[Identification of fungi using DNA sequences: an approach to identify Fusarium species isolated from domestic unpolished rice].

Molecular approaches are being developed to provide for the rapid and objective identification of fungi. We attempted the identification of Fusarium species by a genetic analysis to validate practically the utility of a molecular approach for fungal identification and to reveal its limitations, and sequenced three regions, the 5' end of the 28S rRNA gene (D2 region) and the internal transcribed spacer 1 and 2 (ITS1 and ITS2) regions, in the rRNA genes. The DNA sequences of 38 Fusarium strains isolated from domestic unpolished rice were compared for similarity with entries in the GenBank. Based on this comparison, it was estimated that all these three regions, as a minimum, must be compared with the database to identify Fusaria at the species level. According to the combinations of sequences in the three regions, the 38 isolates were classified into 13 groups. Out of the 13 groups, 6 groups (20 isolates in total) could be identified as definite species based only on the sequence data. For the other 6 groups (17 isolates in total), candidate species were limited on the basis of the sequence similarity, and then the isolates were identified at the species level with the aid of morphology. Only one isolate could not be identified. These results verified that DNA sequence comparison with the GenBank database is useful for the identification of Fusarium species.