A Multilocus Phylogeny Places Hymenula cerealis (syn. Cephalosporium gramineum) in the Helotiales, Leotiomycetes

Abstract

The soilborne fungus Hymenula cerealis causes Cephalosporium stripe, a vascular wilt disease of wheat and other grasses in the United States and other wheat-producing countries where winter wheat is subjected to snow cover and frozen soil. No sexual stage is known for H. cerealis, and consequently, its phylogenetic position relative to other fungi has been difficult to establish. The purpose of this study was to conduct a multilocus sequence analysis to determine the phylogenetic position of H. cerealis. Sequence data for five genes, the internal transcribed spacer (ITS), partial large subunit nrDNA (LSU), partial RNA polymerase II second largest subunit region (RPB2), β-tubulin gene, and translation elongation factor 1-α (TEF1-α), from a diverse set of C. gramineum isolates and other related fungi was obtained from GenBank or directly from isolates in the Murray lab and used to construct maximum-likelihood and Bayesian trees. Based on phylogenetic analysis of the single LSU and β-tubulin genes, Cephalosporium gramineum is closely related to the Drepanopezizaceae and Ploettnerulaceae of Helotiales. Based on analyses of the DNA sequence of the ITS, RPB2, and TEF1-α genes, as well as the combined five-gene data set, C. gramineum belongs to the family Drepanopezizaceae, which is a sister taxon to the Ploettnerulaceae, and formed a well-supported clade (MLBP/BIPP = 95%/100%). In conclusion, H. cerealis belongs to the Helotiales, Leotiomycetes.