Phylogeny of Alternaria fungi known to produce host-specific toxins on the basis of variation in internal transcribed spacers of ribosomal DNA.

The internal transcribed spacer regions (ITS1 and ITS2) of ribosomal DNA from Alternaria species, including seven fungi known to produce host-specific toxins, were analyzed by polymerase chain reaction-amplification and direct sequencing. Phylogenetic analysis of the sequence data by the Neighbor-joining method showed that the seven toxin-producing fungi belong to a monophyletic group together with A. alternata. In contract, A. dianthi, A. panax, A. dauci, A. bataticola, A. porri, A. sesami and A. solani, species that can be morphologically distinguished from A. alternata, could be clearly separated from A. alternata by phylogenetic of the ITS variation. These results suggest that Alternaria pathogens which produce host-specific toxins are pathogenic variants within a single variable species, A. alternata.