The genus Asteromella (Fungi: Ascomycota) in Poland

The critical revision of 59 Asteromella species occurring in Poland is presented, based primarily on specimens from Poland, as well as selected herbarial materials from France, Germany, Italy, Latvia, Lithuania, Romania, Slovakia, Switzerland and Ukraine. Some exsiccata, including types of Asteromella carlinae Petr., Asteromella ludwigii Petr., Asteromella ovata Thum., Asteromella petasitidis Petr., Depazea agrimoniae Lasch, Mycosphaerella agrimoniae Syd., Phyllosticta borszczowii Thum., Phyllosticta cicutae Lind, Phyllosticta eupatoriicola Kabat & Bubak, Phyllosticta pleurospermi Died., Phyllosticta salicina Kabat & Bubak, Phyllosticta senecionis-nemorensis Săvul. & Sandu, Phyllosticta wandae Namysl. were also studied. Each species is accompanied by the information pertaining to host spectrum, morphology of conidiomata, conidiophores, conidiogenous cells and conidia, distribution in Poland and globally, as well as information on synanamorphs and teleomorph, if present. Two species, Asteromella moeszii Ruszkiewicz-Michalska & Mulenko spec. nov. on Pulmonaria obscura and Asteromella rupprechtii Ruszkiewicz-Michalska spec. nov. on Agrimonia eupatoria are described, based on Polish specimens. A new name, Asteromella huubii Ruszkiewicz-Michalska nom. nov., is proposed to replace Asteromella angelicae (Sacc.) Moesz ex Bat. & Peres. Nine Phyllosticta and two Depazea species were redisposed into Asteromella : Asteromella acetosae (Sacc.) Ruszkiewicz-Michalska, comb. nov., Asteromella adoxicola (Lasch) Ruszkiewicz-Michalska, comb. nov., Asteromella alnicola (C. Massal.) Ruszkiewicz-Michalska, comb. nov., Asteromella bacilloides (Dominik) Ruszkiewicz-Michalska, comb. nov., Asteromella prunellae (Ellis & Everh.) Ruszkiewicz-Michalska, comb. nov., Asteromella garbowskii (Gucevic) Ruszkiewicz-Michalska, comb. nov., Asteromella lysimachiae (Allesch.) Ruszkiewicz-Michalska, comb. nov., Asteromella populina (Fuckel) Ruszkiewicz-Michalska, comb. nov., Asteromella salicina (Kabat & Bubak) Ruszkiewicz-Michalska, comb. nov. Neotype of Asteromella bacilloides and a lectotype of Asteromella adoxicola are designated. Nine species reported in the literature are not confirmed to occur in Poland; this includes two species that need to be recollected [ Asteromella scabiosae (Kalymb.) Vanev & Aa and Asteromella mali (Briard) Boerema & Dorenb.)], as dried specimens are scarce and deficient. Affinity of Asteromella confusa (Bubak) Petr. to Asteromella vs. Phoma is briefly disputed. New records and new data on the distribution of Asteromella species in Latvia, Poland, Slovakia, Switzerland and Ukraine are also provided. Three species are reported as new to Polish funga: Asteromella prunellae , Asteromella melampyrina and Asteromella moeszii .


Asteromella in a molecular era
For several reasons, fungi classified in Asteromella appear to be a group that has been neglected in modern mycology. First, most authors have followed the logical principle of "one fungus -one name", even prior to being formally introduced to the Melbourne Code in 2011 [56,57]. Secondly, at the basis of the application of this principle to Asteromella-like species lies the common conviction of the participation of all such fungi in the fertilization process [2,5,[58][59][60][61][62][63]. This generally-accepted assumption relies mostly on four premises: (i) small size of spores, (ii) their inability to germinate and to infect the host, (iii) the coincidence of spermogonia with asco-and conidiomata, (iv) the high morphological resemblance of spermogonia to young ascomata. However, only in a small number of cases has the fertilizing role of Asteromella spores been confirmed in field experiments or observed in the culturebased studies of Mycosphaerella species [24][25][26][27]. The unreliability of co-habitation is high, however, as demonstrated already by Klebahn in 1918 [20]. Recently, this unreliability has further increased, with reports demonstrating joint occurrence of diverse Mycosphaerella species, e.g., in a single leaf lesion of Eucalyptus [64,65]. In the newest revision of the Ramularia endophylla complex, Videira et al. [66] indicate that the role played by the Asteromella spermatial state in the development of the species still needs to be understood.
A third reason for the limited taxonomic interest in Asteromella fungi results from problems related to their culturing. Species which were attempted to cultivate did not germinate on any kind of the wide spectrum of cultural media used (e.g., [50,67,68]). However, the number of tested species remains scant. Tests have been conducted almost exclusively for those species that were already confirmed as spermatial states of Mycosphaerella. The majority of species, only presumably spermatial, were not tested with respect to growth in axenic cultures.
Modern genetic methods have delivered new insights into the taxonomy of many anamorphic fungi. DNA sequence-data have proven to be an extremely useful tool for integrating different morphs of a holomorph [69]. Examples concern many ascomycetous taxa including Mycosphaerella s. l. as well as its segregates, Septoria and Ramularia (e.g., [66,[70][71][72]). In fact, the complex of Mycosphaerella and its anamorphs has recently been widely studied; roughly 35 000 sequences generated to date are available in the GenBank database [73]. In contrast, the molecular data available for species listed under Asteromella name remain limited in the GenBank database [73]. These concern two economically important species: A. brassicicola (Chevall.) Boerema & Kesteren and A. pistaciarum Bremer & Petr. as well as two taxa recently excluded from the genus by de Gruyter et al. [16]: Paraconiothyrium tiliae (F. Rudolphi) Verkley & Gruyter and Plenodomus lupini (Ellis & Everh.) Gruyter, Aveskamp & Verkley. A number of endophytic and leaf litter-isolated Asteromella sp. sequences has also been contributed by different authors [73]. No data are available on Phyllosticta species that supposedly belong to Asteromella.
The elucidation of the role of Asteromella fungi in the life cycle of ascomycetous taxa as well as the tangled issue of host specificity require genetic and experimental studies that extend beyond the scope of the current study. Most likely, the culture-based approach is as promising as a molecular one, because the characteristics of Asteromella states hitherto studied in vitro were completely congruent with those observed in vivo.

Synonyms, classification and asexual/sexual links
Up to seven genera are listed as synonyms of Asteromella by different sources [4,10,13,14,74]. First, Petrak [28] stated that the monotypic genus Stictochorellina, described by him a year earlier, is identical to Asteromella. Petrak [28] also assumed Asteromella to be a simplified Stictochorella Höhn. Of these two, only the latter was listed as a synonym of Asteromella in the compendium of fungal genera in 1931 [75]. Five out of 15 Stictochorella names are classified in Asteromella and two others were at least temporarily included in the latter genus (according to Index Fungorum [13]). Later, Ciferri [76] provided another synonym of Asteromella by reallocating Phyllonochaeta solani Gonz. Frag. & Cif., the type species of the monotypic genus Phyllonochaeta. In Sutton's "Nomenclature of generic names proposed for Coelomycetes" [74], two other names were added to the list of synonyms: Apiosporella and Aplosporidium, both of which were introduced by Spegazzini for a new genus in a single paper from 1912 [77]. The newly described monotypic genus Apiosporella was already an illegitimate homonym for Apiosporella Höhn. from 1909 and Apiosporella Speg. from 1910. On subsequent pages, Spegazzini [77] corrects the name twice, first in erratum, where Haplosporidium is indicated as the correct name of the new genus. Secondly, the name Aplosporidium was applied instead of Haplosporidium in the general index to the species mentioned in this and the previous five parts of the series of publications on fungi of Argentina [77]. It is worth noting that in 1910 Haplosporidium Speg. had already been illegitimate (homonym of Haplosporidium Caullery & Mesnil from 1899).
In the only survey of the genus worldwide by Vanev and Aa [10], Plectophoma Höhn. and Porterula Speg. were also listed as synonyms of Asteromella. Except for Phyllonochaeta, the view of Vanev and Aa [10] is followed by the Index Fungorum database [13], while in My-coBank [14], Apiosporella/Aplosporidium is not listed among Asteromella synonyms.
Following the classic approach of anamorph classification, Melnik proposed in 1986 Asteromellaceae, i.e., the Asteromella-based family in the Coelomycetes class [78]. According to Cannon and Kirk [79], the family is currently included into synonyms of Didymosphaeriaceae Munk (currently in Pleosporales, Pleosporomycetidae [80]). Most authors classify Asteromella species together with Mycosphaerella in Mycosphaerellaceae (e.g., [81,82]), a family in Capnodiales, Dothideomycetidae, Dothideomycetes, Pezizomycotina, Ascomycota [80]. However, in the available literature, the name Asteromella is also associated with taxa other than Mycosphaerella. In course of a recent attempt to classify asexual genera in a natural biological system of fungi [83], Asteromella and Asteromella-like species were listed in four different entries (Fig. 2). The core group of species (primarily described in Asteromella or reallocated from Phyllosticta, Phoma and Ascochyta) is referred to as the genus incertae sedis within Dothideomycetes (Ascomycota) [83]. Asteromella-like species are listed as associated with the genera Gillotia Sacc. & Troter, Dothidella Speg. and Asterinella Theiss.
The Asteromella-like asexual state of Gillotia was noted by Arx and Müller [81]. The genus Dothidella shares Stictochorella anamorphs with Asteromella, although only a part of the species described in Stictochorella was reallocated in Asteromella (according to Index Fungorum [13]). The connection of Asteromella-like fungi with Asterinella likely resulted from a typographical error, as anamorphs of Asterinales were classified in Asterostomella Speg. [84]. In recent critical evaluations of ascomycetes [1,85] and in the revision of Asterinales in particular [84], Asteromella is no longer listed among the names of asexual morphs of Microthyriaceae.
According to Crous et al. [82], Asteromella species are spermatial states of Mycosphaerella s. l. taxa belonging to the former Mycosphaerella section Caterva and section Mycosphaerella having Ramularia asexual morphs (= Mycosphaerella Johanson s. str.) [66]. The analysis of data on synanamorphs associated (co-occurring) with Asteromella species in the type materials (Appendix 1) reveals that Asteromella fungi had been recorded either with Ramularia or Septoria morph. This is congruent with the earlier assumption of Aa and Vanev [5], as well as recent results of molecular studies that have proven Ramularia and Septoria to be different clades of Mycosphaerella s. l. [55,72]. The only exception is Asteromella (= Phyllosticta) buphthalmi, described by Allescher [86] as co-occurring with Ramularia buphthalmi. The later verification of the holotype also revealed the presence of Septoria buphthalmi and resulted in its inclusion in a group of presumed synanamorphs of A. buphthalmi [5].
In total, 216 Asteromella species are not regarded as associated with any other morph. Among the 47 species of known anamorphic associations, 20 names are linked to Septoria taxa (including Phloeospora), 16 to Ramularia, seven to Passalora/Cercospora, two to Phyllosticta and one each to Stagonospora and Pseudocercosporella. According to original species diagnoses and later revisions of type specimens [5], 56% of Asteromella species (142 out of 262) co-occurred with their sexual morphs, predominantly those classified in Mycosphaerella s. l. In many of these cases, no specific species could be indicated, as only immature, presumably mycosphaerellean ascomata were observed. Moreover, in the case of some host families, more than one Mycosphaerella species is described on the host genus or family, mostly with no information on its spermatial state. For the remaining of Asteromella species (120), no sexual morphs are indicated in original descriptions, secondary collections or reported in later studies of holotypes.
Thirty-one species of Asteromella have been listed as co-existing with both asexual and sexual morphs. However, in the majority of cases (18 species), an assumption was made based only on immature mycosphaerella-like ascomata or ascomatal primordia present in type materials [5].

Ecology and host-plant relationships
The host criterion has been one of the basic criterions for the delimitation of Asteromella species, despite not being a stable rule; this is true for 41 host families, primarily dicots from subtropic-and tropical areas. More than a single species has been described for 46 out of the 87 host families containing Asteromella hosts (Fig. 3). For six families, association with more than nine Asteromella species have been reported. The highest number of Asteromella species has been described on hosts from highly differentiated and circumglobally-spread families: Asteraceae and Fabaceae, followed by Apiaceae, Ranunculaceae, Rosaceae and Lilia ceae. However, neither host specificity nor the identity of morphologically-uniform species occurring on diverse hosts within the same genus occurring at different continents have been discussed or analysed in the literature until now.
Worldwide, six species are referred to as polyphagous: Asteromella artemisiae, A. longissima, A. maculiformis, A. osteospora, A. ovata and A. vulgaris [10]. As already noted, Asteromella ovata was wrongly reported on hosts from two families. Host lists for the rest of the above-listed species include data pertaining to different varieties, forms or states (ana-and teleomorph), although their genetic connections have yet to be proven. Data on A. artemisiae exclusively concern the hosts of its supposed teleomorph, i.e., Leptosphaeria artemisiae; the exact host of the Asteromella-state, to date only observed in culture, is not listed in the diagnosis [87]. Hosts of A. longissima include species reported for its basionym Sphaeria longissima and synonym Phoma longissima. In the case of A. osteospora, species hosting var. samaricola (Fraxinus), as well as hosts (e.g., Morus and Rhamnus) from Saccardo's secondary collections from PAD, were incorporated into the species host spectrum. Similarly, the fabaceous host of the Asteromella vulgaris forma gleditschiae triacantis Thüm. was included in the host spectrum of Crataegus-associated A. vulgaris. This seems illogical in light of the overall host-based taxonomy of this genus and the numerous redispositions of other subspecific taxa into new species.
Plurivory of A. maculiformis resulted from the merging of several Phyllosticta species into that of Asteromella and the different supraspecific taxa of its presumed sexual morph (Mycosphaerella punctiformis). Nevertheless, Asteromella maculiformis has raised less doubt in terms of its plurivory, as it was traditionally limited to broadleaved tree hosts in temperate zones. However, the results of a recent genetic study of Ramularia endophylla Verkley & U. Braun (the current name for Mycosphaerella punctiformis) yielded new data on the species heterogeneity and host spectrum of its segregates, i.e., R. vizellae Crous and R. unterseheri Videira & Crous [66]. It has been shown that the two latter species, R. vizellae in particular, have broad host spectrum that include trees and shrubs (Aceraceae, Betulaceae, Caprifoliaceae, Fagaceae, Hippocastanaceae, Rosaceae and Tiliaceae) as well as herbaceous plants (Brassica, Lotus, Phaseolus). Ramularia endophylla has been limited to Quercus-and Castanea-derived isolates. The role of the Asteromella state in the life cycle of R. endophylla has not been proven, nor has the spermatial state of R. vizellae and R. unterseheri been reported [66]. However, when a genetic connection of Ramularia and Asteromella is assumed, the host-specificity of Asteromella shall be questioned.

Study objectives
The aim of this study was to present the complete characteristics of Asteromella species recorded in Poland and to consider the identity of related Phyllosticta, Ascochyta and Depazea taxa deposited in reference collections in Poland. Morpho-anatomical analyses and cultural attempts were applied for this purpose. In the course of preparing for this monograph, many inconsistences and errors were found in literature-based and internet-accessible information; wherever possible, these were corrected. Thus, the Polish data are presented against a background of a critical worldwide list of names applicable to Asteromella (Appendix 1). ig. 4 The main areas of Poland surveyed (numbering in accordance with Tab. 1).

Tab. 1
The data origin: main areas surveyed as represented by exsiccata and published data.

Historical survey of Polish studies
Mycocoenological studies of microfungal occurrence in plant communities yielded the most abundant data on Asteromella species in Poland. Initiated by Majewski's study in Kampinos National Park [121], these studies were carried out until the end of the twentieth century and included the following national parks: Białowieża NP [122,123], Ojców NP [124,125], Pieniny NP [126], Poleski NP [127,128], Słowiński NP [129,130], Tatra NP ( [131] and the literature cited therein) as well as geographic regions like the Bug River Valley [132,133], Lublin Upland [134], Małopolska Upland [135] and Częstochowa Upland [136] (see [137,138] for a list of papers and plant communities studied). Asteromella (Phyllosticta) species were reported in the majority of these studies, the exception being papers concerning fungi in Kampinos NP [121], Lublin and Małopolska Uplands [134,135], and early reports from Białowieża NP [122] and Słowiński NP [129,130]. Most of the data on the occurrence of Asteromella species in Poland were listed in the literature-based checklist of Polish micromycetes in 2008 [139]. The most recent records hail from studies conducted in the Biebrza and Słowiński national parks [140][141][142].

Ecology and distribution
The current study delivers limited data on the ecology of Asteromella species, as neither experiments nor long-term observations were carried out in the field. Fresh materials were collected from diverse plant communities, in habitats that are to various degrees influenced by man-made disturbances, e.g., in forests, meadows, grasslands and in anthropogenic areas of cities. The highest species number and diversity were recorded in communities of deciduous forests.
The majority of Polish specimens of Asteromella species were collected in autumn, primarily in September and October. This corresponds to observations made by Higgins [22][23][24], Dring [25] and Brezhnev ( [26,27]). However, the formation of conidiomata is related to plant phenology, rather than directly to the season of the year. In the case of plants occurring for a short period during the growing season, Asteromella conidiomata were formed earlier, that is, in summer rather than autumn (e.g., A. adoxicola and A. convallariae). The conidiomata were often accompanied by immature ascomata and ascomatal primordia filled with parenchymatous cells. The co-occurrence of Asteromella conidiomata and its supposed asexual morphs was revealed in the case of many species.
The highest number of Asteromella species was observed for the representatives of Rosaceae, Asteraceae, Ranunculaceae and Apiaceae; this was not surprising, as these families are the most species-rich taxa among Polish flora. They are also known to host the highest number of Asteromella species worldwide (see Appendix 1). The majority of other host families represented in Polish materials were associated with between one-to-three Asteromella species.
The overall distribution of Asteromella species collected and reported from Poland is presented in Fig. 4, with more detailed information given in Tab. 1, together with the primary sources of data, i.e., literature or reference collections. However, the table and map do not include a number of localities that provided single records/species. The areas indicated in Tab. 1 and Fig. 4 were not evenly rich in Asteromella species/records. Białowieża and Biebrza national parks (area No. 3), Łęczna-Włodawa Lake District (No. 6), central Poland (No. 5) and Kraków-Częstochowa Upland (No. 7) belong to parts of Poland with the highest numbers of species/records. In course of this study, some attempts were made to complement the knowledge of distribution of Asteromella species and some unexplored or underexplored areas were surveyed. However, some of these areas should still be regarded as poorly recognized and in need of additional research (e.g., Gorce National Park, Roztocze National Park, Tatra National Park, Kampinos National Park, Warmia and Mazury, Western Pomerania and Lubuskie Province).

Morphological and anatomical characters
The descriptions of the majority of species include a limited set of characters, i.e., the size of conidiomata (primarily diameter) and conidia. More precise and detailed information concerning the characters of the conidiomatal wall, conidiophores and conidiogenous cells is available almost exclusively for species reallocated to Asteromella by Aa and Vanev [5].
Asteromella species develop predominantly on the living leaves of plant hosts and rarely on elements of the perianth (e.g., Asteromella prunellae on Prunella vulgaris). In the majority of species, the fungus causes weak disease symptoms, i.e., stains, leaf spots and discoloration. In the case of some old herbarial specimens, the colours were already lost and it was not possible to characterize them. Leaf lesions generally lack a definite, coloured margin separating the inhabited and uninhabited host tissue. However, the margin is present in some species (e.g., Asteromella rosicola) and is most likely a universal reaction of the host plant, as it has also been observed in host infection by other fungal pathogens. The most stable feature observed in almost all species is the limitation of the inhabited tissue by middle-and lower level leaf-veins, which causes the angular-shaped appearance of the lesions. Such delimited areas of host tissue are often slightly darker or discoloured compared to surrounding areas and can also be thinner or thickened due to "stuffing" with abundant conidiomata. Less frequently, the conidiomata are not accompanied by leaf alterations. This was observed in species causing systemic infection of the host leaves, e.g., Asteromella ovata and A. quercifolii.
The morphology of Asteromella species is relatively uniform. Mycelium is immersed in plant tissue, hyphae are septated, branched, non-anastomosing, hyaline or pale brown to medium brown and 3-4 µm wide (Fig. 5). Conidiomata are generally pycnidial, occasionally pycnostromatic (observed only in A. aviculariae) or almost so. In some species (A. aegopodii, A. austriaca, A. convallariae and A. huubii), leaf tissue surrounding the conidiomata is densely overgrown with brown hyphae. Pycnidial conidiomata are mostly globose or subglobose, singular or aggregated in loose or dense groups, on both sides of the leaf (e.g., A. ebuli), but mostly hypophyllous. When in dense groups, they are more or less angular or multiform, confluent and conform to lesion borders. Conidiomata are immersed in leaf tissue, often with apical parts somewhat projected above the leaf surface and rarely with up to 1/3 part of conidioma elevated above the epidermis (e.g., A. maculiformis). In most cases, the emerged part comprises papilla covering ostiolum; the papilla is rarely lacking. The colour of conidiomata is diverse and to a minor extent changes with age. The colours observed include pale grey to steel-grey, pale to dark brown, sometimes with olive tinges, or black. The conidiomatal tips often have a glassy appearance due to the mass of extruding conidia, which is slimy at first, then crusty. The conidiomatal wall is composed of (2-)3-4 layers of thin-walled cells, primarily textura angularis (e.g., type species, A. ovata Thüm.). In three species (A. bacilloides, A. garbowskii and A. rosicola) textura epidermoidea was observed in studied specimens. Other than textura angularis composition of the wall was indicated in descriptions of A. ixiolirii (textura epidermoidea), A. tobira (textura prismatica), A. ungerniae (textura globulosa changing into textura prismatica) and A. intricata (textura intricata changing into textura globulosa) [5]. Further studies are needed to elucidate the importance of this feature in the taxonomy of the group.
Ostiolum is central, circular, often well-visible, up to 37 µm (at conidiomatal diameter 49.4 µm), sometimes surrounded by the clypeus-like structure made up of darker, thick-walled cells, or irregular, likely due to lysis of topical cells or their abrasion following maturing.
Conidiophores are smooth, hyaline and line the conidiomatal wall, primarily multicellular, tapered toward the apex, branched at the base, from 5 up to 20 µm long and up to 6 µm wide. In some species (e.g., A. scabiosae), conidiophores were not observed. Conidiogenous cells are enteroblastic, phialidic, hyaline, cylindrical or conical to globose or subglobose, often in rown protruding into conidiomatal cavity, primarily integrated, rarely discrete and with a single conidiogenous loci disposed apically or laterally (then below the transversal septum). The collarette and channel are small and indistinct, and were often not preserved in the specimens.
Conidia mostly form a dense, somewhat viscous mass that frequently hinders observation of conidiophores. Conidia are hyaline, one-celled, eguttulate, minute, 2-7 × 0.5-1.8 µm, 3-5 × 1-1.5 µm in average. The conidial shape is fairly uniform, primarily rod-shaped, with  a slight narrowing at the central portion, rarely cylindrical, with a width equal over the entire length of the spore and rounded ends. The features that allow for discriminating Asteromella species from other similar genera are the fine details of the morphological structure of conidiophores and conidia. The most similar to Asteromella are small-spored Phoma s. l. (Phoma and Paraphoma [143]), distinguished by a more elliptical-or ovoidal-shaped conidia and the presence of two or more guttules. The homogenous shape of conidia of the Asteromella species is a stable character when compared to the diversely shaped spores observed in vivo in single conidiomata of Phoma section Pilosa, which have very similar conidiogenous cells [cf. Phoma betae A. B. Frank and Ph. typhina (Sacc. & Malbr.) Aa [143]]. A fundamental feature that allows for the confirmation of species placement in Phoma vs. Asteromella is germination of Phoma spores on artificial media; this is because spermatial states, by definition, do not germinate. However, in the case of old herbarium specimens that also show no growth on the culture media, this is not an unambiguous test. All the species presented here, whether old or fresh specimens, were tested for the ability of germination and axenic growth and failed.

Accepted taxa, including reallocated Phyllosticta species
The host specificity of Asteromella species is accepted here. The characteristics of 59 species are based on Polish materials and additional exsiccata, including type specimens. Three species are reported from Poland for the first time: Asteromella prunellae, A. melampyrina and A. moeszii.
The majority of Asteromella species known to occur in Poland were recorded as Phyllosticta. Nine Phyllosticta and two Depazea species are redisposed into Asteromella. The new combinations are proposed for species that are not associated with asexual or sexual morph and that differ from known Asteromella species on the respective host family. New combinations are also proposed for two species previously ascribed to Mycosphaerella species, namely, Asteromella spermatial states of Mycosphaerella lysimachiae (Höhn.) Höhn. and M. populi (Auersw.) J. Schröt., which concerns Phyllosticta lysimachiae Allesch. and Ph. populina Sacc., respectively. The decision to include these Phyllosticta species in specific Mycosphaerella was not supported by experiments or genetic studies, but was instead based on the co-occurrence of diverse morphs, where the sexual one was often immature [5]. Furthermore, more than one Mycosphaerella species is known to occur on the respective hosts [59,63]. The problem regarding the insufficiently supported transfers of species and the possible taxonomic and nomenclatural consequences thereof have been recognized by many mycologists, and was recently discussed by Hawksworth [144]. As no proof of holomorphy exists in the case of the above-mentioned Phyllosticta/Asteromella species, the new combinations are proposed to re-include the species in further taxonomic research.
Nine of the species earlier reported from Poland were excluded from the primary list and are characterized in the section concerning insufficiently-studied or doubtful species. The occurrence of six among them in Poland was not confirmed (A. aviculariae, A. garrettii, A. gentianellae, A. helleboricola, A. saponariae and A. scorzonerae) and voucher specimens of two (A. mali and A. scabiosae) were extremely scarce and deficient. One species (A. confusa) raised doubts as to its taxonomical status, which could not be resolved based on the available specimens.
Details regarding the morphology of conidia-producing structures of many of the species listed here are original and provided for the first time. In cases where Polish literature reports were not associated with corresponding voucher specimens, the species are described based on voucher materials from M, B, WA, WAUF, WRSL, KRA and KRAM reference collections. In the case of Asteromella garrettii, A. helleboricola and A. scorzonerae, the descriptions provided by other authors [5,29,[145][146][147] are presented, since no exsiccata of these species were available for examination. Connections with asexual and sexual morphs are given following Vanev and Aa [10], Aa and Vanev [5], Tomilin [59] and Aptroot [63], unless stated differently. In the worldwide distribution paragraphs, summarized data from several resources [148][149][150][151][152][153][154][155] are supplemented by regional papers, information from original descriptions and own data presented here for the first time.
Notes. The position of A. maculiformis (= Phyllosticta maculiformis Sacc.) and the listed synonyms is ambiguous. Some authors consider it to be the microconidial state of polyphagous Mycosphaerella punctiformis (Pers.) Stärback [= M. maculiformis (Pers.) J. Schroet.] (see [49]); this, however, was questioned by Aa and Vanev [5]. Following Tomilin's [59] opinion, they point out that there is no confirmation of a link between A. maculiformis and M. punctiformis, which is only one of the 12 Mycosphaerella species occurring on Castanea (type host of Ph. maculiformis). However, the same authors [5] accept synonymous Ph. humeriformis, Ph. betulae and Ph. betulina as part of M. punctiformis life cycle. Assuming the identity of these anamorphs, priority should have been given to the name Phyllosticta betulina Saccardo.

Host-specific species
The following list is arranged according to the plant family of the host species. In cases where more than one Asteromella species is associated with a specific host family, the table with main characters allowing to differentiate species is provided.

Aceraceae
Single species has been reported in Poland on Acer.

Adoxaceae
Single species has been reported in Poland on Adoxa.

Asteromella adoxicola (Lasch) Ruszkiewicz-Michalska, comb. nov.
Description. Leaf lesions yellowish, irregular, without margin, becoming pale to medium brown with age. Conidiomata very scarce, spread in leaf spots, dark black, globose, 64-108.1 µm in diam., ostiolum up to 48.4 µm in diam. Conidiophores absent. Conidiogenous cells scarce or not well preserved, globose, 3.4-4 µm in diam. Conidia in very viscous mass, rodshaped, slightly curved, 5-6 × 1-1.2 µm (Fig. 8).    Notes. The most probably Septoria podagrariae Lasch is the proper name for the species as the spores of Asteromella and Septoria morphs are observed as produced in the same conidioma. The verification of the type or secondary collection that was the base of Allescher's reallocation of Sphaeria aegopodii Curr. into Phyllosticta is necessary for the final decision.

Host plants and distribution in
World distribution. Armenia, Germany [176], Italy, Poland, Ukraine.

Araceae
Single species has been reported in Poland on Acorus.

Araliaceae
Single species has been reported in Poland on Hedera.

Asteromella hederae C. Massal.
Description. Leaf lesions circular, dried, up to 5-7 mm in diam., brown near the edge, whitish toward the centre, zonated, limited with convex margin, tissue around the spots yellowed. Conidiomata black, shiny, evenly distributed in the cental part of leaf spot and in concentric lines at its periphery, amphigenous, more abundant on the upper leaf surface,

Berberidaceae
Single Asteromella species has been reported on Berberis in Poland.

Betulaceae
Two Asteromella species has been reported on hosts in the Betulaceae in Poland: one host-specific species on Alnus (see below), and one polyphagous species on Betula (see above). Description. Leaf lesions dark brown to olive brown, limited with minor leaf veins, polygonal. Conidiomata evenely distributed or aggregated in groups, amphigenous, globose, brown to black, papillate, 49.4-98.8 µm in diam., ended with erected ostiolum, up to 17.3-24.7 µm in diam. Conidiophores 1-3-celled, unbranched, 10 × 4 µm. Conidiogenous cells subglobose, 3.5 × 4 µm. Conidia rod-shaped, (2.5-)3.5-4 × 0.8-1 µm (Fig. 23).  39.1. The authority of this species was ascribed to Gusztáv von Moesz [12] who collected the type specimen in Hungary in 1940. Moesz died 15 years before the species was described and in the paper by Batista and Peres [12] there is neither acknowledgment to Moesz, nor indication of his role in the preparation of the description.

Host plant and distribution in
The name proposed by Batista and Peres [12] is, however, invalid as the species description was given in Portuguese that is in discordance with the rules of ICN [57]. Therefore, the species on Pulmonaria obscura is described here as new based on the Polish specimen.   Synanamorphs and teleomorph. Unknown. In the type collection the species co-occurs with Ramularia cylindroides Sacc. but genetic connection of the morphs was not tested. On host genus Pulmonaria a single Mycosphaerella species was described, M. pulmonariae Fakirova. No anamorphic and spermatial states of the fungus were indicated in the diagnosis [185].

Brassicaceae
Single Asteromella species has been reported on Brassica in Poland.

Synanamorphs and teleomorph.
Unknown. Two Mycosphaerella species were described in association with Euonymus but without spermatial state indicated [63].

Host plant and distribution in
World distribution. France, Germany [36], Poland, Romania, Ukraine.

Fabaceae
Two Asteromella species have been reported on Astragalus and Caragana in Poland (Tab. 7). They cannot be differentiated based on morphology itself.

Fagaceae
Single Asteromella species has been reported on Quercus in Poland. quercifolii except for lack of conidiophores in the specimen studied (Fig. 33). However, conidiogenous cells and conidia are badly preserved in that specimen.

Hippocastanaceae
Single Asteromella species has been reported on Aesculus in Poland.

Host plants and distribution in
Asteromella aesculicola (Sacc.) Petr. is treated as a synonym of Leptodothiorella aesculicola (Sacc.) Sivan. by some authors, e.g. Punithalingham [192] and it is followed by Index Fungorum database [13]. Both names are included into synonyms of Guignardia aesculi (Peck) V. B. Stewart. As emphasized by Punithalingham [192], for clarification of the taxonomic status of A. aesculicola examination of the type material is required.

Lamiaceae
Single Asteromella species has been reported on Prunella in Poland.

Liliaceae
Single Asteromella species has been reported on Convallaria and Polygonatum in Poland.

Orobanchaceae
Single Asteromella species has been reported on Melampyrum in Poland.
Synanamorphs and teleomorph. Septoria acetosae Oudem. [5]; teleomorph unknown. In the specimen LOD PF-287 at the lower leaf surface the lesions caused by Asteromella acetosae were covered with conidiomata of Ramularia rubella (Bonord.) Nannf. Six Mycosphaerella species were described on host from Rumex genus but no spermatial state of them is known [63].

Ranunculaceae
Three Asteromella species have been reported on Helleborus, Ranunculus and Trollius in Poland (Tab. 9).

Rhamnaceae
Single Asteromella species has been reported on Rhamnus in Poland.
The specimen of Phyllosticta passerinii from B reference collection (B 700015173) has a new combination A. passerinii (Fig. 46e-g) that was most probably proposed by H. Rupprecht but was never published.   (Fig. 48).   [196].

Host plant and distribution in
World distribution. Denmark, Poland, Ukraine.

Synanamorphs and teleomorph. Unknown.
Notes. The species description is based on the isotype of Depazea agrimoniae Lasch from WRSL and the isotype of Mycosphaerella agrimoniae Syd., housed in KRA (KRA F-1941-16), which contains a number of empty conidiomata (Fig. 49). The characters of the rest of the Polish specimens studied fit the above-given characteristics.

Salicaceae
Three Asteromella species have been reported on Populus and Salix in Poland. Species reported from Populus hosts differ in the lack of conidiophores in A. osteospora, as observed in the Polish collections (Tab. 11). There are no data on conidiophores in type collection as it was not seen by Aa and Vanev [5], who however consider the species to be polyphagous. Asteromella salicina has smaller conidia than both species associated with Populus.

Tiliaceae
Single Asteromella species has been reported on Tilia in Poland. On the hosts from that genus also Asteromella tiliae (F. Rudolphi) Verkley & Gruyter was reported from Poland. The species has been recently reallocated to Paraconiothyrium [16].

Insufficiently studied and doubtful species
Nine Asteromella species reported in Poland are characterized below and arranged in alphabetical order. The corresponding specimens, as well as exsiccata were insufficient for confirming their occurrence in Poland (eight species) or to draw final conclusions about their affinity (A. confusa).

Pistacia vera
Asia: Turkey

Carlina vulgaris
Europe: Czech Republic

Europe: Czech Republic
Host family