Querciphoma styphnolobii H.X. Gao & Z.X. Zhu, 2022

Gao, Hanxing, Yin, Jingyan, Li, Yu, Liu, Shuyan & Zhu, Zhaoxiang, 2022, Introducing Querciphoma styphnolobii sp. nov., the first sexual morph of Querciphoma (Leptosphaeriaceae, Pleosporales), Phytotaxa 555 (4), pp. 279-290 : 284-286

Querciphoma styphnolobii H.X. Gao & Z.X. Zhu , sp. nov. ( Figs. 2–3 )

MycoBank no.: MB 840304.

Etymology:— The epithet “styphnolobii” refers to the host plant genus Styphnolobium .

Type: — CHINA, Henan Province, Xingyang city, 34°49′N, 113°21′E, 130 m elevation, on the bark of Styphnolobium japonicum , 6 Jun 2020, Hanxing Gao 1367, HMJAU 34703 (holotype!), HMJAU 35100 (culture collection) .

Diagnosis:— Querciphoma styphnolobii is characterized by eustromatic, pycnidial conidiomata with scleroplectenchymatous cell type in the peridium, smooth, hyaline, cylindrical conidia with one middle constricted septum and muriform ascospores.

Description:—Sexual morph: Ascomata solitary, gregarious, semi-immersed to erumpent through host tissue, becoming superficial, globose, rough or hairy, dark brown to black, ostiolate, with short papilla, 100–200 × 90–190 µm (av. = 140 × 130 µm, n = 24). Ostiole central, smooth, with ostiolar canal filled with hyaline cells, 40–50 µm long, 20–30 µm diam. (av. = 45 × 25 µm, n = 10). Setae septate, brown, 42–60 µm (av. = 56 µm, n = 20). Peridium 20–60 µm (av. = 40 µm, n = 20) wide at the base, 18–50 µm (av. = 35 µm, n = 20) wide at the sides, comprising 3–6 layers, with outer layer heavily pigmented, blackish to dark brown, thick-walled, scleroplectenchymatous cells of textura angularis, cells towards the inside lighter, with inner layer composed 3–4 layers, hyaline, flattened, thin-walled cells of textura angularis, (6.5–)9.0–34(–38) × (5.0–)6.0–15 μm (av. = 18 × 9.0 μm, n = 35). Hamathecium composed of numerous, dense, cylindrical to filiform, long, cellular pseudoparaphyses, embedded in mucilage, rarely branched, septate, 1–2.5 μm wide. Asci 8-spored, bitunicate, fissitunicate, fusiform, short-pedicellate, rounded at apex with a minute ocular chamber, 86–138 × 18–21 µm (av. = 115 × 19 µm, n = 22). Ascospores biseriate, mostly ellipsoidal, muriform, 3−6 transversely eusepta, with one vertical septum, constricted at the middle septum, conical and narrow at the ends, surrounded by a mucilaginous sheath, initially hyaline, becoming light brown at maturity, 18–24 × 8–11 µm (av. = 22 × 9 µm, n = 50).

Asexual morph: Coelomycetous structures produced in culture. Conidiomata pycnidial, eustromatic, solitary, sometimes aggregated, globose to subglobose, light brown, uni- to multi-locular, with 1–3 papillate ostioles, superficial or immersed in the agar, 110–260 µm (av. = 170 µm, n = 32) wide. Conidiomata wall scleroplectenchyma, comprising of 3–4 layers of textura angularis, outermost layer brown, inner layer hyaline, 4.0–9.0 × 2.5–6.5 µm (av. = 6.0 × 5.0 µm, n = 53). Setae brown, septate, 25–87 µm (av. = 64 µm, n=20). Conidiophore cylindrical to phialide-like, hyaline, arising from the inner layers of conidioma. Conidiogenous cells holoblastic, discrete, or integrated with septate, hyaline. Conidia cylindrical, hyaline, 1(–3) septates, the septa in the middle constricted, with 2 large guttules or several tiny guttules, 12–19 × 4.0–7.0 µm (av. = 16 × 6.0 µm, n = 77).

Culture characteristics: Colony slow-growing, optimum growth at 25°C, not growing at 35°C on all media, reaching 40 mm on PDA, 55 mm on CMD, 58 mm on OA after 2 weeks at 25°C. Colonies circular, dense, slightly raised to convex, or dome-shaped, dull, surface slightly rough with small turfs, velvety to floccose; colony dark-green at the margin, grey-greenish at the center on CMD and OA, almost dark on PDA. Conidiomata only formed on OA.

Distribution and Habitat:— China, on Styphnolobium japonicum .

Discussion:— Querciphoma styphnolobii is compatible with the generic concept of Querciphoma in having eustromatic, uni- to multi-locular, pycnidial conidiomata with septate setae and a thick-walled peridium of brown to dark brown or reddish-brown, scleroplectenchymatous cells. Morphologically, the type species, Querciphoma minuta has smaller ( Q. minuta : (3.5–)4–5(–6) × 3(–3.5) µm vs. Q. styphnolobii : 12.3–19 × 4.4–7.0 µm), broadly ellipsoidal, aseptate, and brown conidia ( Crous & Groenewald 2017). Q. styphnolobii is easily distinguished by its smooth, hyaline, cylindrical conidia with mostly one middle constricted septum.

Querciphoma styphnolobii differs from Alloleptosphaeria , Pseudoleptosphaeria and Subplenodomus in the structure of the conidiomata wall (scleroplectenchyma vs. pseudoparenchymatous) ( Ariyawansa et al. 2015, Hongsanan et al. 2020). Querciphoma styphnolobii shares similar pycnidial characters with Leptosphaeria sensu stricto, Plenodomus , and Paraleptosphaeria in the scleroplectenchymatous cell type in the peridium ( de Gruyter et al. 2013, Ariyawansa et al. 2015, Wanasinghe et al. 2016, Aiello et al. 2020, Phukhamsakda et al. 2020). However, Q. styphnolobii has mostly 1-septate conidia rather than aseptate conidia ( Ariyawansa et al. 2015, Hongsanan et al. 2020).

Based on morphology, Querciphoma styphnolobii is most similar to Chaetoplea with similar black perithecial ascomata with scleroplectenchymatous cells, pycnidial conidiomata with oblong to ellipsoidal, smooth-walled conidia. However, Chaetoplea produced brown conidia and fusiform to ellipsoidal ascospores with only transverse septa ( Phookamsak et al. 2014), while Q. styphnolobii can be easily distinguished by hyaline conidia with one middle constricted septum and muriform ascospores.

Querciphoma styphnolobii also closely related to Sclerenchymomyces that was introduced by Phukhamsakda et al. (2020) which includes two species. Sclerenchymomyces jonesii (Wanasinghe, Camporesi & K.D. Hyde) Phukhams. & K.D. Hyde (2020: 43) shares similarities with Q. styphnolobii in having globose, rough or hairy ascomata, cylindrical, short-pedicellate asci, and overlapping uniseriate, ellipsoidal, muriform ascospores with conical and narrow at the ends, but the former has different aseptate and smaller conidia (3–4 × 2–2.5 μm versus 12–19 × 4.0–7.0 µm) ( Wanasinghe et al. 2016, Phukhamsakda et al. 2020). In addition, Sclerenchymomyces clematidis Phukhams. & K.D. Hyde (2020: 41) obviously differs from Q. styphnolobii in broad cylindrical to oblong, and yellowish conidia with 3 septa ( Phukhamsakda et al. 2020).

Thirteen genera of Leptosphaeriaceae were included in our phylogenetic tree ( Figure. 1 ) except Chaetoplea whose sequences are unavailable. Querciphoma styphnolobii is closely related to Q. minuta , and formed an independent lineage with high statistical support (MPBP/MLBP/BIPP = 100/100/1). In a BLASTn search of GenBank, the ITS sequence of Q. styphnolobii was 95.8% (100% query coverage) similar to Q. minuta (LG1401-MS6E) with 24 nucleotide differences from 572 base pairs (4.2%), while the LSU and SSU sequences showed 99.54% (with 96% query coverage) and 100% (with 100% query coverage) similarity to Q. minuta (CBS 105.91), respectively. Sequence analyses also confirmed our identification. Combined morphological and phylogenetic analyses confirmed our new species Q. styphnolobii as a distinct member of the genus Querciphoma . With the discovery of new species, the sexual morph of Querciphoma were supplemented. This paper also contributes to a more comprehensive update and improved identification of Querciphoma based on our collection.

Figures

FIGURE 1. Maximum parsimony phylogram reconstructed from the combined sequences of ITS-LSU-SSU-TEF1-α, showing the phylogenetic position of Querciphoma styphnolobii. MPBP equal to or above 50% (left), MLBP equal to or above 50% (middle) and BIPP equal to or above 0.9 (right) are given on the nodes. Hyphens (-) represent support values equal to or less than 50% MPBP/50% MLBP/0.90 BIPP. The type sequences are in black bold, and the strains derived in this study are in red.

FIGURE 2. Teleomorph of Querciphoma styphnolobii (HMJAU 34703, holotype) A–C. Ascomata on the substrate. D. Vertical section of ascoma. E. Ostiole. F, G. Setae. H–J. Mature asci and hamathecium. K, L. Mature asci. M, N. Asci apex. O–X. Ascospores (X in Indian ink to show the mucilaginous sheath). Scale bars:A = 1 mm; B, C = 200 μm; D–L = 20 μm; M–X = 10 μm.

FIGURE 3. Anamorph of Querciphoma styphnolobii (HMJAU 35100, holotype) A–C. Cultures after 16 days at 25°C (A: PDA. B: CMD. C: OA). D. Conidiomata on OA. E, F. Conidioma. G, H. Conidiogenous cells. I, J. Conidia. Scale bars: A–C = 1cm; D = 200 μm; E, F = 20 μm; G–J = 10 μm.