Agriculture, Hokkaido University, Sapporo, Japan), and WA (Herbarium of the University of Warsaw, Poland) for their help in finding type specimens.

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Funding

This work was supported by the Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research (KAKENHI) (grant number 16K07238).