PHYLOGENETIC RELATIONSHIP AMONG SEVERAL LEPTOSPHAERIA SPECIES BASED ON THEIR RIBOSOMAL DNA-SEQUENCES

The sequences coding for the 18s and 5.8s ribosomal RNAs and their int ernal transcribed spacers (ITS1 and ITS2) from isolates of Eve Leptosp haeria species were amplified by PCR and sequenced. Phylogenetic analy sis of these sequences indicated that, with the exception of L. bicolo r, Leptosphaeria species are closely related. There were two distinct lineages among species of Leptosphaeria, one represented by two weakly virulent isolates of L. maculans and the other by L. microscopica, L. nodorum and L. doliolum. The highly virulent isolate of L. maculans w as not placed definitively in either lineage and may represent an addi tional branch of the genus. The sugarcane pathogen L. bicolor was foun d to be less closely related to the other Leptosphaeria species than t o Alternaria alternata and Pleospora herbarum, and is likely to be a r epresentative of a different genus among the Pleosporales.