Fusarium fractiflexum sp. nov. and two other species within theGibberella fujikuroi species complex recently discovered in Japan that form aerial conidia in false heads

Morphological and molecular phylogenetic analyses were conducted on 12 strains ofFusarium, deposited in MAFF asF. subglutinans (≡F. moniliforme var.subglutinans≡F. sacchari var.subglutinans) orFusarium sp. because they formed aerial conidia in false heads in the dark. These strains were resolved as three distinct species within theGibberella fujikuroi species complex. A new species,F. fractiflexum, and two species new to Japan,F. circinatum andF. concentricum, are described and illustrated and their morphological features are discussed.Fusarium fractiflexum, isolated from diseased yellow leaf spots ofCymbidium 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 ofF. circinatum also formed elongate, coiled sterile hyphae. Phialidic aerial conidia with a pointed apex and a wedgeshaped base were found inF. 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-tubulin gene and two other loci, strains ofF. fractiflexum were resolved phylogenetically as members of the Asian clade of theG. fujikuroi species complex. In addition, Japanese strains ofF. circinatum andF. concentricum were phylogenetically identical to the ex-type strains.