In: Sydowia 74, (2021): 163-174; ISSN 0082-0598, DOI 10.12905/0380.sydowia74-2021-0163, Published online on November 11, 2021

Belonium coroniforme Rehm (Helotiales), a highly specialized muscicolous ascomycete on Orthotrichaceae and Leucodon

Peter Döbbeler, Arnold Büschlen, Jan Eckstein & Andrin Gross

1 Ludwig-Maximilians-Universität München, Systematische Botanik und Mykologie, Menzinger Str. 67, 80638 München, Germany
2 Lötschenmattstraße 10, 8912 Obfelden, Switzerland
3 Arnoldiweg 20, 37083 Göttingen, Germany
4 Swiss Federal Research Institute WSL, SwissFungi, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland
* e-mail: jan.eckstein@octospora.de

Döbbeler P., Büschlen A., Eckstein J. & Gross A. (2021): Belonium coroniforme Rehm (Helotiales), a highly specialized muscicolous
ascomycete on Orthotrichaceae and Leucodon. – Sydowia 74: 163–174.

The ascomycete Belonium coroniforme Rehm (Helotiales) forms both orange apothecia and apothecia-like conidiomata (sporodochia) on corticolous moss species of the genera Lewinskya, Orthotrichum and Ulota (Orthotrichales), as well as Leucodon (Hypnales). Both the apothecia and the sporodochia are restricted to the female shoot apices (perichaetia), producing a compact mycelial wedge within the host stems. The fungal morphs can occur together or separately on shoot apices of the same or different plants. Infection prevents the normal development of sporophytes, which means that capsules with mature spores are not produced, thus reducing the host’s fertility. In contrast, except for the infected shoot apices, the gametophytic plants retain their green healthy appearance and continue to grow by subapical innovation. Belonium coroniforme is sporadically documented in Europe and also occurs in Nepal and Tunisia. Apart from having a hyphomycetous anamorph, it is characterized by a clear preference for orthotrichalean mosses and by occupying a distinct microniche. This high specialization has never been observed in muscicolous apothecial ascomycetes before. Sequence data from eight different collections taken from five different host species did not reveal any variation within the ITS1, ITS2 and LSU region of the rDNA, with inconclusive generic placement. Isolation attempts of the fungus from infected moss parts and ascospore germination experiments were not successful on standard malt-extract agar medium, strongly suggesting an obligate biotrophic lifestyle. The aim of this article is to present a comprehensive description of B. coroniforme and its host-parasite relationship as well as to provide initial genetic resources for the species.

Keywords: Bryophilous fungi, conidiomata, microniche, reduction of fertility, sex specificity.