Japanese species of Alternaria and their species boundaries based on host range.

To clarify the diversity of plant-parasitic species in Japan, diseased samples were collected, and fungal isolates established in culture. We examined 85 isolates representing 23 species distributed in 14 known sections based on conidial morphology and DNA phylogeny. Three species were found to be new, and . Furthermore, a lectotype was designated for . , and epitypes for . , . , . , and . . Species boundaries of isolates were also clarified by studying phenotypes and determining host ranges. and related species in sect. were recognized as distinct species owing to their host specificity. Among the species infecting , the pathogenicity of . and a novel species, . ex , were confirmed as host specific. Another novel species, . proved to be host specific to . was recognized as a large-spored species in sect. , being host specific to spp. On the other hand, the experimental host ranges of three morphologically and phylogenetically distinct species infecting (. , . , and . ) showed almost no differences. and . were even found on non-host plants. In general, host ranges of species correlated with morphology and molecular phylogeny, and combining these datasets resulted in clearer species boundaries.