Grouping of Colletotrichum Species in Japan Based on rDNA Sequences

Internal transcribed spacers (ITS) of the ribosomal RNA gene (rDNA) were sequenced for 236 isolates covering 25 Colletotrichum species collected in Japan. The Japanese isolates could be grouped into 20 ribosomal groups (RGs) based on the sequences of ITS1, correlating the species identified by the morphology. Colletotrichum gloeosporioides sensu lato separated into three RGs that were morphologically different. Colletotrichum destructivum, C. linicola and C. higginsianum were possibly conspecific. Colletotrichum dematium sensu lato including C. capsici and other species that produce falcate conidia except for graminicolous ones were separated into three RGs that were difficult to distinguish morphologically. In the phylogenetic study using ITS2 and the 28S rDNA domain 2 region, topologies compiled by neighbor-joining and maximum-parsimony methods were almost the same, reflecting the conidial morphology. The phylogenetic group 1 (PG1) produced conidia with acute ends, e.g., C. acutatum, C. destructivum and C. graminicola; PG2 produced those with obtuse ends, e.g., C. gloeosporioides, and C. orbiculare. Colletotrichum theae-sinensis, which produced the smallest conidia, was grouped as PG3, far from other species, indicating it should not belong to Colletotrichum. Grouping and phylogenetic analysis using ribosomal DNA was an effective tool to classify and identify Colletotrichum species without using morphology.