2001 Volume 42 Issue 5 Pages 461-478
Morphological and molecular phylogenetic analyses were conducted on 12 strains of Fusarium, deposited in MAFF as F. subglutinans（≡F.moniliforme var. subglutinans≡F.sacchari var. subglutinans) or Fusarium sp. because they formed aerial conidia in false heads in the dark. These strains were resolved as three distinct species within the Gibberella fujikuroi species complex. A new species, F. fractiflexum, and two species new to Japan, F. circinatum and F. concentricum, are described and illustrated and their morphological features are discussed. Fusarium fractiflexum, isolated from diseased yellow leaf spots of Cymbidium spp., is differentiated from other fusaria based on its yellowish colonies and aerial conidia formed in false heads in the dark and in zigzag-like conidial chains under black light. Japanese strains of F. circinatum also formed elongate, coiled sterile hyphae. Phialidic aerial conidia with a pointed apex and a wedge-shaped base were found in F. concentricum cultured under black light and represent a new diagnostic character of the species, in addition to colonies with alternating concentric rings when cultured on PDA. Based on DNA sequences of the β-tubuiln gene and two other loci, strains of F. fractiflexum were resolved phylogenetically as members of the Asian clade of the G. fujikuroi species complex. In addition, Japanese strains of F. circinatum and F. concentricum were phylogenetically identical to the ex-type strains.
