Erysiphe paeoniae-suffruticosae Zhao Y. Zhang & S. Y. Liu, 2025

Zhang, Zhao-Yang, Wu, Xue-Lian, Lv, Xiao-Xue, Liu, Tie-Zhi, Jin, Dan-Ni, Liu, Li, Wang, Shuang-Bao, Feng, Jing, Hsiang, Tom, Li, Yu & Liu, Shu-Yan, 2025, Discover hidden taxa of Erysiphe section Erysiphe fungi (Ascomycota, Erysiphaceae) based on morphology and multilocus phylogeny in China, MycoKeys 118, pp. 119-146 : 119-146

Erysiphe paeoniae-suffruticosae Zhao Y. Zhang & S. Y. Liu sp. nov.

Fig. 6

Etymology.

Epithet derived from the name of the host species, Paeonia × suffruticosa .

Diagnosis.

Differs from E. paeoniae in having significantly smaller chasmothecia, 78–98 (– 118) µm diam. vs. (70 –) 90–125 (– 135) µm diam., with longer appendages, 0.5–3.3 times as long as the chasmothecial diam. vs. 0.25–1 (– 2) times, and significantly different asci and ascospores, and by forming a well-supported species clade in phylogenetic ITS + 28 S + IGS as well as ITS + 28 S + IGS + RPB 2 + TUB analyses in sister position to E. paeoniae on Paeonia lactiflora .

Description.

Mycelium on stems, fruits, perianths and leaves, amphigenous, effuse, often covering the entire surface of the leaves, forming mycelial layers of uneven thickness or patches, persistent; hyphae straighten or flexuous, 4–7 µm wide; hyphal appressoria nipple-shaped to moderately lobed, solitary or in opposite pairs, often several per hyphal cell. Asexual morph: Conidiophores on top of mother cell, (22 –) 29–69 × 8–12 µm long, foot cells cylindrical, (11 –) 15–28 (– 36) × 8–10 µm (without condia), often curved at the base, few erect, followed by 0–2 mostly shorter cells; conidia single, cylindrical, long-cylindrical, doliiform, 25–48 × 12–19 µm, length / width ratio 1.4–3.8; germ tubes terminal, septate, partly forming curved aerial germ tubes, tips irregularly forked, partly long-clavate, or medium-long, swollen to club-shaped or lobed. Sexual morph: Chasmothecia scattered, produced first on the abaxial surface of the leaf and more numerous than on the adaxial surface, black-brown, hemispherical, 78–98 (– 118) µm diam.; peridium cells irregularly polygonal, 6–15 µm diam.; appendages 15–28, mycelioid, 1–2 times bifurcately branched, rarely unbranched, also forming small irregular branches or small protuberances, often 1–2 times irregularly branched apically, some small branches tending to be parallel, 0.5–3.3 times as long as the chasmothecial diam., 56–218 (– 257) µm, 0–1 - septate, smooth or rough, dark brown or light brown throughout, or only basally brown and upward becoming colorless; asci dimorphic, micro- and macro-asci mixed together in the same ascoma mostly, 3–6 in total, viz., micro-asci, ovoid, saccate, irregularly ovoid, subglobose or elongate, (14 –) 20–49 × (11 –) 18–30 µm, long-stalked, short-stalked to sessile, containing 0–1 spore, ovoid, 10–16 × 9–13 µm; macro-asci, ovoid, ellipsoid-ovoid, subglobose, saccate, 34–65 (– 69) × 19–45 (– 51) µm, long-stalked, short-stalked to sessile, containing 1–5 - spores, ascospores ovoid, ellipsoid-ovoid, 18–27 × 11–19 µm, colorless.

Holotype.

China, Shaanxi Prov. • 1; Yan’an City ; 36°37'10"n, 109°27'26"e; ca. 930 m a. s. l.; 27 Sep. 2018; Shu-Rong Tang & Li Liu leg.; on Paeonia × suffruticosa ; HMJAU -PM 92255 . Isotype: same data as for holotype; HMAS 353412 .

Host.

Paeonia × suffruticosa ( Paeoniaceae ).

Distribution.

Asia ( China and South Korea).

Additional material examined.

China, Gansu Prov. • 1; Lanzhou City ; 36°2'49"n, 103°51'14"e; ca. 1461 m a. s. l.; 20 Sep. 2018; Shu-Rong Tang & Li Liu leg.; on P. × suffruticosa ; HMJAU -PM 92256 . • 1; Lanzhou City ; 36°4'13"n, 103°48'50"e; ca. 1560 m a. s. l.; 16 Oct. 2023; Zhao-Yang Zhang & Li Liu leg.; on P. × suffruticosa ; HMJAU -PM 92254 . – Heilongjiang Prov. • 1; Mudanjiang City ; 44°35'9"n, 129°37'11"e; ca. 240 m a. s. l.; Fen-Yun Zhao, Vanninh Nguyen, Jing-Sheng Lu & Jia-Ni Li leg.; on P. × suffruticosa ; HMJAU -PM 92272 . – Jilin Prov. • 1; Changchun City ; 43°48'21"n, 125°24'17"e; ca. 1460 m a. s. l., 10 Aug. 2023; Zhao-Yang Zhang leg.; on P. × suffruticosa ; HMJAU -PM 92257 .

Notes.

Powdery mildew on Paeonia × suffruticosa was first found in South Korea and identified as Erysiphe paeoniae through combined morphology and ITS sequence analyses ( La et al. 2015). Subsequent reports from China confirmed this identification using ITS data ( Qian et al. 2016). While the anamorphic morphologies of E. paeoniae on P. × suffruticosa (designated E. paeoniae-suffruticosae ) and P. lactiflora (on E. paeoniae ) show no significant differences, their chasmothecium structures exhibit marked morphological divergence. Notably, E. paeoniae-suffruticosae possesses two distinct types of asci and ascospores, whereas E. paeoniae exhibits only a single type. The holotype of E. paeoniae (hosted on P. obovata preserved at the HMAS, Beijing) underwent morphological re-evaluation and molecular analysis; however, all sequencing attempts failed, probably due to the age of the specimen. Despite this limitation, the morphological similarity observed between E. paeoniae populations on P. obovata and P. lactiflora supports the authenticity of E. paeoniae on its type host. Significant morphological differentiation between E. paeoniae-suffruticosae and E. paeoniae is supported by phylogenetic analyses using ITS + 28 S + IGS, which together support recognition of E. paeoniae-suffruticosae as a distinct taxon on P. × suffruticosa (Suppl. material 1). Furthermore, in the multi-gene analysis (ITS + 28 S + IGS + RPB 2 + TUB), E. paeoniae-suffruticosae formed a distinct clade, providing additional evidence for its taxonomic distinction (Fig. 2 ).

Field surveys indicate high susceptibility of P. × suffruticosa to powdery mildew, suggesting potential broader geographic distribution of E. paeoniae-suffruticosae within China.

Figures

Figure 2. Phylogenetic tree of selected species within sect. Erysiphe based on the ITS + 28 S + IGS + RPB 2 + TUB regions. Bootstrap values greater than 60 % for the maximum likelihood (ML) analyses are displayed followed by posterior probabilities ≥ 0.70 of Bayesian inference (BI) analyses. HT = Holotype; the color box indicates new species; bold font indicates the new species obtained in this study; blue bold font indicates new record species.

Figure 6. Symptoms and morphology of Erysiphe paeoniae-suffruticosae sp. nov. on Paeonia × suffruticosa (holotype: HMJAU - PM 92255) A – D powdery layer and chasmothecia on buds, leaves and stems E hyphal appressorium F – I conidiophores J conidium K – M germ tubes N chasmothecium O peridium cells P appendage Q – Z asci (Q, R two types asci S – V micro-asci W – Z macro-asci) a micro-ascospores b macro-ascospores. Scale bars: 10 µm (E – K, O, a, b); 20 µm (L, M, P – Z); 50 µm (N).