Muribasidiospora: Microstromatales or Exobasidiales?

Characteristics of hyphal septation, cellular interaction, sporulation, cul tures and/or nuclectide sequences from the 5 ' terminal domain of the nucle ar large subunit rRNA gene of some species of Exobasidium, Microstroma and Muribasidiospora were examined and compared. Our analyses show that the ord er Microstromatales comprises Microstroma, Muribasidiospora triumfetticola and the anamorphic species Rhodotorula bacarum, R. phylloplana and Sympodio mycopsis paphiopedili, whereas Muribasidiospora hesperidium and Muribasidio spora indica are members of the Exobasidiales. Because of the high degree o f morphological divergence between Muribasidiospora triumfetticola and Micr ostroma, a new genus, Volvocisporium, and a new family, Volvocisporiaceac, of the Microstromatales are proposed. Apart from the phylogenetic implicati ons, the most interesting observations in the present work are the unusual development of the basidia, especially of the basidiospores, and the nutrie nt transport system hom the host attacking hyphae to the basidia in Muribas idiospora triumfetticola.