A new genus and species, Blastosporium persicolor, is described and illustrated from leaves of mildewed tobacco. It is characterised by branched, septate hyphae from which arise macronematous, unbranched or spaced branched conidiophores and mono- or polyblastic conidiogenous cells that produced solitary and blastocatenate, obovoid, oblong, ellipsoidal, allantoid, broad fusiform to irregular, unicellular, hyaline conidia. The phylogenetic analyses, based on the combined sequence data from the small and large nuclear subunit ribosomal DNA (SSU and LSU), placed B. persicolor in the Leotiomycetes class, Helotiales order.

Ascomycota, Pezizomycotina, phylogeny, Nicotiana tabacum

The Kingdom Fungi contains a huge number of species, which continues to rise with more collections. With the advance in the studies of DNA sequence data, the fungal classification system has been updated over the years. Many described species obtained new taxonomic status after the molecular data and have been processed. Leotiomycetes is a large class in Ascomycota and has potential taxonomic value relating to the ecology and biology. The traditional classification of Leotiomycetes at high levels has experienced considerable challenges with the inclusion of the molecular techniques in systematics studies. For example, early research accepted five orders, 21 families and about 510 genera in the Leotiomycetes on the basis of both traditional classification and molecular phylogenetic studies (Eriksson 2005, Kirk et al. 2001), but a recent study reported a new classification of Leotiomycetes, including 11 orders, 44 families and about 590 genera (Wijayawardene et al. 2018) and this classification also lacks sufficient DNA sequence data. In Leotiomycetes, the order Helotiales, one of the largest non-lichen-forming ascomycetous groups, is composed of fungi of diverse morphology and ecology. Of these, members of the Helotiales thrive in various ecosystems and cover a broad range of niches and helotialean fungi have been found as plant pathogens, endophytes, nematode-trapping fungi, mycorrhizae, ectomycorrhizal parasites, fungal parasites, terrestrial saprobes, aquatic saprobes, root symbionts and wood rot fungi (Wang et al. 2006).

During a survey of fungi growing on mildewed tobacco leaves, an unknown fungus was found. Based on its morphological characters and DNA sequence data, it is proposed as a new asexual genus and species, Blastosporium persicolor.

To determine the phylogenetic placement of this species, Blastosporium persicolor was analysed with species from 7 classes, Leotiomycetes, Arthoniomycetes, Dothideomycetes, Eurotiomycetes, Orbiliomycetes, Pezizomycetes and Geoglossomycetes (Wang et al. 2006). By Bayesian analysis, the new genus was placed in the Helotiales, Leotiomycetes. In the tree, B. persicolor grouped with the Cudonia-Spathularia clade and Vibrissea clade, but the placement did not receive strong support. Therefore, we have temporarily designated this species as a new genus and family incertae sedis.

In the Helotiales, many genera, such as Bulgaria Fr. (Bulgariaceae), Rutstroemia P. Karst. (Rutstroemiaceae) and Hegermila Raitv. (Hyaloscyphaceae), were only observed as sexual morphs, but Neofabraea H.S. Jacks (Dermateaceae) and Articulospora Ingold (Helotiaceae) were observed as having asexual and sexual morphs (Chen et al. 2015, Wijayawardene et al. 2018, Wang et al. 2015a). In this study, we just observed the asexual morph of B. persicolor.

Based on ITS sequence data, B. persicolor is 88% similar to the genus Tetracladium De Wild. (T. marchalianum De Wild. as the type species), which was placed in the Helotiales and family incertae sedis. Moreover, Blastosporium shares some morphological features with Tetracladium as pale yellow and compact colonies and hyphae branched, septate and hyaline and both Blastosporium and Tetracladium sporulated abundantly on natural substrates (Sati et al. 2009, Wang et al. 2015b). However, B. persicolor is obviously distinct from the genus Tetracladium by the size and shape of conidia.

By molecular phylogeny analysis, Blastosporium belongs to the order Helotiales that currently contains 27 families (Wijayawardene et al. 2018). Moreover, members of the Helotiales cover a broad range of niches, such as plant pathogens, endophytes and aquatic hyphomycetes. Blastosporium persicolor was discovered from mildewed tobacco; therefore, it may be a plant pathogen.

This work was financed by the National Natural Science Foundation Program of PR China (31570023, 31770026). We are grateful to two reviewers for critically reviewing the manuscript and for providing helpful suggestions to improve this paper.