Multilocus phylogeny of Ophiosphaerella species causing spring dead spot of bermudagrass
N. WALKER (1), S. Marek (1)
(1) Oklahoma State University, Stillwater, OK, U.S.A.
Phytopathology 100:S131

Ophiosphaerella herpotricha, O. korrae, and O. narmari are causal agents of spring dead spot on turf-type bermudagrass (Cynodon spp. and interspecific hybrids) in the transition zone of the United States. Growing as sterile mycelia in culture, Ophiosphaerella spp. cannot be identified morphologically and few DNA sequences are available for comparison. Forty O. herpotricha, twenty-seven O. korrae and five O. narmari isolates collected from bermudagrass from throughout the U.S. were selected for this study. Three O. korrae isolates from bluegrass were also included. DNA sequences of the nuclear ribosomal small subunit (SSU), internally transcribed spacer (ITS) region, and large subunit (LSU), a region of the translation elongation factor 1α (EF1α) gene, and the second largest subunit gene of RNA polymerase II (RPB2) from each isolate were analyzed. Group I introns of various sizes often were inserted in SSU sequences at up to four positions and corresponded with the species of the isolate. SSU introns often disrupted primer sites around the ITS region, precluding its use for identification. Multilocus phylogenies clustered O. herpotricha and O. narmari into well-resolved, monophyletic clades, while O. korrae isolates clustered more loosely due to greater sequence variation. EF1α and RPB2 sequences were more useful than rDNA sequences for identifying Ophiosphaerella isolates to species.