Tuberculina-Helicobasidium: Host specificity of the Tuberculina-stage reveals unexpected diversity within the group¹

Abstract

Tuberculina species are mitosporic parasites of rust fungi. It was demonstrated recently that Tuberculina represents the asexual life stage of the plant-parasitic genus Helicobasidium. Here we reveal the host specificities of Tuberculina and Helicobasidium species on rust fungal hosts by means of infection experiments and molecular analyses. We inoculated species of the rust genera Chrysomyxa, Coleosporium, Cronartium, Gymnosporangium, Puccinia, Tranzschelia and Uromyces with conidia and with basidiospores of Helicobasidium longisporum and H. purpureum and with conidia of Tuberculina maxima, T. persicina and T. sbrozzii. In addition we analyzed base sequences from the nuclear ITS region of 51 Tuberculina and Helicobasidium specimens collected in the field together with the sequences from the Tuberculina infections obtained by infection experiments. The resulting data show that at least six monophyletic lineages are within the Tuberculina/Helicobasidium-group that can be unambiguously distinguished by combining molecular and morphological characters and by specific host spectra of the Tuberculina-stage. This diversity opens up new vistas on the evolution of this exceptional mycoparasitic-phytoparasitic fungal group.

• Helicobasidium
• host specificity
• infection experiments
• ITS
• Tuberculina
• molecular phylogeny
• mycoparasitism
• Urediniomycetes

We thank W. Maier, and C. Lutz for critical comments on the manuscript, M. Mennicken and H. Teppner for their endeavors to assist in the field, the anonymous reviewers for their helpful comments and the Deutsche Forschungs-gemeinschaft for financial support.