Lopadostoma, Oligostoma, and some Rosellinia specimens from the herbarium of the Swiss Federal Institute of Technology (ZT): the value of early fieldwork and the importance of keeping fungal collections

BACKGROUND

Morphology, hosts, and collecting sites of fungi assessed from herbarium material of special interest deserve to be brought to the attention of mycologists.

RESULTS

Specimens of Lopadostoma and Oligostoma deposited at ZT are briefly described and listed to expand the knowledge about their distribution. Three yet unmentioned Rosellinia collections are reported. One could be identified as R. mastoidiformis, a second as R. neblina; both are known only from the type collections. The third one seems to be a yet undescribed taxon and is formally described as R. schueppii.

CONCLUSIONS

These observations emphasize the importance of keeping fungal collections and highlight the importance of field work and contributions by early mycologists.

Identification of Rosellinia species as producers of cyclodepsipeptide PF1022 A and resurrection of the genus Dematophora as inferred from polythetic taxonomy

Rosellinia (Xylariaceae) is a large, cosmopolitan genus comprising over 130 species that have been defined based mainly on the morphology of their sexual morphs. The genus comprises both lignicolous and saprotrophic species that are frequently isolated as endophytes from healthy host plants, and important plant pathogens. In order to evaluate the utility of molecular phylogeny and secondary metabolite profiling to achieve a better basis for their classification, a set of strains was selected for a multi-locus phylogeny inferred from a combination of the sequences of the internal transcribed spacer region (ITS), the large subunit (LSU) of the nuclear rDNA, beta-tubulin (TUB2) and the second largest subunit of the RNA polymerase II (RPB2). Concurrently, various strains were surveyed for production of secondary metabolites. Metabolite profiling relied on methods with high performance liquid chromatography with diode array and mass spectrometric detection (HPLC-DAD/MS) as well as preparative isolation of the major components after re-fermentation followed by structure elucidation using nuclear magnetic resonance (NMR) spectroscopy and high resolution mass spectrometry (HR-MS). Two new and nine known isopimarane diterpenoids were identified during our mycochemical studies of two selected Dematophora strains and the metabolites were tested for biological activity. In addition, the nematicidal cyclodepsipeptide PF1022 A was purified and identified from a culture of Rosellinia corticium, which is the first time that this endophyte-derived drug precursor has been identified unambiguously from an ascospore-derived isolate of a Rosellinia species. While the results of this first HPLC profiling were largely inconclusive regarding the utility of secondary metabolites as genus-specific chemotaxonomic markers, the phylogeny clearly showed that species featuring a dematophora-like asexual morph were included in a well-defined clade, for which the genus Dematophora is resurrected. Dematophora now comprises all previously known important plant pathogens in the genus such as D. arcuata, D. bunodes, D. necatrix and D. pepo, while Rosellinia s. str. comprises those species that are known to have a geniculosporium-like or nodulisporium-like asexual morph, or where the asexual morph remains unknown. The extensive morphological studies of L.E. Petrini served as a basis to transfer several further species from Rosellinia to Dematophora, based on the morphology of their asexual morphs. However, most species of Rosellinia and allies still need to be recollected in fresh state, cultured, and studied for their morphology and their phylogenetic affinities before the infrageneric relationships can be clarified.

Recommendations for competing sexual-asexually typified generic names in Sordariomycetes (except Diaporthales, Hypocreales, and Magnaporthales)

With the advance to one scientific name for each fungal species, the generic names in the class Sordariomycetes typified by sexual and asexual morphs are evaluated based on their type species to determine if they compete with each other for use or protection. Recommendations are made for which of the competing generic names should be used based on criteria such as priority, number of potential names changes, and frequency of use. Some recommendations for well-known genera include Arthrinium over Apiospora, Colletotrichum over Glomerella, Menispora over Zignoëlla, Microdochium over Monographella, Nigrospora over Khuskia, and Plectosphaerella over Plectosporium. All competing generic names are listed in a table of recommended names along with the required action. If priority is not accorded to sexually typified generic names after 2017, only four names would require formal protection: Chaetosphaerella over Oedemium, Diatrype over Libertella, Microdochium over Monographella, and Phaeoacremonium over Romellia and Togninia. Concerning species in the recommended genera, one replacement name (Xylaria benjaminii nom. nov.) is introduced, and the following new combinations are made: Arthrinium sinense, Chloridium caesium, C. chloroconium, C. gonytrichii, Corollospora marina, C. parvula, C. ramulosa, Juncigena fruticosae, Melanospora simplex, Seimatosporium massarina, Sporoschisma daemonoropis, S. taitense, Torpedospora mangrovei, Xylaria penicilliopsis, and X. termiticola combs. nov.

Morphological studies in Rosellinia (Xylariaceae): the first step towards a polyphasic taxonomy

More than 90 species are accepted in the xylariaceous genus Rosellinia. Thorough morphological characterisation of all known species will provide a taxonomic hypothesis that can be later tested by DNA sequence analysis. Exploratory analyses of ascospore morphology, shape of ascus apical structure, and anamorph genus suggest six morphological groups in the genus.

Fungal endophytes from the leaves and twigs of Quercus ilex L. from England, Majorca and Switzerland

Leaves of Quercus ilex taken from sites in England, Majorca and Switzerland have been studied to detect the influence of the geographic position of the host within and outside its native range on the composition of its endophytic fungal assemblages. Samples of stem tissue of Q. ilex collected from the Swiss trees were also studied to confirm tissue-specific differences. Sixty different fungal taxa were isolated, but only 28 were frequent. Of the total number of isolates from the leaves from the Swiss, British and Spanish sites 87%, 31% and 63%, respectively, were coelomycetes. Four species of Phomopsis, which includes Phyllosticta ilicina (=Phomopsis ilicina v. d. Aa, ined.), were the most frequent endophytes of leaves and were either absent or rare in the twig units. Two distinct kinds of sterile mycelia were common in twigs. Swiss and Spanish trees possessed fungal assemblages distinct from those present in Britain. Naturalized stands were distinguished from native stands by the presence of rather cosmopolitan and non-specific fungal taxa, rare or absent in the samples collected in the native stands. Samples derived from the native stands were colonized by more host-specific fungi. The relative frequency of two sterile mycelia in the Swiss and Spanish sites determined their separation. Phyllosticta (Phomopsis) ilicina, the most numerous leaf colonizer, was virtually absent from the bark and the xylem. The frequent occurrence of coelomycetes as endophytes of woody trees is briefly discussed.

Taxonomic position of Gremmeniella abietina and related species: a reappraisal

A comparative study of isolates and their corresponding herbarium specimens of Gremmeniella spp. from pine, spruce, and balsam fir, of Ascocalyx laricina from larch, and of Ascocalyx abietis from balsam fir was conducted using morphological and cultural characteristics as well as electrophoresis tests on 12 and 10 – 15% gradient polyacrylamide gels. In addition, the conidia and the ascospores of the specimens were treated with 4′,6-diamino-2-phenylindole to determine the number of nuclei per cell. Ascocalyx abietis is quite distinct in the morphology of its anamorph and in its cultural characteristics from all other samples studied. The specimens from larch differ from the others by their 2-celled ascospores and their cultural characters. Among specimens from pines and from Picea and Abies, minor morphological and cultural differences were found. The electrophoresis tests confirm the differences observed in the cultural studies. The statistical analysis of the results supports the following classification of the specimens studied: within Gremmeniella abietina, two varieties are recognized, a var. typical, with the known "European" and "North American" races from Pinus and the "Asian" race from Abies sachalinensis, and a new variety, var. balsamea, comprising the isolates from Picea and Abies (Québec). A new combination is proposed in Gremmeniella for Ascocalyx laricina. Ascocalyx abietis is retained as a separate genus.