Detection and phylogenetic analysis of mating type genes of Ophiosphaerella korrae

Portions of the mating type genes from Ophiosphaerella korrae (J. Walker & A.M. Smith) R.A. Shoemaker (= Leptosphaeria korrae J. Walker & A.M. Smith), a pathogenic fungus of grasses, were examined by PCR (polymerase chain reaction). For nine isolates of O. korrae from North America, both mating type genes were amplified, demonstrating that both MAT idiomorphs are detectable in this homothallic ascomycete. Amplified fragments from three isolates were sequenced, and parsimony analyses of MAT1 nucleotide and protein sequences placed O. korrae in the basal position of a clade of Phaeosphaeriaceae and Pleosporaceae, whereas the MAT2 nucleotide and protein data placed O. korrae in a clade with Pleosporaceae. The internal transcribed spacer (ITS) and 18S ribosomal DNA of O. korrae were also sequenced. The 18S sequences had insufficient variability to resolve the placement of O. korrae, whereas the ITS data placed it in Phaeosphaeriaceae. A total evidence analysis of Dothideomycetes with 18S, ITS, and MAT data placed O. korrae alongside Phaeosphaeria species, with moderate bootstrap support. However, the Kishino–Hasegawa test did not demonstrate this topology to be significantly different from one where O. korrae was placed with Pleosporales. Although O. korrae does not belong in Leptosphaeria based on ITS data, MAT data do not strongly support its placement in Phaeosphaeriaceae.