遺伝子塩基配列を用いての Fusarium 属菌の同定と分子系統学的位置付けに関する研究

Species of the genus Fusarium are well-researched in many fields, and a commonly problem by researchers interested in Fusarium species is the probable taxonomic system and the identification method of this genus. The traditional taxonomic system for fungi has been proposed based on the mainly morphological species concept, including the genus Fusarium. Recently, many researchers have applied molecular markers to examine the taxonomy and identification of Fusarium species. This review shows some recent findings from our studies about molecular phylogeny and identification of Fusarium species based on analyses with nucleotide sequences. First, the genetic markers were evaluated for identifying Fusarium isolates by calculation of the homologies with pairwise comparison of all tested strains, and of the ratio of nucleotide substitution rate. It was suggested that aminoadipate reductase gene (lys2) is notionally the most appropriate genetic marker for identifying isolates among the six genes examined. Second, actual identification of food-borne isolates of the genus Fusarium based on the nucleotide sequence homology was performed, and the results were evaluated. In terms of accuracy and ease, b-tubulin gene, not lys2, is the most useful genetic maker among the six genes examined. Finally, the genetic markers were evaluated for the phylogenetic analysis of Fusarium species. It was suggested the lys 2 have a singular evolutionary history than other genes. To obtain a reliable phylogeny for Fusarium species, the lys2 sequences were excluded from the dataset, and the species tree was inferred. The reliable Fusarium species tree was reconstructed, and some interesting relationships were newly described.