Dermea was protected against its synonym, Foveostroma, due to its well-circumscribed generic concept and more frequent use. We describe and illustrate Dermea chinensis sp. nov. based on its morphological characteristics and a molecular analysis of the internal transcribed spacer (ITS) and large subunit (LSU) sequence data. Dermea chinensis is isolated from Betula albosinensis with sexual and asexual morphs and can be distinguished from D. molliuscula on Betula trees by its aseptate and wider ascospores. The connection between the two morphs is proved based on sequence data. Here, we describe the asexual morph of D. pruni for the first time based on morphological and molecular data from the same host and country of origin, and compare it with other species of Prunus.

Betula, Dermateaceae, new species, Prunus

Dermea Fr. (Dermateaceae, Helotiales) was first proposed based on D. cerasi (Fries, 1825), which is the sexual Asexual morph of the type species of Micropera Lév. (Léveillé, 1846) and Foveostroma DiCosmo (DiCosmo 1978), namely M. drupacearum and F. drupacearum, respectively. Due to the well-circumscribed concept and its more frequent use, Dermea was protected as the legitimate generic name (Johnston et al. 2014).

Groves (1946) accepted 16 species in Dermea and proposed a key for this genus based mainly on the characteristics of apothecia, asci, ascospores, and conidia, along with host associations. Subsequently, Dermea tumifaciens (Ramakrishnan & Ramakrishnan, 1948), D. pruni (Groves, 1951), D. grovesii (Reid & Pirozynski, 1966), D. rhytidiformans (Funk & Kuijt, 1970), D. tetrasperma (Funk, 1976), D. abietinum (Johnston et al., 2014), D. boycei (Johnston et al., 2014), D. stellata (Johnston et al., 2014), and D. persica (Mehrabi et al., 2018) were added to this genus. However, D. balsamea and D. peckiana, which were accepted by Groves (1946), were later synonymised with D. abietinum and D. stellata, respectively (Johnston et al. 2014). Thus, 23 species were included in this genus before this study.

Dermea is a well-characterized genus with hard, leathery, dark brown to black apothecia; cylindrical to clavate-cylindrical, usually eight-spored asci; and ellipsoid-fusiform to ellipsoidal, hyaline to yellowish-brown, aseptate to 3-septate ascospores (Groves 1946; Mehrabi et al. 2018). The asexual Asexual morph of Dermea contains rather diverse conidiomatal structures, which usually accompany the apothecia (Groves 1946; Mehrabi et al. 2018). Additionally, two kinds of conidia are characterized: elongate-fusiform to sickle-shaped macroconidia and bacillary to filiform microconidia (Groves 1946; Mehrabi et al. 2018).

Dermea species are generally considered highly host-specific (Groves 1946, 1951). The plant genus Prunus is the major host for Dermea, with D. cerasi, D. padi, D. prunastri, and D. pruni described from them (Groves 1946, 1951). However, ascospores in D. pruni are larger than those from the other three species (Groves 1951). Dermea cerasi, D. padi, and D. prunastri can be easily distinguished by the macroconidial and microconidial dimensions (Groves 1946). Among these four species, D. cerasi, D. padi, and D. prunastri were recognized based on both sexual and asexual fruiting bodies (Groves 1946), but D. pruni was proposed only with a sexual Asexual morph based on a specimen (Teng #3352, preserved in the herbarium of the University of Michigan) collected from China (Groves 1951). Hence, the re-collection of D. pruni specimens aiming for an asexual Asexual morph from the original host and country seems meaningful. Additionally, few sequence data are available for most Dermea species, and considering that the host associations may be incorrect and that many geographical areas are still insufficiently studied, the synonymies and actual numbers of Dermea species are still unclear.

Dermea species were considered pathogenic to their hosts (Groves 1951; Abeln et al. 2000). For example, D. abietinum (syn. D. balsamea) caused hemlock dieback (Dodge 1932) and D. prunastri was considered the cause of greengage plums die-back (Dowson 1913). However, members of Dermea have not been recently reported to cause serious plant diseases.

During our fungal collection surveys conducted in China, we collected several Dermea specimens from two species of tree, Betula albosinensis and Prunus cerasifera f. atropurpurea. We identified fungi species using both morphological and molecular approaches; as a result, a novel species and the asexual Asexual morph of D. pruni are described herein for the first time.

In this study, we collected several Dermea specimens from China and morphologically and molecularly examined them. Dermea chinensis from Betula trees is introduced, which can be distinguished from D. molliuscula by aseptate and wider ascospores, and from other species by host association (Table 2). Four Dermea species, D. cerasi, D. padi, D. prunastri, and D. pruni have been reported from Prunus trees (Groves 1946, 1951). These four species can be obviously distinguished by both morphological and molecular approaches. We update the asexual Asexual morph and molecular data of D. pruni.

Table 2.Download as CSV 

Comparison of phenotypic characters of currently accepted Dermea species.

Species	Host genera	Ascospores dimension (µm); septation	Macroconidia dimension (µm); septation	Microconidia dimension (µm)	Reference
D. abietinum	Abies; Tsuga	20–30 × 6–8; 1–4-celled	60–75 × 4–5; 1–4-celled	11–22 × 1.0–1.5	Groves 1946; Johnston 2014
D. acerina	Acer	13–20 × 5–8; 1–4-celled	15–25 × 5–8; 1-celled	6–10 × 1.0–2.0	Groves 1946
D. ariae	Sorbus	12–18 × 3–5; 1–4-celled	15–20 × 2.0–4.0; 1–2-celled	NA	Groves 1946
D. bicolor	Amelanchier	12–15 × 3–4; 1–2-celled	15–20 × 2.5–4.0; 1–2-celled	NA	Groves 1946
D. boycei	Pseudotsuga	16–28 × 4–7; 1–4-celled	42–56 × 3–4; 1–4-celled	8–14 × 1–2	Funk 1967; Johnston 2014
D. cerasi	Prunus	15–20 × 5–7.5; 1–4-celled	40–60 × 2.5–4.5; 1–2-celled	12–23 × 1.0–1.5	Groves 1946
D. chinensis	Betula	14–19 × 7–9; 1-celled	54–78 × 3.2–4.2; 1-celled	NA	This study
D. chionanthi	Chionanthus	18–25 × 7–9; 1–2(–4)- celled	25–35 × 5–7; 1–2-celled	NA	Groves 1946
D. grovesii	Picea	16.5–21.5 × 6–5; 1–3- celled	60–95 × 6.5–8; 7–11-celled	NA	Reid and Pirozynski 1966
D. hamamelidis	Hamamelis	15–20 × 5.0–7.5; 1–4- celled	18–25 × 4.5–6.0;1–2-celled	NA	Groves 1946
D. libocedri	Libocedrus	15–20 × 6–8; 1–4-celled	42–65 × 4–6; 1–4-celled	10–18 × 1.0–1.5	Groves 1946
D. molliuscula	Betula	15–20 × 4–7; 1–4-celled	50–75 × 2.5–3.5; 1–4-celled	7–12 × 1.0–1.5	Groves 1946
D. padi	Prunus	15–20 × 5–7; 1–4-celled	20–28 × 2.5–4.0; 1–2-celled	4–6 × 1.5	Groves 1946
D. persica	NA	NA	20–25 × 2.5–3.5; 1-celled	NA	Mehrabi et al. 2018
D. piceina	Picea	12–14 × 6–8; 1–2(–4)- celled	22–40 × 3–5; 1–4-celled	9–15 × 1.0–1.5	Groves 1946
D. pinicola	Pinus	13–18 × 5.0–7.5; 1–2- celled	30–40 × 4–6; 1–4-celled	NA	Groves 1946
D. prunastri	Prunus	15–20 × 5.0–7.5; 1–4- celled	20–30 × 5–7; 1-celled	7–10 × 1.5	Groves 1946
D. pruni	Prunus	15–20 × 8–10; 1(–4)-celled	62–95 × 2–3.5; 2-celled	NA	Groves 1951; This study
D. rhytidiformans	Abies	18–28 × 8–11; 1-celled	25–65 × 3.5–5.5; 1–4-celled	10–22 × 1.5	Funk and Kuijt 1970
D. stellata	Nemopanthus	12–18 × 4–6; 1–2(–4)- celled	40–55 × 2.5–4.5; 1–2-celled	8–13 × 1.5–2.0	Groves 1946; Johnston 2014
D. tetrasperma	Pseudotsuga	14–17 × 4–6; 1-celled	15–22 × 5–6; 1-celled	NA	Funk 1976
D. tulasnei	Fraxinus	15–20 × 6–8; 1–4-celled	25–40 × 6–8; 1-celled	NA	Groves 1946
D. tumifaciens	Capparis	13 × 5.4 / 10–19 × 4.8–9.6; 2-celled	18 × 7 / 15–22 × 4–9; 2- celled	NA	Ramakrishnan and Ramakrishnan 1948
D. viburni	Viburnum	14–18 × 3.5–5.5; 1–2- celled	30–45 × 2.5–4.0; 1–4-celled	NA	Groves 1946

The genus Pezicula is a phylogenetically close to Dermea species and has recently been confirmed based on an ITS-28S-16S rDNA analysis (Mehrabi et al. 2018). However, Pezicula is characterized by typically bright-coloured, yellowish to ochraceous, more fleshy-waxy apothecia, broader and more clavate asci, and more broadly ellipsoid to oblong-ellipsoid or ovoid ascospores (Grove 1946). Our phylogenenetic analysis of Dermea and related genera based on the combined ITS and LSU sequence data (Fig. 1) showed that Pezicula is well-supported as a separate clade with high values (MP/ML = 96/98). Dermea was thought to be a monophyletic group (Abeln et al. 2000), but Dermea was not well-supported, as D. persica was included in the analysis (Mehrabi et al. 2018). We added additional DNA sequence data in our study (Fig. 1), which indicates that Dermea is not monophyletic.

Species of Dermea are well-circumscribed by morphological characteristics. However, only 10 species (Table 1) are currently characterized by molecular data, and most species remain unconfirmed by phylogenetic examination. Hence, DNA data from type or ex-strains and newly obtained collections are essential in subsequent taxonomic work.

This study was financed by the National Natural Science Foundation of China (Project No.: 31670647). We are grateful to Chungen Piao and Minwei Guo (China Forestry Culture Collection Center (CFCC), Chinese Academy of Forestry, Beijing) for support with strain preservation during this study.