Meliniomyces, a new anamorph genus for root-associated fungi with phylogenetic affinities to Rhizoscyphus ericae (≡ Hymenoscyphus ericae), Leotiomycetes

Abstract

Abstract Sterile fungi isolated from surface-sterilized roots of the Ericaceae, and hypothesized to be conspecific based primarily on restriction fragment length polymorphisms, were provisionally named as Variable White Taxon (VWT). In preliminary resynthesis trials with Vaccinium myrtilloides or V. vitis-idaea, isolates did not form typical ericoid mycorrhizas. Additional isolates obtained from roots of the Orchidaceae, Pinaceae, Betulaceae and Salicaceae, and given informal names such as Sterile white 1 (SW1), were thought to represent the same taxon based on cultural similarities. To evaluate conspecificity and infer phylogenetic affinities, partial nuclear ribosomal DNA sequences were determined. Parsimony analyses supported a species level distinction for VWT/SW1 and indicated that the fungus is placed within the species complex referred to as the “ Hymenoscyphus ericae aggregate” which includes H. ericae ( Leotiomycetes ), many unnamed taxa and Cadophora finlandica. The new genus and species Meliniomyces variabilis is proposed to accommodate this root-associated fungus to facilitate discussion and information retrieval, and to provide a foundation for additional experimental work. Although isolates are sterile in culture, they can be identified by morphological characters in conjunction with ribosomal internal transcribed spacer (ITS) sequence data. The mycorrhizal status of M. variabilis is not yet clear. In prior published results, strains demonstrated no or some colonization with ericoid and ectomycorrhizal hosts but did not form true ectomycorrhizas. ITS analyses indicated that the “ H. ericae aggregate” includes several other well-supported clades putatively named as Meliniomyces species. Representative strains were examined morphologically for two of these species, described as M. vraolstadiae and M. bicolor. Both include ectomycorrhizal mycobionts of the “ Piceirhiza bicolorata ” morphotype. Rhizoscyphus ericae is accepted as the appropriate name for H. ericae. Taxonomic novelties: Meliniomyces Hambleton & Sigler anam. gen. nov., Meliniomyces variabilis Hambleton & Sigler sp. nov., Meliniomyces bicolor Hambleton & Sigler sp. nov., Meliniomyces vraolstadiae Hambleton & Sigler sp. nov.