Sensitive detection of whole-genome differentiation among closely-related species of the genus Fusarium using DNA-DNA hybridization and a microplate technique.

We developed a new system for detection of whole-genome differentiation using DNA-DNA hybridization, and tested its sensitivity with three closely-related Fusarium species. We compared DNA-DNA relatedness to nucleotide sequence homologies of five genetic regions between each of five strains of three Fusarium species. DNA-DNA relatedness by our system was 16.2-86.6%. Sequence homologies of 18S rDNA, rDNA cluster region from ITS1 to 28S rDNA, β-tub, EF-1α and lys2 were 100.0, 99.0-100.0, 96.7-100.0, 95.1-99.4, and 94.7-100.0%, respectively. Our system could clearly detect differentiation between closely-related fungal species which have very similar morphological-characteristics, and exhibit little diagnoses in nucleotide sequences. Our results suggest that this system is a good tool for identification and phylogenetic analysis of closely-related fungal species.